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Fischl M, Pederson A, Voglewede R, Cheng H, Drew J, Torres Cadenas L, Weisz CJC. Fast Inhibition Slows and Desynchronizes Mouse Auditory Efferent Neuron Activity. J Neurosci 2024; 44:e0382242024. [PMID: 38937103 PMCID: PMC11326868 DOI: 10.1523/jneurosci.0382-24.2024] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2024] [Revised: 06/04/2024] [Accepted: 06/11/2024] [Indexed: 06/29/2024] Open
Abstract
The encoding of acoustic stimuli requires precise neuron timing. Auditory neurons in the cochlear nucleus (CN) and brainstem are well suited for accurate analysis of fast acoustic signals, given their physiological specializations of fast membrane time constants, fast axonal conduction, and reliable synaptic transmission. The medial olivocochlear (MOC) neurons that provide efferent inhibition of the cochlea reside in the ventral brainstem and participate in these fast neural circuits. However, their modulation of cochlear function occurs over time scales of a slower nature. This suggests the presence of mechanisms that reduce MOC inhibition of cochlear function. To determine how monaural excitatory and inhibitory synaptic inputs integrate to affect the timing of MOC neuron activity, we developed a novel in vitro slice preparation ("wedge-slice"). The wedge-slice maintains the ascending auditory nerve root, the entire CN and projecting axons, while preserving the ability to perform visually guided patch-clamp electrophysiology recordings from genetically identified MOC neurons. The "in vivo-like" timing of the wedge-slice demonstrates that the inhibitory pathway accelerates relative to the excitatory pathway when the ascending circuit is intact, and the CN portion of the inhibitory circuit is precise enough to compensate for reduced precision in later synapses. When combined with machine learning PSC analysis and computational modeling, we demonstrate a larger suppression of MOC neuron activity when the inhibition occurs with in vivo-like timing. This delay of MOC activity may ensure that the MOC system is only engaged by sustained background sounds, preventing a maladaptive hypersuppression of cochlear activity.
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Affiliation(s)
- Matthew Fischl
- Section on Neuronal Circuitry, National Institute on Deafness and Other Communication Disorders, NIH, Bethesda, Maryland 20892
| | - Alia Pederson
- Section on Neuronal Circuitry, National Institute on Deafness and Other Communication Disorders, NIH, Bethesda, Maryland 20892
| | - Rebecca Voglewede
- Section on Neuronal Circuitry, National Institute on Deafness and Other Communication Disorders, NIH, Bethesda, Maryland 20892
| | - Hui Cheng
- NIDCD Data Science Core, National Institute on Deafness and Other Communication Disorders, NIH, Bethesda, Maryland 20892
| | - Jordan Drew
- Section on Neuronal Circuitry, National Institute on Deafness and Other Communication Disorders, NIH, Bethesda, Maryland 20892
| | - Lester Torres Cadenas
- Section on Neuronal Circuitry, National Institute on Deafness and Other Communication Disorders, NIH, Bethesda, Maryland 20892
| | - Catherine J C Weisz
- Section on Neuronal Circuitry, National Institute on Deafness and Other Communication Disorders, NIH, Bethesda, Maryland 20892
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2
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Zacher AC, Felmy F. Anatomy of superior olivary complex and lateral lemniscus in Etruscan shrew. Sci Rep 2024; 14:14734. [PMID: 38926520 PMCID: PMC11208622 DOI: 10.1038/s41598-024-65451-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2024] [Accepted: 06/20/2024] [Indexed: 06/28/2024] Open
Abstract
Based on the auditory periphery and the small head size, Etruscan shrews (Suncus etruscus) approximate ancestral mammalian conditions. The auditory brainstem in this insectivore has not been investigated. Using labelling techniques, we assessed the structures of their superior olivary complex (SOC) and the nuclei of the lateral lemniscus (NLL). There, we identified the position of the major nuclei, their input pattern, transmitter content, expression of calcium binding proteins (CaBPs) and two voltage-gated ion channels. The most prominent SOC structures were the medial nucleus of the trapezoid body (MNTB), the lateral nucleus of the trapezoid body (LNTB), the lateral superior olive (LSO) and the superior paraolivary nucleus (SPN). In the NLL, the ventral (VNLL), a specific ventrolateral VNLL (VNLLvl) cell population, the intermediate (INLL) and dorsal (DNLL) nucleus, as well as the inferior colliculus's central aspect were discerned. INLL and VNLL were clearly separated by the differential distribution of various marker proteins. Most labelled proteins showed expression patterns comparable to rodents. However, SPN neurons were glycinergic and not GABAergic and the overall CaBPs expression was low. Next to the characterisation of the Etruscan shrew's auditory brainstem, our work identifies conserved nuclei and indicates variable structures in a species that approximates ancestral conditions.
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Affiliation(s)
- Alina C Zacher
- Institute of Zoology, University of Veterinary Medicine Foundation, Buenteweg 17, 30559, Hannover, Germany
- Hannover Graduate School for Neurosciences, Infection Medicine and Veterinary Sciences (HGNI), Buenteweg 2, 30559, Hannover, Germany
| | - Felix Felmy
- Institute of Zoology, University of Veterinary Medicine Foundation, Buenteweg 17, 30559, Hannover, Germany.
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3
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Fischl M, Pederson A, Voglewede R, Cheng H, Drew J, Cadenas LT, Weisz CJ. Fast inhibition slows and desynchronizes mouse auditory efferent neuron activity. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2023.12.21.572886. [PMID: 38313270 PMCID: PMC10836066 DOI: 10.1101/2023.12.21.572886] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2024]
Abstract
The encoding of acoustic stimuli requires precise neuron timing. Auditory neurons in the cochlear nucleus (CN) and brainstem are well-suited for accurate analysis of fast acoustic signals, given their physiological specializations of fast membrane time constants, fast axonal conduction, and reliable synaptic transmission. The medial olivocochlear (MOC) neurons that provide efferent inhibition of the cochlea reside in the ventral brainstem and participate in these fast neural circuits. However, their modulation of cochlear function occurs over time scales of a slower nature. This suggests the presence of mechanisms that restrict MOC inhibition of cochlear function. To determine how monaural excitatory and inhibitory synaptic inputs integrate to affect the timing of MOC neuron activity, we developed a novel in vitro slice preparation ('wedge-slice'). The wedge-slice maintains the ascending auditory nerve root, the entire CN and projecting axons, while preserving the ability to perform visually guided patch-clamp electrophysiology recordings from genetically identified MOC neurons. The 'in vivo-like' timing of the wedge-slice demonstrates that the inhibitory pathway accelerates relative to the excitatory pathway when the ascending circuit is intact, and the CN portion of the inhibitory circuit is precise enough to compensate for reduced precision in later synapses. When combined with machine learning PSC analysis and computational modeling, we demonstrate a larger suppression of MOC neuron activity when the inhibition occurs with in vivo-like timing. This delay of MOC activity may ensure that the MOC system is only engaged by sustained background sounds, preventing a maladaptive hyper-suppression of cochlear activity.
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Affiliation(s)
- Matthew Fischl
- Section on Neuronal Circuitry, National Institute on Deafness and Other Communication Disorders, NIH, Bethesda, MD 20892, USA
- Current affiliation: Lafayette College, Neuroscience Program, Easton, PA 18042, USA
| | - Alia Pederson
- Section on Neuronal Circuitry, National Institute on Deafness and Other Communication Disorders, NIH, Bethesda, MD 20892, USA
- Current affiliation: The University of Texas at Austin Dell Medical School, Austin, TX 78712, USA
| | - Rebecca Voglewede
- Section on Neuronal Circuitry, National Institute on Deafness and Other Communication Disorders, NIH, Bethesda, MD 20892, USA
| | - Hui Cheng
- Bioinformatics and Biostatistics Collaboration Core, National Institute on Deafness and Other Communication Disorders, NIH, Bethesda, MD 20892, USA
| | - Jordan Drew
- Section on Neuronal Circuitry, National Institute on Deafness and Other Communication Disorders, NIH, Bethesda, MD 20892, USA
- Current affiliation: Institute for Learning and Brain Sciences, University of Washington, Seattle, WA, 98195, USA
| | - Lester Torres Cadenas
- Section on Neuronal Circuitry, National Institute on Deafness and Other Communication Disorders, NIH, Bethesda, MD 20892, USA
| | - Catherine J.C. Weisz
- Section on Neuronal Circuitry, National Institute on Deafness and Other Communication Disorders, NIH, Bethesda, MD 20892, USA
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Almassri LS, Ohl AP, Iafrate MC, Wade AD, Tokar NJ, Mafi AM, Beebe NL, Young JW, Mellott JG. Age-related upregulation of perineuronal nets on inferior collicular cells that project to the cochlear nucleus. Front Aging Neurosci 2023; 15:1271008. [PMID: 38053844 PMCID: PMC10694216 DOI: 10.3389/fnagi.2023.1271008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2023] [Accepted: 10/26/2023] [Indexed: 12/07/2023] Open
Abstract
Introduction Disruptions to the balance of excitation and inhibition in the inferior colliculus (IC) occur during aging and underlie various aspects of hearing loss. Specifically, the age-related alteration to GABAergic neurotransmission in the IC likely contributes to the poorer temporal precision characteristic of presbycusis. Perineuronal nets (PNs), a specialized form of the extracellular matrix, maintain excitatory/inhibitory synaptic environments and reduce structural plasticity. We sought to determine whether PNs increasingly surround cell populations in the aged IC that comprise excitatory descending projections to the cochlear nucleus. Method We combined Wisteria floribunda agglutinin (WFA) staining for PNs with retrograde tract-tracing in three age groups of Fischer Brown Norway (FBN) rats. Results The data demonstrate that the percentage of IC-CN cells with a PN doubles from ~10% at young age to ~20% at old age. This was true in both lemniscal and non-lemniscal IC. Discussion Furthermore, the increase of PNs occurred on IC cells that make both ipsilateral and contralateral descending projections to the CN. These results indicate that reduced structural plasticity in the elderly IC-CN pathway, affecting excitatory/inhibitory balance and, potentially, may lead to reduced temporal precision associated with presbycusis.
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Affiliation(s)
- Laila S. Almassri
- Department of Anatomy and Neurobiology, Northeast Ohio Medical University, Rootstown, OH, United States
| | - Andrew P. Ohl
- Department of Anatomy and Neurobiology, Northeast Ohio Medical University, Rootstown, OH, United States
| | - Milena C. Iafrate
- Department of Anatomy and Neurobiology, Northeast Ohio Medical University, Rootstown, OH, United States
- Department of Biological Sciences, Kent State University, Kent, OH, United States
| | - Aidan D. Wade
- Department of Anatomy and Neurobiology, Northeast Ohio Medical University, Rootstown, OH, United States
- Department of Biological Sciences, Kent State University, Kent, OH, United States
| | - Nick J. Tokar
- Department of Anatomy and Neurobiology, Northeast Ohio Medical University, Rootstown, OH, United States
| | - Amir M. Mafi
- The Ohio State College of Medicine, The Ohio State, Columbus, OH, United States
| | - Nichole L. Beebe
- Department of Anatomy and Neurobiology, Northeast Ohio Medical University, Rootstown, OH, United States
| | - Jesse W. Young
- Department of Anatomy and Neurobiology, Northeast Ohio Medical University, Rootstown, OH, United States
| | - Jeffrey G. Mellott
- Department of Anatomy and Neurobiology, Northeast Ohio Medical University, Rootstown, OH, United States
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Wicke KD, Oppe L, Geese C, Sternberg AK, Felmy F. Neuronal morphology and synaptic input patterns of neurons in the intermediate nucleus of the lateral lemniscus of gerbils. Sci Rep 2023; 13:14182. [PMID: 37648787 PMCID: PMC10468510 DOI: 10.1038/s41598-023-41180-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2023] [Accepted: 08/23/2023] [Indexed: 09/01/2023] Open
Abstract
The lateral lemniscus encompasses processing stages for binaural hearing, suppressing spurious frequencies and frequency integration. Within the lemniscal fibres three nuclei can be identified, termed after their location as dorsal, intermediate and ventral nucleus of the lateral lemniscus (DNLL, INLL and VNLL). While the DNLL and VNLL have been functionally and anatomically characterized, less is known about INLL neurons. Here, we quantitatively describe the morphology, the cellular orientation and distribution of synaptic contact sites along dendrites in mature Mongolian gerbils. INLL neurons are largely non-inhibitory and morphologically heterogeneous with an overall perpendicular orientation regarding the lemniscal fibers. Dendritic ranges are heterogeneous and can extend beyond the nucleus border. INLL neurons receive VGluT1/2 containing glutamatergic and a mix of GABA- and glycinergic inputs distributed over the entire dendrite. Input counts suggest that numbers of excitatory exceed the inhibitory contact sites. Axonal projections indicate connectivity to ascending and descending auditory structures. Our data show that INLL neurons form a morphologically heterogeneous continuum and incoming auditory information is processed on thin dendrites of various length and biased to perpendicular orientation. Together with the different axonal projection patterns, this indicates that the INLL is a highly complex structure that might hold many unexplored auditory functions.
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Affiliation(s)
- Kathrin D Wicke
- Institute for Zoology, University of Veterinary Medicine Foundation, Hannover, Buenteweg 17, 30559, Hannover, Germany
| | - Leon Oppe
- Institute for Zoology, University of Veterinary Medicine Foundation, Hannover, Buenteweg 17, 30559, Hannover, Germany
| | - Carla Geese
- Institute for Zoology, University of Veterinary Medicine Foundation, Hannover, Buenteweg 17, 30559, Hannover, Germany
| | - Anna K Sternberg
- Institute for Zoology, University of Veterinary Medicine Foundation, Hannover, Buenteweg 17, 30559, Hannover, Germany
| | - Felix Felmy
- Institute for Zoology, University of Veterinary Medicine Foundation, Hannover, Buenteweg 17, 30559, Hannover, Germany.
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Tureček R, Melichar A, Králíková M, Hrušková B. The role of GABA B receptors in the subcortical pathways of the mammalian auditory system. Front Endocrinol (Lausanne) 2023; 14:1195038. [PMID: 37635966 PMCID: PMC10456889 DOI: 10.3389/fendo.2023.1195038] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/27/2023] [Accepted: 07/24/2023] [Indexed: 08/29/2023] Open
Abstract
GABAB receptors are G-protein coupled receptors for the inhibitory neurotransmitter GABA. Functional GABAB receptors are formed as heteromers of GABAB1 and GABAB2 subunits, which further associate with various regulatory and signaling proteins to provide receptor complexes with distinct pharmacological and physiological properties. GABAB receptors are widely distributed in nervous tissue, where they are involved in a number of processes and in turn are subject to a number of regulatory mechanisms. In this review, we summarize current knowledge of the cellular distribution and function of the receptors in the inner ear and auditory pathway of the mammalian brainstem and midbrain. The findings suggest that in these regions, GABAB receptors are involved in processes essential for proper auditory function, such as cochlear amplifier modulation, regulation of spontaneous activity, binaural and temporal information processing, and predictive coding. Since impaired GABAergic inhibition has been found to be associated with various forms of hearing loss, GABAB dysfunction could also play a role in some pathologies of the auditory system.
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Affiliation(s)
- Rostislav Tureček
- Department of Auditory Neuroscience, Institute of Experimental Medicine, Academy of Sciences of the Czech Republic, Prague, Czechia
| | - Adolf Melichar
- Department of Auditory Neuroscience, Institute of Experimental Medicine, Academy of Sciences of the Czech Republic, Prague, Czechia
- Second Faculty of Medicine, Charles University, Prague, Czechia
| | - Michaela Králíková
- Department of Auditory Neuroscience, Institute of Experimental Medicine, Academy of Sciences of the Czech Republic, Prague, Czechia
| | - Bohdana Hrušková
- Department of Auditory Neuroscience, Institute of Experimental Medicine, Academy of Sciences of the Czech Republic, Prague, Czechia
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7
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Gómez-Martínez M, Rincón H, Gómez-Álvarez M, Gómez-Nieto R, Saldaña E. The nuclei of the lateral lemniscus: unexpected players in the descending auditory pathway. Front Neuroanat 2023; 17:1242245. [PMID: 37621862 PMCID: PMC10445163 DOI: 10.3389/fnana.2023.1242245] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2023] [Accepted: 07/10/2023] [Indexed: 08/26/2023] Open
Abstract
Introduction In the mammalian auditory pathway, the nuclei of the lateral lemniscus (NLL) are thought to be exclusively involved in the bottom-up transmission of auditory information. However, our repeated observation of numerous NLL neurons labeled after injection of retrograde tracers into the superior olivary complex (SOC) led us to systematically investigate with retrograde tracers the descending projections from the NLL to the SOC of the rat. Methods We performed large injections of FluoroGold into the SOC to determine NLL contributions to descending projections, and focal injections of biotinylated dextran amine (BDA) to pinpoint the specific nuclei of the SOC innervated by each NLL. Results The SOC is innervated by thousands of neurons distributed across four nuclei or regions associated with the lateral lemniscus: the ipsilateral ventral and intermediate nuclei of the lateral lemniscus (VNLL and INLL); the medial paralemniscal region (PL) of both sides; and the ipsilateral semilunar nucleus (SLN), a previously unrecognized nucleus that wraps around the INLL dorsally, medially, and caudally and consists of small, flat neurons. In some experiments, at least 30% of neurons in the VNLL and INLL were retrogradely labeled. All nuclei of the SOC, except the medial and lateral superior olives, are innervated by abundant lemniscal neurons, and each SOC nucleus receives a unique combination of lemniscal inputs. The primary target of the projections from the VNLL is the ventral nucleus of the trapezoid body (VNTB), followed by the superior paraolivary nucleus (SPON), and the medial nucleus of the trapezoid body (MNTB). The INLL selectively innervates the VNTB. The PL innervates dorsal periolivary regions bilaterally. The SLN preferentially innervates the MNTB and may provide the first identified non-calyceal excitatory input to MNTB neurons. Discussion Our novel findings have strong implications for understanding acoustic information processing in the initial stages of the auditory pathway. Based on the proportion of lemniscal neurons involved in all the projections described, the NLL should be considered major players in the descending auditory pathway.
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Affiliation(s)
- Mario Gómez-Martínez
- Neuroscience Institute of Castilla y León, University of Salamanca, Salamanca, Spain
- Department of Cell Biology and Pathology, Medical School, University of Salamanca, Salamanca, Spain
- Institute of Biomedical Research of Salamanca, Salamanca, Spain
| | - Héctor Rincón
- Neuroscience Institute of Castilla y León, University of Salamanca, Salamanca, Spain
- Department of Cell Biology and Pathology, Medical School, University of Salamanca, Salamanca, Spain
- Institute of Biomedical Research of Salamanca, Salamanca, Spain
| | - Marcelo Gómez-Álvarez
- Neuroscience Institute of Castilla y León, University of Salamanca, Salamanca, Spain
- Department of Cell Biology and Pathology, Medical School, University of Salamanca, Salamanca, Spain
- Institute of Biomedical Research of Salamanca, Salamanca, Spain
| | - Ricardo Gómez-Nieto
- Neuroscience Institute of Castilla y León, University of Salamanca, Salamanca, Spain
- Department of Cell Biology and Pathology, Medical School, University of Salamanca, Salamanca, Spain
- Institute of Biomedical Research of Salamanca, Salamanca, Spain
| | - Enrique Saldaña
- Neuroscience Institute of Castilla y León, University of Salamanca, Salamanca, Spain
- Department of Cell Biology and Pathology, Medical School, University of Salamanca, Salamanca, Spain
- Institute of Biomedical Research of Salamanca, Salamanca, Spain
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Descending projections to the auditory midbrain: evolutionary considerations. J Comp Physiol A Neuroethol Sens Neural Behav Physiol 2023; 209:131-143. [PMID: 36323876 PMCID: PMC9898193 DOI: 10.1007/s00359-022-01588-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2022] [Revised: 10/12/2022] [Accepted: 10/14/2022] [Indexed: 11/06/2022]
Abstract
The mammalian inferior colliculus (IC) is massively innervated by multiple descending projection systems. In addition to a large projection from the auditory cortex (AC) primarily targeting the non-lemniscal portions of the IC, there are less well-characterized projections from non-auditory regions of the cortex, amygdala, posterior thalamus and the brachium of the IC. By comparison, the frog auditory midbrain, known as the torus semicircularis, is a large auditory integration center that also receives descending input, but primarily from the posterior thalamus and without a projection from a putative cortical homolog: the dorsal pallium. Although descending projections have been implicated in many types of behaviors, a unified understanding of their function has not yet emerged. Here, we take a comparative approach to understanding the various top-down modulators of the IC to gain insights into their functions. One key question that we identify is whether thalamotectal projections in mammals and amphibians are homologous and whether they interact with evolutionarily more newly derived projections from the cerebral cortex. We also consider the behavioral significance of these descending pathways, given anurans' ability to navigate complex acoustic landscapes without the benefit of a corticocollicular projection. Finally, we suggest experimental approaches to answer these questions.
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Beebe NL, Silveira MA, Goyer D, Noftz WA, Roberts MT, Schofield BR. Neurotransmitter phenotype and axonal projection patterns of VIP-expressing neurons in the inferior colliculus. J Chem Neuroanat 2022; 126:102189. [PMID: 36375740 PMCID: PMC9772258 DOI: 10.1016/j.jchemneu.2022.102189] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2022] [Revised: 11/09/2022] [Accepted: 11/09/2022] [Indexed: 11/13/2022]
Abstract
Neurons in the inferior colliculus (IC), the midbrain hub of the central auditory pathway, send ascending and descending projections to other auditory brain regions, as well as projections to other sensory and non-sensory brain regions. However, the axonal projection patterns of individual classes of IC neurons remain largely unknown. Vasoactive intestinal polypeptide (VIP) is a neuropeptide expressed by subsets of neurons in many brain regions. We recently identified a class of IC stellate neurons that we called VIP neurons because they are labeled by tdTomato (tdT) expression in VIP-IRES-Cre x Ai14 mice. Here, using fluorescence in situ hybridization, we found that tdT+ neurons in VIP-IRES-Cre x Ai14 mice express Vglut2, a marker of glutamatergic neurons, and VIP, suggesting that VIP neurons use both glutamatergic and VIPergic signaling to influence their postsynaptic targets. Next, using viral transfections with a Cre-dependent eGFP construct, we labeled the axonal projections of VIP neurons. As a group, VIP neurons project intrinsically, within the ipsilateral and contralateral IC, and extrinsically to all the major targets of the IC. Within the auditory system, VIP neurons sent axons and formed axonal boutons in higher centers, including the medial geniculate nucleus and the nucleus of the brachium of the IC. Less dense projections terminated in lower centers, including the nuclei of the lateral lemniscus, superior olivary complex, and dorsal cochlear nucleus. VIP neurons also project to several non-auditory brain regions, including the superior colliculus, periaqueductal gray, and cuneiform nucleus. The diversity of VIP projections compared to the homogeneity of VIP neuron intrinsic properties suggests that VIP neurons play a conserved role at the microcircuit level, likely involving neuromodulation through glutamatergic and VIPergic signaling, but support diverse functions at the systems level through their participation in different projection pathways.
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Affiliation(s)
- Nichole L Beebe
- Hearing Research Group, Department of Anatomy and Neurobiology, Northeast Ohio Medical University, Rootstown, OH, USA.
| | - Marina A Silveira
- Kresge Hearing Research Institute, Department of Otolaryngology-Head and Neck Surgery, University of Michigan, Ann Arbor, MI, USA.
| | - David Goyer
- Kresge Hearing Research Institute, Department of Otolaryngology-Head and Neck Surgery, University of Michigan, Ann Arbor, MI, USA.
| | - William A Noftz
- Hearing Research Group, Department of Anatomy and Neurobiology, Northeast Ohio Medical University, Rootstown, OH, USA.
| | - Michael T Roberts
- Kresge Hearing Research Institute, Department of Otolaryngology-Head and Neck Surgery, University of Michigan, Ann Arbor, MI, USA; Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI, USA.
| | - Brett R Schofield
- Hearing Research Group, Department of Anatomy and Neurobiology, Northeast Ohio Medical University, Rootstown, OH, USA.
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Electrical signaling in cochlear efferents is driven by an intrinsic neuronal oscillator. Proc Natl Acad Sci U S A 2022; 119:e2209565119. [PMID: 36306331 PMCID: PMC9636947 DOI: 10.1073/pnas.2209565119] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Efferent neurons are believed to play essential roles in maintaining auditory function. The lateral olivocochlear (LOC) neurons-which project from the brainstem to the inner ear, where they release multiple transmitters including peptides, catecholamines, and acetylcholine-are the most numerous yet least understood elements of efferent control of the cochlea. Using in vitro calcium imaging and patch-clamp recordings, we found that LOC neurons in juvenile and young adult mice exhibited extremely slow waves of activity (∼0.1 Hz). These seconds-long bursts of Na+ spikes were driven by an intrinsic oscillator dependent on L-type Ca2+ channels and were not observed in prehearing mice, suggesting an age-dependent mechanism underlying the intrinsic oscillator. Using optogenetic approaches, we identified both ascending (T-stellate cells of the cochlear nucleus) and descending (auditory cortex) sources of synaptic excitation, as well as the synaptic receptors used for such excitation. Additionally, we identified potent inhibition originating in the glycinergic medial nucleus of trapezoid body (MNTB). Conductance-clamp experiments revealed an unusual mechanism of electrical signaling in LOC neurons, in which synaptic excitation and inhibition served to switch on and off the intrinsically generated spike burst mechanism, allowing for prolonged periods of activity or silence controlled by brief synaptic events. Protracted bursts of action potentials may be essential for effective exocytosis of the diverse transmitters released by LOC fibers in the cochlea.
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11
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Pätz C, Console-Meyer L, Felmy F. Structural arrangement of auditory brainstem nuclei in the bats Phyllostomus discolor and Carollia perspicillata. J Comp Neurol 2022; 530:2762-2781. [PMID: 35703441 DOI: 10.1002/cne.25355] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2021] [Revised: 04/24/2022] [Accepted: 05/14/2022] [Indexed: 11/10/2022]
Abstract
The structure of the mammalian auditory brainstem is evolutionarily highly plastic, and distinct nuclei arrange in a species-dependent manner. Such anatomical variability is present in the superior olivary complex (SOC) and the nuclei of the lateral lemniscus (LL). Due to the structure-function relationship in the auditory brainstem, the identification of individual nuclei supports the understanding of sound processing. Here, we comparatively describe the nucleus arrangement and the expression of functional markers in the auditory brainstem of the two bat species Phyllostomus discolor and Carollia perspicillata. Using immunofluorescent labeling, we describe the arrangement and identity of the SOC and LL nuclei based on the expression of synaptic markers (vesicular glutamate transporter 1 and glycine transporter 2), calcium-binding proteins, as well as the voltage-gated ion channel subunits Kv1.1 and HCN1. The distribution of excitatory and inhibitory synaptic labeling appears similar between both species and matches with that of other mammals. The detection of calcium-binding proteins indicates species-dependent differences and deviations from other mammals. Kv1.1 and HCN1 show largely the same expression pattern in both species, which diverges from other mammals, indicating functional adaptations in the cellular physiology of bat neurons.
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Affiliation(s)
- Christina Pätz
- Institute of Zoology, University of Veterinary Medicine Hannover, Hannover, Germany
| | - Laura Console-Meyer
- Institute of Zoology, University of Veterinary Medicine Hannover, Hannover, Germany
| | - Felix Felmy
- Institute of Zoology, University of Veterinary Medicine Hannover, Hannover, Germany
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12
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Romero GE, Trussell LO. Central circuitry and function of the cochlear efferent systems. Hear Res 2022; 425:108516. [DOI: 10.1016/j.heares.2022.108516] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/14/2022] [Revised: 04/28/2022] [Accepted: 05/10/2022] [Indexed: 11/04/2022]
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13
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Cadenas LT, Cheng H, Weisz CJC. Synaptic plasticity of inhibitory synapses onto medial olivocochlear efferent neurons. J Physiol 2022; 600:2747-2763. [PMID: 35443073 PMCID: PMC9323901 DOI: 10.1113/jp282815] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2022] [Accepted: 04/04/2022] [Indexed: 11/18/2022] Open
Abstract
Abstract The descending auditory system modulates the ascending system at every level. The final descending, or efferent, stage comprises lateral olivocochlear and medial olivocochlear (MOC) neurons. MOC somata in the ventral brainstem project axons to the cochlea to synapse onto outer hair cells (OHC), inhibiting OHC‐mediated cochlear amplification. MOC suppression of OHC function is implicated in cochlear gain control with changing sound intensity, detection of salient stimuli, attention and protection against acoustic trauma. Thus, sound excites MOC neurons to provide negative feedback of the cochlea. Sound also inhibits MOC neurons via medial nucleus of the trapezoid body (MNTB) neurons. However, MNTB–MOC synapses exhibit short‐term depression, suggesting reduced MNTB–MOC inhibition during sustained stimuli. Further, due to high rates of both baseline and sound‐evoked activity in MNTB neurons in vivo, MNTB–MOC synapses may be tonically depressed. To probe this, we characterized short‐term plasticity of MNTB–MOC synapses in mouse brain slices. We mimicked in vivo‐like temperature and extracellular calcium conditions, and in vivo‐like activity patterns of fast synaptic activation rates, sustained activation and prior tonic activity. Synaptic depression was sensitive to extracellular calcium concentration and temperature. During rapid MNTB axon stimulation, postsynaptic currents in MOC neurons summated but with concurrent depression, resulting in smaller, sustained currents, suggesting tonic inhibition of MOC neurons during rapid circuit activity. Low levels of baseline MNTB activity did not significantly reduce responses to subsequent rapid activity that mimics sound stimulation, indicating that, in vivo, MNTB inhibition of MOC neurons persists despite tonic synaptic depression. Key points Inhibitory synapses from the medial nucleus of the trapezoid body (MNTB) onto medial olivocochlear (MOC) neurons exhibit short‐term plasticity that is sensitive to calcium and temperature, with enhanced synaptic depression occurring at higher calcium concentrations and at room temperature. High rates of background synaptic activity that mimic the upper limits of spontaneous MNTB activity cause tonic synaptic depression of MNTB–MOC synapses that limits further synaptic inhibition. High rates of activity at MNTB–MOC synapses cause synaptic summation with concurrent depression to yield a response with an initial large amplitude that decays to a tonic inhibition.
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Affiliation(s)
- Lester Torres Cadenas
- Section on Neuronal Circuitry, National Institute on Deafness and Other Communication Disorders, NIH, Bethesda, MD, 20892, USA
| | - Hui Cheng
- Bioinformatics and Biostatistics Collaboration Core, National Institute on Deafness and Other Communication Disorders, NIH, Bethesda, MD, 20892, USA
| | - Catherine J C Weisz
- Section on Neuronal Circuitry, National Institute on Deafness and Other Communication Disorders, NIH, Bethesda, MD, 20892, USA
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14
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Balmer TS, Trussell LO. Descending Axonal Projections from the Inferior Colliculus Target Nearly All Excitatory and Inhibitory Cell Types of the Dorsal Cochlear Nucleus. J Neurosci 2022; 42:3381-3393. [PMID: 35273085 PMCID: PMC9034789 DOI: 10.1523/jneurosci.1190-21.2022] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2021] [Revised: 02/24/2022] [Accepted: 02/25/2022] [Indexed: 11/21/2022] Open
Abstract
The dorsal cochlear nucleus (DCN) integrates auditory nerve input with nonauditory sensory signals and is proposed to function in sound source localization and suppression of self-generated sounds. The DCN also integrates activity from descending auditory pathways, including a particularly large feedback projection from the inferior colliculus (IC), the main ascending target of the DCN. Understanding how these descending feedback signals are integrated into the DCN circuit and what role they play in hearing requires knowing the targeted DCN cell types and their postsynaptic responses. In order to explore these questions, neurons in the DCN that received descending synaptic input from the IC were labeled with a trans-synaptic viral approach in male and female mice, which allowed them to be targeted for whole-cell recording in acute brain slices. We tested their synaptic responses to optogenetic activation of the descending IC projection. Every cell type in the granule cell domain received monosynaptic, glutamatergic input from the IC, indicating that this region, considered an integrator of nonauditory sensory inputs, processes auditory input as well and may have complex and underappreciated roles in hearing. Additionally, we found that DCN cell types outside the granule cell regions also receive descending IC signals, including the principal projection neurons, as well as the neurons that inhibit them, leading to a circuit that may sharpen tuning through feedback excitation and lateral inhibition.SIGNIFICANCE STATEMENT Auditory processing starts in the cochlea and ascends through the dorsal cochlear nucleus (DCN) to the inferior colliculus (IC) and beyond. Here, we investigated the feedback projection from IC to DCN, whose synaptic targets and roles in auditory processing are unclear. We found that all cell types in the granule cell regions, which process multisensory feedback, also process this descending auditory feedback. Surprisingly, all except one cell type in the entire DCN receive IC input. The IC-DCN projection may therefore modulate the multisensory pathway as well as sharpen tuning and gate auditory signals that are sent to downstream areas. This excitatory feedback loop from DCN to IC and back to DCN could underlie hyperexcitability in DCN, widely considered an etiology of tinnitus.
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Affiliation(s)
- Timothy S Balmer
- Vollum Institute and Oregon Hearing Research Center, Oregon Health & Science University, Portland, Oregon 97239
| | - Laurence O Trussell
- Vollum Institute and Oregon Hearing Research Center, Oregon Health & Science University, Portland, Oregon 97239
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15
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Mansour Y, Kulesza RJ. The Untouchable Ventral Nucleus of the Trapezoid Body: Preservation of a Nucleus in an Animal Model of Autism Spectrum Disorder. Front Integr Neurosci 2021; 15:730439. [PMID: 34658803 PMCID: PMC8511769 DOI: 10.3389/fnint.2021.730439] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2021] [Accepted: 09/08/2021] [Indexed: 12/23/2022] Open
Abstract
Autism spectrum disorder (ASD) is a neurodevelopmental condition characterized by repetitive behaviors, poor social skills, and difficulties with communication and hearing. The hearing deficits in ASD range from deafness to extreme sensitivity to routine environmental sounds. Previous research from our lab has shown drastic hypoplasia in the superior olivary complex (SOC) in both human cases of ASD and in an animal model of autism. However, in our study of the human SOC, we failed to find any changes in the total number of neurons in the ventral nucleus of the trapezoid body (VNTB) or any changes in cell body size or shape. Similarly, in animals prenatally exposed to the antiepileptic valproic acid (VPA), we failed to find any changes in the total number, size or shape of VNTB neurons. Based on these findings, we hypothesized that the neurotransmitter profiles, ascending and descending axonal projections of the VNTB are also preserved in these neurodevelopmental conditions. We investigated this hypothesis using a combination of immunohistochemistry and retrograde tract tracing. We found no difference between control and VPA-exposed animals in the number of VNTB neurons immunoreactive for choline acetyltransferase (ChAT). Additionally, we investigated the ascending projections from the VNTB to both the central nucleus of the inferior colliculus (CNIC) and medial geniculate (MG) and descending projections to the cochlea. Our results indicate no significant differences in the ascending and descending projections from the VNTB between control and VPA-exposed animals despite drastic changes in these projections from surrounding nuclei. These findings provide evidence that certain neuronal populations and circuits may be protected against the effects of neurodevelopmental disorders.
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Affiliation(s)
- Yusra Mansour
- Department of Otolaryngology, Henry Ford Macomb Hospital, Clinton Township, MI, United States.,Department of Anatomy, Lake Erie College of Osteopathic Medicine, Erie, PA, United States
| | - Randy J Kulesza
- Department of Anatomy, Lake Erie College of Osteopathic Medicine, Erie, PA, United States
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16
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Excitatory cholecystokinin neurons of the midbrain integrate diverse temporal responses and drive auditory thalamic subdomains. Proc Natl Acad Sci U S A 2021; 118:2007724118. [PMID: 33658359 PMCID: PMC7958253 DOI: 10.1073/pnas.2007724118] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Our ability to identify sounds and understand communication signals depends upon our brains’ capacity to combine information about diverse sound features, including temporal patterns. The central nucleus of the inferior colliculus (ICC) performs an initial stage of this integration, but a circuit-based understanding of these processes has been hampered by difficulties in separating clearly defined functional cell types. Here we identify and characterize a major excitatory projection neuron of the ICC. These neurons show uniform intrinsic firing patterns and tuning to frequency, but strikingly diverse temporal responses to sound. Our results suggest that diversity in temporal coding is represented even within a single cell class and is likely primarily driven by differences in circuit connectivity. The central nucleus of the inferior colliculus (ICC) integrates information about different features of sound and then distributes this information to thalamocortical circuits. However, the lack of clear definitions of circuit elements in the ICC has limited our understanding of the nature of these circuit transformations. Here, we combine virus-based genetic access with electrophysiological and optogenetic approaches to identify a large family of excitatory, cholecystokinin-expressing thalamic projection neurons in the ICC of the Mongolian gerbil. We show that these neurons form a distinct cell type, displaying uniform morphology and intrinsic firing features, and provide powerful, spatially restricted excitation exclusively to the ventral auditory thalamus. In vivo, these neurons consistently exhibit V-shaped receptive field properties but strikingly diverse temporal responses to sound. Our results indicate that temporal response diversity is maintained within this population of otherwise uniform cells in the ICC and then relayed to cortex through spatially restricted thalamic subdomains.
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17
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Romero GE, Trussell LO. Distinct forms of synaptic plasticity during ascending vs descending control of medial olivocochlear efferent neurons. eLife 2021; 10:66396. [PMID: 34250904 PMCID: PMC8321555 DOI: 10.7554/elife.66396] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2021] [Accepted: 07/09/2021] [Indexed: 12/14/2022] Open
Abstract
Activity in each brain region is shaped by the convergence of ascending and descending axonal pathways, and the balance and characteristics of these determine the neural output. The medial olivocochlear (MOC) efferent system is part of a reflex arc that critically controls auditory sensitivity. Multiple central pathways contact MOC neurons, raising the question of how a reflex arc could be engaged by diverse inputs. We examined functional properties of synapses onto brainstem MOC neurons from ascending (ventral cochlear nucleus, VCN) and descending (inferior colliculus, IC) sources in mice using an optogenetic approach. We found that these pathways exhibited opposing forms of short-term plasticity, with the VCN input showing depression and the IC input showing marked facilitation. By using a conductance-clamp approach, we found that combinations of facilitating and depressing inputs enabled firing of MOC neurons over a surprisingly wide dynamic range, suggesting an essential role for descending signaling to a brainstem nucleus.
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Affiliation(s)
- Gabriel E Romero
- Physiology & Pharmacology Graduate Program, Oregon Health & Science University, Portland, United States
| | - Laurence O Trussell
- Oregon Hearing Research Center and Vollum Institute, Oregon Health & Science University, Portland, United States
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18
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Beebe NL, Schofield BR. Cholinergic boutons are closely associated with excitatory cells and four subtypes of inhibitory cells in the inferior colliculus. J Chem Neuroanat 2021; 116:101998. [PMID: 34186203 DOI: 10.1016/j.jchemneu.2021.101998] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2021] [Revised: 06/23/2021] [Accepted: 06/24/2021] [Indexed: 01/23/2023]
Abstract
Acetylcholine (ACh) is a neuromodulator that has been implicated in multiple roles across the brain, including the central auditory system, where it sets neuronal excitability and gain and affects plasticity. In the cerebral cortex, subtypes of GABAergic interneurons are modulated by ACh in a subtype-specific manner. Subtypes of GABAergic neurons have also begun to be described in the inferior colliculus (IC), a midbrain hub of the auditory system. Here, we used male and female mice (Mus musculus) that express fluorescent protein in cholinergic cells, axons, and boutons to look at the association between ACh and four subtypes of GABAergic IC cells that differ in their associations with extracellular markers, their soma sizes, and their distribution within the IC. We found that most IC cells, including excitatory and inhibitory cells, have cholinergic boutons closely associated with their somas and proximal dendrites. We also found that similar proportions of each of four subtypes of GABAergic cells are closely associated with cholinergic boutons. Whether the different types of GABAergic cells in the IC are differentially regulated remains unclear, as the response of cells to ACh is dependent on which types of ACh receptors are present. Additionally, this study confirms the presence of these four subtypes of GABAergic cells in the mouse IC, as they had previously been identified only in guinea pigs. These results suggest that cholinergic projections to the IC modulate auditory processing via direct effects on a multitude of inhibitory circuits.
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Affiliation(s)
- Nichole L Beebe
- Hearing Research Focus Group, Northeast Ohio Medical University, Rootstown, OH, USA; Brain Health Research Institute, Kent State University, Kent, OH, USA.
| | - Brett R Schofield
- Hearing Research Focus Group, Northeast Ohio Medical University, Rootstown, OH, USA; Brain Health Research Institute, Kent State University, Kent, OH, USA.
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19
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Ghosh S, Stansak K, Walters BJ. Cannabinoid Signaling in Auditory Function and Development. Front Mol Neurosci 2021; 14:678510. [PMID: 34079440 PMCID: PMC8165240 DOI: 10.3389/fnmol.2021.678510] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2021] [Accepted: 04/15/2021] [Indexed: 12/20/2022] Open
Abstract
Plants of the genus Cannabis have been used by humans for millennia for a variety of purposes. Perhaps most notable is the use of certain Cannabis strains for their psychoactive effects. More recently, several biologically active molecules within the plants of these Cannabis strains, called phytocannabinoids or simply cannabinoids, have been identified. Furthermore, within human cells, endogenous cannabinoids, or endocannabinoids, as well as the receptors and secondary messengers that give rise to their neuromodulatory effects, have also been characterized. This endocannabinoid system (ECS) is composed of two primary ligands-anandamide and 2-arachidonyl glycerol; two primary receptors-cannabinoid receptors 1 and 2; and several enzymes involved in biosynthesis and degradation of endocannabinoid ligands including diacylglycerol lipase (DAGL) and monoacylglycerol lipase (MAGL). Here we briefly summarize cannabinoid signaling and review what has been discerned to date with regard to cannabinoid signaling in the auditory system and its roles in normal physiological function as well as pathological conditions. While much has been uncovered regarding cannabinoid signaling in the central nervous system, less attention has been paid to the auditory system specifically. Still, evidence is emerging to suggest that cannabinoid signaling is critical for the development, maturation, function, and survival of cochlear hair cells (HCs) and spiral ganglion neurons (SGNs). Furthermore, cannabinoid signaling can have profound effects on synaptic connectivity in CNS structures related to auditory processing. While clinical cases demonstrate that endogenous and exogenous cannabinoids impact auditory function, this review highlights several areas, such as SGN development, where more research is warranted.
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Affiliation(s)
- Sumana Ghosh
- Department of Neurobiology and Anatomical Sciences, University of Mississippi Medical Center, Jackson, MS, United States
| | - Kendra Stansak
- Department of Neurobiology and Anatomical Sciences, University of Mississippi Medical Center, Jackson, MS, United States
| | - Bradley J Walters
- Department of Neurobiology and Anatomical Sciences, University of Mississippi Medical Center, Jackson, MS, United States.,Department of Otolaryngology-Head and Neck Surgery, University of Mississippi Medical Center, Jackson, MS, United States
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20
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Lazarini-Lopes W, Do Val-da Silva RA, da Silva-Júnior RMP, Cunha AOS, Garcia-Cairasco N. Cannabinoids in Audiogenic Seizures: From Neuronal Networks to Future Perspectives for Epilepsy Treatment. Front Behav Neurosci 2021; 15:611902. [PMID: 33643007 PMCID: PMC7904685 DOI: 10.3389/fnbeh.2021.611902] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2020] [Accepted: 01/06/2021] [Indexed: 12/17/2022] Open
Abstract
Cannabinoids and Cannabis-derived compounds have been receiving especial attention in the epilepsy research scenario. Pharmacological modulation of endocannabinoid system's components, like cannabinoid type 1 receptors (CB1R) and their bindings, are associated with seizures in preclinical models. CB1R expression and functionality were altered in humans and preclinical models of seizures. Additionally, Cannabis-derived compounds, like cannabidiol (CBD), present anticonvulsant activity in humans and in a great variety of animal models. Audiogenic seizures (AS) are induced in genetically susceptible animals by high-intensity sound stimulation. Audiogenic strains, like the Genetically Epilepsy Prone Rats, Wistar Audiogenic Rats, and Krushinsky-Molodkina, are useful tools to study epilepsy. In audiogenic susceptible animals, acute acoustic stimulation induces brainstem-dependent wild running and tonic-clonic seizures. However, during the chronic protocol of AS, the audiogenic kindling (AuK), limbic and cortical structures are recruited, and the initially brainstem-dependent seizures give rise to limbic seizures. The present study reviewed the effects of pharmacological modulation of the endocannabinoid system in audiogenic seizure susceptibility and expression. The effects of Cannabis-derived compounds in audiogenic seizures were also reviewed, with especial attention to CBD. CB1R activation, as well Cannabis-derived compounds, induced anticonvulsant effects against audiogenic seizures, but the effects of cannabinoids modulation and Cannabis-derived compounds still need to be verified in chronic audiogenic seizures. The effects of cannabinoids and Cannabis-derived compounds should be further investigated not only in audiogenic seizures, but also in epilepsy related comorbidities present in audiogenic strains, like anxiety, and depression.
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Affiliation(s)
- Willian Lazarini-Lopes
- Neuroscience and Behavioral Sciences Department, Ribeirão Preto School of Medicine, University of São Paulo, São Paulo, Brazil
- Neurophysiology and Experimental Neuroethology Laboratory (LNNE), Physiology Department, Ribeirão Preto School of Medicine, University of São Paulo, São Paulo, Brazil
| | - Raquel A. Do Val-da Silva
- Neuroscience and Behavioral Sciences Department, Ribeirão Preto School of Medicine, University of São Paulo, São Paulo, Brazil
| | - Rui M. P. da Silva-Júnior
- Neurophysiology and Experimental Neuroethology Laboratory (LNNE), Physiology Department, Ribeirão Preto School of Medicine, University of São Paulo, São Paulo, Brazil
| | - Alexandra O. S. Cunha
- Physiology Department, Ribeirão Preto School of Medicine, University of São Paulo, São Paulo, Brazil
| | - Norberto Garcia-Cairasco
- Neuroscience and Behavioral Sciences Department, Ribeirão Preto School of Medicine, University of São Paulo, São Paulo, Brazil
- Neurophysiology and Experimental Neuroethology Laboratory (LNNE), Physiology Department, Ribeirão Preto School of Medicine, University of São Paulo, São Paulo, Brazil
- Physiology Department, Ribeirão Preto School of Medicine, University of São Paulo, São Paulo, Brazil
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21
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Badea A, Schmalzigaug R, Kim W, Bonner P, Ahmed U, Johnson GA, Cofer G, Foster M, Anderson RJ, Badea C, Premont RT. Microcephaly with altered cortical layering in GIT1 deficiency revealed by quantitative neuroimaging. Magn Reson Imaging 2021; 76:26-38. [PMID: 33010377 PMCID: PMC7802083 DOI: 10.1016/j.mri.2020.09.023] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2020] [Revised: 09/25/2020] [Accepted: 09/25/2020] [Indexed: 01/06/2023]
Abstract
G Protein-Coupled Receptor Kinase-Interacting Protein-1 (GIT1) regulates neuronal functions, including cell and axon migration and synapse formation and maintenance, and GIT1 knockout (KO) mice exhibit learning and memory deficits. We noted that male and female GIT1-KO mice exhibit neuroimaging phenotypes including microcephaly, and altered cortical layering, with a decrease in neuron density in cortical layer V. Micro-CT and magnetic resonance microscopy (MRM) were used to identify morphometric phenotypes for the skulls and throughout the GIT1-KO brains. High field MRM of actively-stained mouse brains from GIT1-KO and wild type (WT) controls (n = 6 per group) allowed segmenting 37 regions, based on co-registration to the Waxholm Space atlas. Overall brain size in GIT1-KO mice was ~32% smaller compared to WT controls. After correcting for brain size, several regions were significantly different in GIT1-KO mice relative to WT, including the gray matter of the ventral thalamic nuclei and the rest of the thalamus, the inferior colliculus, and pontine nuclei. GIT1-KO mice had reduced volume of white matter tracts, most notably in the anterior commissure (~26% smaller), but also in the cerebral peduncle, fornix, and spinal trigeminal tract. On the other hand, the basal ganglia appeared enlarged in GIT1-KO mice, including the globus pallidus, caudate putamen, and particularly the accumbens - supporting a possible vulnerability to addiction. Volume based morphometry based on high-resolution MRM (21.5 μm isotropic voxels) was effective in detecting overall, and local differences in brain volumes in GIT1-KO mice, including in white matter tracts. The reduced relative volume of specific brain regions suggests a critical, but not uniform, role for GIT1 in brain development, conducive to brain microcephaly, and aberrant connectivity.
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Affiliation(s)
- Alexandra Badea
- Department of Radiology, Duke University Medical Center, Durham, NC 27710, United States of America; Department of Neurology, Duke University Medical Center, Durham, NC 27710, United States of America; Departments of Biomedical Engineering, Duke University Medical Center, Durham, NC 27710, United States of America; Brain Imaging and Analysis Center, Duke University Medical Center, Durham, NC 27710, United States of America.
| | - Robert Schmalzigaug
- Department of Medicine, Duke University Medical Center, Durham, NC 27710, United States of America
| | - Woojoo Kim
- Department of Medicine, Duke University Medical Center, Durham, NC 27710, United States of America
| | - Pamela Bonner
- Department of Medicine, Duke University Medical Center, Durham, NC 27710, United States of America
| | - Umer Ahmed
- Department of Medicine, Duke University Medical Center, Durham, NC 27710, United States of America
| | - G Allan Johnson
- Department of Radiology, Duke University Medical Center, Durham, NC 27710, United States of America; Departments of Biomedical Engineering, Duke University Medical Center, Durham, NC 27710, United States of America
| | - Gary Cofer
- Department of Radiology, Duke University Medical Center, Durham, NC 27710, United States of America
| | - Mark Foster
- Department of Radiology, Duke University Medical Center, Durham, NC 27710, United States of America
| | - Robert J Anderson
- Department of Radiology, Duke University Medical Center, Durham, NC 27710, United States of America
| | - Cristian Badea
- Department of Radiology, Duke University Medical Center, Durham, NC 27710, United States of America; Departments of Biomedical Engineering, Duke University Medical Center, Durham, NC 27710, United States of America
| | - Richard T Premont
- Department of Medicine, Duke University Medical Center, Durham, NC 27710, United States of America.
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22
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Asilador A, Llano DA. Top-Down Inference in the Auditory System: Potential Roles for Corticofugal Projections. Front Neural Circuits 2021; 14:615259. [PMID: 33551756 PMCID: PMC7862336 DOI: 10.3389/fncir.2020.615259] [Citation(s) in RCA: 28] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2020] [Accepted: 12/17/2020] [Indexed: 01/28/2023] Open
Abstract
It has become widely accepted that humans use contextual information to infer the meaning of ambiguous acoustic signals. In speech, for example, high-level semantic, syntactic, or lexical information shape our understanding of a phoneme buried in noise. Most current theories to explain this phenomenon rely on hierarchical predictive coding models involving a set of Bayesian priors emanating from high-level brain regions (e.g., prefrontal cortex) that are used to influence processing at lower-levels of the cortical sensory hierarchy (e.g., auditory cortex). As such, virtually all proposed models to explain top-down facilitation are focused on intracortical connections, and consequently, subcortical nuclei have scarcely been discussed in this context. However, subcortical auditory nuclei receive massive, heterogeneous, and cascading descending projections at every level of the sensory hierarchy, and activation of these systems has been shown to improve speech recognition. It is not yet clear whether or how top-down modulation to resolve ambiguous sounds calls upon these corticofugal projections. Here, we review the literature on top-down modulation in the auditory system, primarily focused on humans and cortical imaging/recording methods, and attempt to relate these findings to a growing animal literature, which has primarily been focused on corticofugal projections. We argue that corticofugal pathways contain the requisite circuitry to implement predictive coding mechanisms to facilitate perception of complex sounds and that top-down modulation at early (i.e., subcortical) stages of processing complement modulation at later (i.e., cortical) stages of processing. Finally, we suggest experimental approaches for future studies on this topic.
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Affiliation(s)
- Alexander Asilador
- Neuroscience Program, The University of Illinois at Urbana-Champaign, Champaign, IL, United States
- Beckman Institute for Advanced Science and Technology, Urbana, IL, United States
| | - Daniel A. Llano
- Neuroscience Program, The University of Illinois at Urbana-Champaign, Champaign, IL, United States
- Beckman Institute for Advanced Science and Technology, Urbana, IL, United States
- Molecular and Integrative Physiology, The University of Illinois at Urbana-Champaign, Champaign, IL, United States
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23
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Henschke JU, Pakan JM. Disynaptic cerebrocerebellar pathways originating from multiple functionally distinct cortical areas. eLife 2020; 9:59148. [PMID: 32795386 PMCID: PMC7428308 DOI: 10.7554/elife.59148] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2020] [Accepted: 07/28/2020] [Indexed: 12/31/2022] Open
Abstract
The cerebral cortex and cerebellum both play important roles in sensorimotor processing, however, precise connections between these major brain structures remain elusive. Using anterograde mono-trans-synaptic tracing, we elucidate cerebrocerebellar pathways originating from primary motor, sensory, and association cortex. We confirm a highly organized topography of corticopontine projections in mice; however, we found no corticopontine projections originating from primary auditory cortex and detail several potential extra-pontine cerebrocerebellar pathways. The cerebellar hemispheres were the major target of resulting disynaptic mossy fiber terminals, but we also found at least sparse cerebrocerebellar projections to every lobule of the cerebellum. Notably, projections originating from association cortex resulted in less laterality than primary sensory/motor cortices. Within molecularly defined cerebellar modules we found spatial overlap of mossy fiber terminals, originating from functionally distinct cortical areas, within crus I, paraflocculus, and vermal regions IV/V and VI - highlighting these regions as potential hubs for multimodal cortical influence.
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Affiliation(s)
- Julia U Henschke
- Institute of Cognitive Neurology and Dementia Research, Otto-von-Guericke-University, Magdeburg, Germany.,German Centre for Neurodegenerative Diseases, Magdeburg, Germany
| | - Janelle Mp Pakan
- Institute of Cognitive Neurology and Dementia Research, Otto-von-Guericke-University, Magdeburg, Germany.,German Centre for Neurodegenerative Diseases, Magdeburg, Germany.,Center for Behavioral Brain Sciences, Universitätsplatz, Magdeburg, Germany
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24
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Circuit Mechanisms Underlying the Segregation and Integration of Parallel Processing Streams in the Inferior Colliculus. J Neurosci 2020; 40:6328-6344. [PMID: 32665405 DOI: 10.1523/jneurosci.0646-20.2020] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2020] [Revised: 06/28/2020] [Accepted: 07/04/2020] [Indexed: 11/21/2022] Open
Abstract
The lateral cortex of the inferior colliculus (LCIC) forms a nexus between diverse multisensory, motor, and neuromodulatory streams. Like other integration hubs, it contains repeated neurochemical motifs with distinct inputs: GABA-rich modules are innervated by somatosensory structures, while auditory inputs to the LCIC target the surrounding extramodular matrix. To investigate potential mechanisms of convergence between these input streams, we used laser photostimulation circuit mapping to interrogate local LCIC circuits in adult mice of both sexes and found that input patterns are highly dependent on cell type (GABAergic/non-GABAergic) and location (module/matrix). At the circuit level, these inputs yield a directional flow of local information, primarily from the matrix to the modules. Further, the two compartments were found to project to distinct targets in the midbrain and thalamus. These data show that, while connectional modularity in the LCIC gives rise to segregated input-output channels, local circuits provide the architecture for integration between these two streams.SIGNIFICANCE STATEMENT Modularity is a widespread motif across the brain involving the segregation of structures into discrete subregions based on dichotomies in neurochemical expression or connectivity. The inferior colliculus is one such modular structure, containing auditory-recipient matrix regions and GABA-rich modules that are innervated by somatosensory inputs. While modularity suggests segregation of processing streams, here we show that local circuits in the inferior colliculus connect the module and matrix regions, providing an avenue for integration of information across compartments.
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Torres Cadenas L, Fischl MJ, Weisz CJC. Synaptic Inhibition of Medial Olivocochlear Efferent Neurons by Neurons of the Medial Nucleus of the Trapezoid Body. J Neurosci 2020; 40:509-525. [PMID: 31719165 PMCID: PMC6961997 DOI: 10.1523/jneurosci.1288-19.2019] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2019] [Revised: 10/29/2019] [Accepted: 11/04/2019] [Indexed: 02/08/2023] Open
Abstract
Medial olivocochlear (MOC) efferent neurons in the brainstem comprise the final stage of descending control of the mammalian peripheral auditory system through axon projections to the cochlea. MOC activity adjusts cochlear gain and frequency tuning, and protects the ear from acoustic trauma. The neuronal pathways that activate and modulate the MOC somata in the brainstem to drive these cochlear effects are poorly understood. Evidence suggests that MOC neurons are primarily excited by sound stimuli in a three-neuron activation loop from the auditory nerve via an intermediate neuron in the cochlear nucleus. Anatomical studies suggest that MOC neurons receive diverse synaptic inputs, but the functional effect of additional synaptic influences on MOC neuron responses is unknown. Here we use patch-clamp electrophysiological recordings from identified MOC neurons in brainstem slices from mice of either sex to demonstrate that in addition to excitatory glutamatergic synapses, MOC neurons receive inhibitory GABAergic and glycinergic synaptic inputs. These synapses are activated by electrical stimulation of axons near the medial nucleus of the trapezoid body (MNTB). Focal glutamate uncaging confirms MNTB neurons as a source of inhibitory synapses onto MOC neurons. MNTB neurons inhibit MOC action potentials, but this effect depresses with repeat activation. This work identifies a new pathway of connectivity between brainstem auditory neurons and indicates that MOC neurons are both excited and inhibited by sound stimuli received at the same ear. The pathway depression suggests that the effect of MNTB inhibition of MOC neurons diminishes over the course of a sustained sound.SIGNIFICANCE STATEMENT Medial olivocochlear (MOC) neurons are the final stage of descending control of the mammalian auditory system and exert influence on cochlear mechanics to modulate perception of acoustic stimuli. The brainstem pathways that drive MOC function are poorly understood. Here we show for the first time that MOC neurons are inhibited by neurons of the MNTB, which may suppress the effects of MOC activity on the cochlea.
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Affiliation(s)
- Lester Torres Cadenas
- Section on Neuronal Circuitry, National Institute on Deafness and Other Communication Disorders, NIH, Bethesda, Maryland 20892
| | - Matthew J Fischl
- Section on Neuronal Circuitry, National Institute on Deafness and Other Communication Disorders, NIH, Bethesda, Maryland 20892
| | - Catherine J C Weisz
- Section on Neuronal Circuitry, National Institute on Deafness and Other Communication Disorders, NIH, Bethesda, Maryland 20892
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Waxholm Space atlas of the rat brain auditory system: Three-dimensional delineations based on structural and diffusion tensor magnetic resonance imaging. Neuroimage 2019; 199:38-56. [DOI: 10.1016/j.neuroimage.2019.05.016] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2019] [Revised: 05/01/2019] [Accepted: 05/06/2019] [Indexed: 12/14/2022] Open
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Yin TC, Smith PH, Joris PX. Neural Mechanisms of Binaural Processing in the Auditory Brainstem. Compr Physiol 2019; 9:1503-1575. [DOI: 10.1002/cphy.c180036] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
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Neurons, Connections, and Microcircuits of the Inferior Colliculus. THE MAMMALIAN AUDITORY PATHWAYS 2018. [DOI: 10.1007/978-3-319-71798-2_6] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
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de Oliveira RP, Nagaishi KY, Barbosa Silva RC. Atypical antipsychotic clozapine reversed deficit on prepulse inhibition of the acoustic startle reflex produced by microinjection of DOI into the inferior colliculus in rats. Behav Brain Res 2017; 325:72-78. [DOI: 10.1016/j.bbr.2017.01.053] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2016] [Revised: 01/20/2017] [Accepted: 01/25/2017] [Indexed: 01/23/2023]
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Suthakar K, Ryugo DK. Descending projections from the inferior colliculus to medial olivocochlear efferents: Mice with normal hearing, early onset hearing loss, and congenital deafness. Hear Res 2017; 343:34-49. [DOI: 10.1016/j.heares.2016.06.014] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/12/2016] [Revised: 06/20/2016] [Accepted: 06/24/2016] [Indexed: 11/24/2022]
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Milinkeviciute G, Muniak MA, Ryugo DK. Descending projections from the inferior colliculus to the dorsal cochlear nucleus are excitatory. J Comp Neurol 2016; 525:773-793. [PMID: 27513294 DOI: 10.1002/cne.24095] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2016] [Revised: 06/10/2016] [Accepted: 08/08/2016] [Indexed: 12/19/2022]
Abstract
Ascending projections of the dorsal cochlear nucleus (DCN) target primarily the contralateral inferior colliculus (IC). In turn, the IC sends bilateral descending projections back to the DCN. We sought to determine the nature of these descending axons in order to infer circuit mechanisms of signal processing at one of the earliest stages of the central auditory pathway. An anterograde tracer was injected in the IC of CBA/Ca mice to reveal terminal characteristics of the descending axons. Retrograde tracer deposits were made in the DCN of CBA/Ca and transgenic GAD67-EGFP mice to investigate the cells giving rise to these projections. A multiunit best frequency was determined for each injection site. Brains were processed by using standard histologic methods for visualization and examined by fluorescent, brightfield, and electron microscopy. Descending projections from the IC were inferred to be excitatory because the cell bodies of retrogradely labeled neurons did not colabel with EGFP expression in neurons of GAD67-EGFP mice. Furthermore, additional experiments yielded no glycinergic or cholinergic positive cells in the IC, and descending projections to the DCN were colabeled with antibodies against VGluT2, a glutamate transporter. Anterogradely labeled endings in the DCN formed asymmetric postsynaptic densities, a feature of excitatory neurotransmission. These descending projections to the DCN from the IC were topographic and suggest a feedback pathway that could underlie a frequency-specific enhancement of some acoustic signals and suppression of others. The involvement of this IC-DCN circuit is especially noteworthy when considering the gating of ascending signal streams for auditory processing. J. Comp. Neurol. 525:773-793, 2017. © 2016 Wiley Periodicals, Inc.
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Affiliation(s)
- Giedre Milinkeviciute
- Hearing Research, Garvan Institute of Medical Research, Sydney, New South Wales, 2010, Australia.,School of Medical Sciences, Faculty of Medicine, University of New South Wales, Sydney, New South Wales, 2052, Australia
| | - Michael A Muniak
- Hearing Research, Garvan Institute of Medical Research, Sydney, New South Wales, 2010, Australia
| | - David K Ryugo
- Hearing Research, Garvan Institute of Medical Research, Sydney, New South Wales, 2010, Australia.,School of Medical Sciences, Faculty of Medicine, University of New South Wales, Sydney, New South Wales, 2052, Australia.,Department of Otolaryngology, Head, Neck and Skull Base Surgery, St. Vincent's Hospital, Sydney, New South Wales, 2010, Australia
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Vetter DE. The mammalian olivocochlear system--a legacy of non-cerebellar research in the Mugnaini lab. THE CEREBELLUM 2016; 14:557-69. [PMID: 25592068 DOI: 10.1007/s12311-014-0637-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Although the major emphasis of Enrico Mugnaini's research has been on investigations of the cerebellum, a significant amount of work over a relatively short span of time was also done in his lab on a number of other brain systems. These centered on sensory systems. One of these extra-cerebellar systems that he embraced was the auditory system. Portions of the cochlear nucleus, the first synaptic relay station along the central auditory pathways, possess a cerebellar-like circuitry and neurochemistry, and this no doubt lured Enrico into the auditory field. As new tools became available to pursue neuroanatomical research in general, which included a novel antibody to glutamic acid decarboxylase (GAD), Enrico's lab soon branched out into investigating many other brain structures beyond the cerebellum, with an overall goal of producing a map illustrating GAD expression in the brain. In collaboration with long-term colleagues, one of these many non-cerebellar regions he took an interest in was an efferent pathway originating in the superior olive and projecting to the cochlea, the peripheral end organ for hearing. There was a need for a more complete neurochemical map of this olivocochlear efferent system, and armed with new antibodies and well-established tract tracing tools, together we set out to further explore this system. This short review describes the work done with Enrico on the olivocochlear system of rodents, and also continues the story beyond Enrico's lab to reveal how the work done in his lab fits into the larger scheme of current, ongoing research into the olivocochlear system.
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Affiliation(s)
- Douglas E Vetter
- Department of Neurobiology and Anatomical Sciences, University of Mississippi Medical Center, Jackson, MS, 39216, USA.
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Saldaña E. All the way from the cortex: a review of auditory corticosubcollicular pathways. THE CEREBELLUM 2016; 14:584-96. [PMID: 26142291 DOI: 10.1007/s12311-015-0694-4] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Enrico Mugnaini has devoted part of his long and fruitful neuroscientific career to investigating the structural similarities between the cerebellar cortex and one of the first relay stations of the mammalian auditory pathway: the dorsal cochlear nucleus. The hypothesis of the cerebellar-like nature of the superficial layers of the dorsal cochlear nucleus received definitive support with the discovery and extensive characterization in his laboratory of unipolar brush cells, a neuron type unique to certain regions of the cerebellar cortex and to the granule cell domains of the cochlear nuclei. Paradoxically, a different line of research carried out in his laboratory revealed that, unlike the mammalian cerebellar cortex, the dorsal cochlear nucleus receives direct projections from the cerebral cortex, a fact that constitutes one of the main differences between the cerebellum and the dorsal cochlear nucleus. In an article published in 1995, Mugnaini's group described in detail the novel direct projections from the rat auditory neocortex to various subcollicular auditory centers, including the nucleus sagulum, the paralemniscal regions, the superior olivary complex, and the cochlear nuclei (Feliciano et al., Auditory Neuroscience 1995; 1:287-308). This review gives Enrico Mugnaini credit for his seminal contribution to the knowledge of auditory corticosubcollicular projections and summarizes how this growing field has evolved in the last 20 years.
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Affiliation(s)
- Enrique Saldaña
- Neurohistology Laboratory, Neuroscience Institute of Castilla y León (INCyL), University of Salamanca, 37007, Salamanca, Spain. .,Department of Cell Biology and Pathology, Medical School, University of Salamanca, 37007, Salamanca, Spain. .,Institute of Biomedical Research of Salamanca (IBSAL), 37007, Salamanca, Spain.
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Roberts PD, Portfors CV. Responses to Social Vocalizations in the Dorsal Cochlear Nucleus of Mice. Front Syst Neurosci 2015; 9:172. [PMID: 26733824 PMCID: PMC4680083 DOI: 10.3389/fnsys.2015.00172] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2015] [Accepted: 11/26/2015] [Indexed: 11/18/2022] Open
Abstract
Identifying sounds is critical for an animal to make appropriate behavioral responses to environmental stimuli, including vocalizations from conspecifics. Identification of vocalizations may be supported by neuronal selectivity in the auditory pathway. The first place in the ascending auditory pathway where neuronal selectivity to vocalizations has been found is in the inferior colliculus (IC), but very few brainstem nuclei have been evaluated. Here, we tested whether selectivity to vocalizations is present in the dorsal cochlear nucleus (DCN). We recorded extracellular neural responses in the DCN of mice and found that fusiform cells responded in a heterogeneous and selective manner to mouse ultrasonic vocalizations. Most fusiform cells responded to vocalizations that contained spectral energy at much higher frequencies than the characteristic frequencies of the cells. To understand this mismatch of stimulus properties and frequency tuning of the cells, we developed a dynamic, nonlinear model of the cochlea that simulates cochlear distortion products on the basilar membrane. We preprocessed the vocalization stimuli through this model and compared responses to these distorted vocalizations with responses to the original vocalizations. We found that fusiform cells in the DCN respond in a heterogeneous manner to vocalizations, and that these neurons can use distortion products as a mechanism for encoding ultrasonic vocalizations. In addition, the selective neuronal responses were dependent on the presence of inhibitory sidebands that modulated the response depending on the temporal structure of the distortion product. These findings suggest that important processing of complex sounds occurs at a very early stage of central auditory processing and is not strictly a function of the cortex.
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Affiliation(s)
- Patrick D Roberts
- School of Biological Sciences and Integrative Physiology and Neuroscience, Washington State University Vancouver, WA, USA
| | - Christine V Portfors
- School of Biological Sciences and Integrative Physiology and Neuroscience, Washington State University Vancouver, WA, USA
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Jäger K, Kössl M. Corticofugal Modulation of DPOAEs in Gerbils. Hear Res 2015; 332:61-72. [PMID: 26619750 DOI: 10.1016/j.heares.2015.11.008] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/13/2015] [Revised: 10/20/2015] [Accepted: 11/09/2015] [Indexed: 01/13/2023]
Abstract
Efferent auditory feedback on cochlear hair cells is well studied regarding olivocochlear brainstem mechanisms. Less is known about how the descending corticofugal system may shape efferent feedback and modulate cochlear mechanics. Distortion-product otoacoustic emissions (DPOAEs) are a suitable tool to assess outer hair cell function, as they are by-products of the nonlinear cochlear amplification process. The present project investigates the effects of cortical activity on cubic and quadratic DPOAEs in mongolian gerbils, Meriones unguiculatus, through cortical deactivation using the sodium-channel blocker lidocaine. Contralateral cortical microinjections of lidocaine can lead to either an increase or decrease of median DPOAE levels of up to 10.95 dB. The effects are reversible and comparable at all tested frequencies (0.5-40 kHz). They are not restricted to the preferred frequency of the cortical site of injection. Recovery times are between 20 and 120 min depending on stimulation levels and emission type. When the injection is performed in the ipsilateral hemisphere, DPOAE level shifts are lower in amplitude compared to those after injection in the contralateral hemisphere. No significant changes in DPOAE levels are obtained after saline microinjections. Results indicate that deactivation of auditory cortex activity through lidocaine has a considerable impact on peripheral auditory responses in form of DPOAEs, probably through cortico-olivocochlear pathways.
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Affiliation(s)
- K Jäger
- Institute for Cell Biology and Neuroscience, Goethe University Frankfurt, Max-von-Laue Str. 13, 60438 Frankfurt, Germany.
| | - M Kössl
- Institute for Cell Biology and Neuroscience, Goethe University Frankfurt, Max-von-Laue Str. 13, 60438 Frankfurt, Germany.
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Distribution of glutamatergic, GABAergic, and glycinergic neurons in the auditory pathways of macaque monkeys. Neuroscience 2015; 310:128-51. [PMID: 26391919 DOI: 10.1016/j.neuroscience.2015.09.041] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2015] [Revised: 09/14/2015] [Accepted: 09/14/2015] [Indexed: 11/23/2022]
Abstract
Macaque monkeys use complex communication calls and are regarded as a model for studying the coding and decoding of complex sound in the auditory system. However, little is known about the distribution of excitatory and inhibitory neurons in the auditory system of macaque monkeys. In this study, we examined the overall distribution of cell bodies that expressed mRNAs for VGLUT1, and VGLUT2 (markers for glutamatergic neurons), GAD67 (a marker for GABAergic neurons), and GLYT2 (a marker for glycinergic neurons) in the auditory system of the Japanese macaque. In addition, we performed immunohistochemistry for VGLUT1, VGLUT2, and GAD67 in order to compare the distribution of proteins and mRNAs. We found that most of the excitatory neurons in the auditory brainstem expressed VGLUT2. In contrast, the expression of VGLUT1 mRNA was restricted to the auditory cortex (AC), periolivary nuclei, and cochlear nuclei (CN). The co-expression of GAD67 and GLYT2 mRNAs was common in the ventral nucleus of the lateral lemniscus (VNLL), CN, and superior olivary complex except for the medial nucleus of the trapezoid body, which expressed GLYT2 alone. In contrast, the dorsal nucleus of the lateral lemniscus, inferior colliculus, thalamus, and AC expressed GAD67 alone. The absence of co-expression of VGLUT1 and VGLUT2 in the medial geniculate, medial superior olive, and VNLL suggests that synaptic responses in the target neurons of these nuclei may be different between rodents and macaque monkeys.
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Baashar A, Robertson D, Mulders WH. A novel method for selectively labelling olivocochlear collaterals in the rat. Hear Res 2015; 325:35-41. [DOI: 10.1016/j.heares.2015.02.011] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/17/2014] [Revised: 02/23/2015] [Accepted: 02/25/2015] [Indexed: 10/23/2022]
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Offutt SJ, Ryan KJ, Konop AE, Lim HH. Suppression and facilitation of auditory neurons through coordinated acoustic and midbrain stimulation: investigating a deep brain stimulator for tinnitus. J Neural Eng 2014; 11:066001. [PMID: 25307351 PMCID: PMC4244264 DOI: 10.1088/1741-2560/11/6/066001] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
OBJECTIVE The inferior colliculus (IC) is the primary processing center of auditory information in the midbrain and is one site of tinnitus-related activity. One potential option for suppressing the tinnitus percept is through deep brain stimulation via the auditory midbrain implant (AMI), which is designed for hearing restoration and is already being implanted in deaf patients who also have tinnitus. However, to assess the feasibility of AMI stimulation for tinnitus treatment we first need to characterize the functional connectivity within the IC. Previous studies have suggested modulatory projections from the dorsal cortex of the IC (ICD) to the central nucleus of the IC (ICC), though the functional properties of these projections need to be determined. APPROACH In this study, we investigated the effects of electrical stimulation of the ICD on acoustic-driven activity within the ICC in ketamine-anesthetized guinea pigs. MAIN RESULTS We observed ICD stimulation induces both suppressive and facilitatory changes across ICC that can occur immediately during stimulation and remain after stimulation. Additionally, ICD stimulation paired with broadband noise stimulation at a specific delay can induce greater suppressive than facilitatory effects, especially when stimulating in more rostral and medial ICD locations. SIGNIFICANCE These findings demonstrate that ICD stimulation can induce specific types of plastic changes in ICC activity, which may be relevant for treating tinnitus. By using the AMI with electrode sites positioned with the ICD and the ICC, the modulatory effects of ICD stimulation can be tested directly in tinnitus patients.
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Affiliation(s)
- Sarah J. Offutt
- Department of Biomedical Engineering, University of Minnesota, Minneapolis, USA
| | - Kellie J. Ryan
- Department of Biomedical Engineering, University of Minnesota, Minneapolis, USA
| | - Alexander E. Konop
- Department of Biomedical Engineering, University of Minnesota, Minneapolis, USA
| | - Hubert H. Lim
- Department of Biomedical Engineering, University of Minnesota, Minneapolis, USA
- Institute for Translational Neuroscience, University of Minnesota, Minneapolis, USA
- Department of Otolaryngology, Head and Neck Surgery, University of Minnesota, Minneapolis, USA
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Muniak MA, Ryugo DK. Tonotopic organization of vertical cells in the dorsal cochlear nucleus of the CBA/J mouse. J Comp Neurol 2014; 522:937-49. [PMID: 23982998 DOI: 10.1002/cne.23454] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2013] [Revised: 07/30/2013] [Accepted: 08/16/2013] [Indexed: 11/12/2022]
Abstract
The systematic and topographic representation of frequency is a first principle of organization throughout the auditory system. The dorsal cochlear nucleus (DCN) receives direct tonotopic projections from the auditory nerve (AN) as well as secondary and descending projections from other sources. Among the recipients of AN input in the DCN are vertical cells (also called tuberculoventral cells), glycinergic interneurons thought to provide on- or near-best-frequency feed-forward inhibition to principal cells in the DCN and various cells in the anteroventral cochlear nucleus (AVCN). Differing lines of physiological and anatomical evidence suggest that vertical cells and their projections are organized with respect to frequency, but this has not been conclusively demonstrated in the intact mammalian brain. To address this issue, we retrogradely labeled vertical cells via physiologically targeted injections in the AVCN of the CBA/J mouse. Results from multiple cases were merged with a normalized 3D template of the cochlear nucleus (Muniak et al. [2013] J. Comp. Neurol. 521:1510-1532) to demonstrate quantitatively that the arrangement of vertical cells is tonotopic and aligned to the innervation pattern of the AN. These results suggest that vertical cells are well positioned for providing immediate, frequency-specific inhibition onto cells of the DCN and AVCN to facilitate spectral processing.
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Affiliation(s)
- Michael A Muniak
- Department of Neuroscience, Johns Hopkins University, Baltimore, Maryland, 21205; Hearing Research Program, Garvan Institute of Medical Research, Sydney, New South Wales, 2010, Australia
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Mylius J, Brosch M, Scheich H, Budinger E. Subcortical auditory structures in the Mongolian gerbil: I. Golgi architecture. J Comp Neurol 2013; 521:1289-321. [PMID: 23047461 DOI: 10.1002/cne.23232] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2012] [Revised: 08/25/2012] [Accepted: 10/02/2012] [Indexed: 12/17/2022]
Abstract
By means of the Golgi-Cox and Nissl methods we investigated the cyto- and fiberarchitecture as well as the morphology of neurons in the subcortical auditory structures of the Mongolian gerbil (Meriones unguiculatus), a frequently used animal model in auditory neuroscience. We describe the divisions and subdivisions of the auditory thalamus including the medial geniculate body, suprageniculate nucleus, and reticular thalamic nucleus, as well as of the inferior colliculi, nuclei of the lateral lemniscus, superior olivary complex, and cochlear nuclear complex. In this study, we 1) confirm previous results about the organization of the gerbil's subcortical auditory pathway using other anatomical staining methods (e.g., Budinger et al. [2000] Eur J Neurosci 12:2452-2474); 2) add substantially to the knowledge about the laminar and cellular organization of the gerbil's subcortical auditory structures, in particular about the orientation of their fibrodendritic laminae and about the morphology of their most distinctive neuron types; and 3) demonstrate that the cellular organization of these structures, as seen by the Golgi technique, corresponds generally to that of other mammalian species, in particular to that of rodents.
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Affiliation(s)
- Judith Mylius
- Special Laboratory Primate Neurobiology, Leibniz Institute for Neurobiology, D-39118 Magdeburg, Germany
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Budinger E, Brosch M, Scheich H, Mylius J. The subcortical auditory structures in the Mongolian gerbil: II. Frequency-related topography of the connections with cortical field AI. J Comp Neurol 2013; 521:2772-97. [DOI: 10.1002/cne.23314] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2012] [Revised: 12/20/2012] [Accepted: 01/23/2013] [Indexed: 11/07/2022]
Affiliation(s)
| | | | | | - Judith Mylius
- Special Laboratory for Primate Neurobiology; Leibniz Institute for Neurobiology; D-39118 Magdeburg; Germany
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Rodriguez-Diaz R, Caicedo A. Novel approaches to studying the role of innervation in the biology of pancreatic islets. Endocrinol Metab Clin North Am 2013; 42:39-56. [PMID: 23391238 PMCID: PMC3576136 DOI: 10.1016/j.ecl.2012.11.001] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
The autonomic nervous system helps regulate glucose homeostasis by acting on pancreatic islets of Langerhans. Despite decades of research on the innervation of the pancreatic islet, the mechanisms used by the autonomic nervous input to influence islet cell biology have not been elucidated. This article discusses how these barriers can be overcome to study the role of the autonomic innervation of the pancreatic islet in glucose metabolism. It describes recent advances in microscopy and novel approaches to studying the effects of nervous input that may help clarify how autonomic axons regulate islet biology.
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Affiliation(s)
- Rayner Rodriguez-Diaz
- Diabetes Research Institute, Miller School of Medicine, University of Miami, FL 33136
| | - Alejandro Caicedo
- Diabetes Research Institute, Miller School of Medicine, University of Miami, FL 33136
- Department of Medicine, Miller School of Medicine, University of Miami, FL 33136
- Department of Physiology and Biophysics, Miller School of Medicine, University of Miami, FL 33136
- Program in Neuroscience, Miller School of Medicine, University of Miami, FL 33136
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Iigaya K, Müller-Ribeiro FCDF, Horiuchi J, McDowall LM, Nalivaiko E, Fontes MAP, Dampney RAL. Synchronized activation of sympathetic vasomotor, cardiac, and respiratory outputs by neurons in the midbrain colliculi. Am J Physiol Regul Integr Comp Physiol 2012; 303:R599-610. [DOI: 10.1152/ajpregu.00205.2012] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The superior and inferior colliculi are believed to generate immediate and highly coordinated defensive behavioral responses to threatening visual and auditory stimuli. Activation of neurons in the superior and inferior colliculi have been shown to evoke increases in cardiovascular and respiratory activity, which may be components of more generalized stereotyped behavioral responses. In this study, we examined the possibility that there are “command neurons” within the colliculi that can simultaneously drive sympathetic and respiratory outputs. In anesthetized rats, microinjections of bicuculline (a GABAA receptor antagonist) into sites within a circumscribed region in the deep layers of the superior colliculus and in the central and external nuclei of the inferior colliculus evoked a response characterized by intense and highly synchronized bursts of renal sympathetic nerve activity (RSNA) and phrenic nerve activity (PNA). Each burst of RSNA had a duration of ∼300–400 ms and occurred slightly later (peak to peak latency of 41 ± 8 ms) than the corresponding burst of PNA. The bursts of RSNA and PNA were also accompanied by transient increases in arterial pressure and, in most cases, heart rate. Synchronized bursts of RSNA and PNA were also evoked after neuromuscular blockade, artificial ventilation, and vagotomy and so were not dependent on afferent feedback from the lungs. We propose that the synchronized sympathetic-respiratory responses are driven by a common population of neurons, which may normally be activated by an acute threatening stimulus.
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Affiliation(s)
- Kamon Iigaya
- School of Medical Sciences (Physiology) and Bosch Institute for Biomedical Research, University of Sydney, Australia
| | - Flávia Camargos de Figueirêdo Müller-Ribeiro
- School of Medical Sciences (Physiology) and Bosch Institute for Biomedical Research, University of Sydney, Australia
- Laboratório de Hipertensão, Departamento de Fisiologia e Biofísica, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Minas Gerais, Brazil
| | - Jouji Horiuchi
- School of Medical Sciences (Physiology) and Bosch Institute for Biomedical Research, University of Sydney, Australia
- Department of Biomedical Engineering, Toyo University, Saitama, Japan; and
| | - Lachlan M. McDowall
- School of Medical Sciences (Physiology) and Bosch Institute for Biomedical Research, University of Sydney, Australia
| | - Eugene Nalivaiko
- School of Biomedical Sciences and Pharmacy, University of Newcastle, Callaghan, Australia
| | - Marco A. P. Fontes
- Laboratório de Hipertensão, Departamento de Fisiologia e Biofísica, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Minas Gerais, Brazil
| | - Roger A. L. Dampney
- School of Medical Sciences (Physiology) and Bosch Institute for Biomedical Research, University of Sydney, Australia
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Kuwabara N. Neuroanatomical technique for studying long axonal projections in the central nervous system: combined axonal staining and pre-labeling in parasagittal gerbil brain slices. Biotech Histochem 2012; 87:413-22. [PMID: 22712444 DOI: 10.3109/10520295.2012.688868] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
A method is described for studying the morphological features of extensive axonal projections within the central nervous system of the gerbil, Meriones anguiculatus. Potentially long descending axonal projections between the auditory thalamus and lower brainstem were used as a model. The inferior colliculus (IC) in the tectum was injected in vivo with a fluorescent retrograde tracer, Fluoro-Gold, to label cells in the medial geniculate body (MGB) that had descending projections to the IC, and cells in the superior olivary complex (SOC) that had ascending projections to the IC. Another fluorescent retrograde tracer, fast blue, was injected into the cochlea to label olivocochlear (OC) cells in the SOC. Inferomedially curved parasagittal slices containing ipsilateral auditory cell groups from the thalamus to the brainstem were cut and descending axons of the pre-labeled MGB cells were traced anterogradely with Biocytin. After visualizing histologically the injected Biocytin, discretely labeled IC-projecting axons of the MGB cells were traced including their collaterals that extended further into the SOC. In the SOC, these axons terminated on pre-labeled cells including OC cells. The combination of anterograde and retrograde tracing in the slice preparations described here demonstrated extensive descending axonal projections from the thalamus to their targets in the lower brainstem that had known ascending/descending projections within the auditory system.
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Affiliation(s)
- N Kuwabara
- Department of Anatomical Sciences and Neurobiology, University of Louisville School of Medicine, Health Sciences Center, Kentucky 40292, USA.
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Darrow KN, Benson TE, Brown MC. Planar multipolar cells in the cochlear nucleus project to medial olivocochlear neurons in mouse. J Comp Neurol 2012; 520:1365-75. [PMID: 22101968 PMCID: PMC3514887 DOI: 10.1002/cne.22797] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Medial olivocochlear (MOC) neurons originate in the superior olivary complex and project to the cochlea, where they act to reduce the effects of noise masking and protect the cochlea from damage. MOC neurons respond to sound via a reflex pathway; however, in this pathway the cochlear nucleus cell type that provides input to MOC neurons is not known. We investigated whether multipolar cells of the ventral cochlear nucleus have projections to MOC neurons by labeling them with injections into the dorsal cochlear nucleus. The projections of one type of labeled multipolar cell, planar neurons, were traced into the ventral nucleus of the trapezoid body, where they were observed terminating on MOC neurons (labeled in some cases by a second cochlear injection of FluoroGold). These terminations formed what appear to be excitatory synapses, i.e., containing small, round vesicles and prominent postsynaptic densities. These data suggest that cochlear nucleus planar multipolar neurons drive the MOC neuron's response to sound.
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Affiliation(s)
- Keith N Darrow
- Department of Communication Sciences and Disorders, Worcester State University, Worcester, Massachusetts 01564, USA.
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Wang H, Yin G, Rogers K, Miralles C, De Blas AL, Rubio ME. Monaural conductive hearing loss alters the expression of the GluA3 AMPA and glycine receptor α1 subunits in bushy and fusiform cells of the cochlear nucleus. Neuroscience 2011; 199:438-51. [PMID: 22044924 DOI: 10.1016/j.neuroscience.2011.10.021] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2011] [Revised: 10/11/2011] [Accepted: 10/13/2011] [Indexed: 11/18/2022]
Abstract
The impact of conductive hearing loss (CHL), the second most common form of hearing loss, on neuronal plasticity in the central auditory pathway is unknown. After short-term (1 day) monaural earplugging, the GluA3 subunits of the AMPA receptor (AMPAR) are upregulated at auditory nerve synapses on the projection neurons of the cochlear nucleus; glycine receptor α1 (GlyRα1) subunits are downregulated at inhibitory synapses in the same neuronal population. These data suggest that CHL affects receptor trafficking at synapses. We examined the impact of 7 days of CHL on the general expression of excitatory and inhibitory receptors by quantitative biochemistry and immunohistochemistry, using specific antibodies to detect AMPAR subunits (GluA1, GluA2, GluA2/3, and GluA4), GlyRα1, and the GABA(A) receptor subunits β2/3. Following monaural earplugging and an elevation of the hearing threshold by approximately 35 dB, the immunolabeling of the antibody for the GluA2/3 subunits but not the GluA2 subunit increased on bushy cells (BCs) and fusiform cells (FCs) of the ipsilateral ventral and dorsal cochlear nuclei. These same cell types showed a downregulation of the GlyRα1 subunit. Similar results were observed in the contralateral nuclei. The expression levels of GABA(A) β2/3 were unchanged. These findings suggest that, following longer periods of monaural conductive hearing loss, the synthesis and subsequent composition of specific glutamate and glycine receptors in projection neurons and their synapses are altered; these changes may contribute to abnormal auditory processing.
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Affiliation(s)
- H Wang
- Department of Otolaryngology, University of Pittsburgh, 3501 5th Avenue BST3 10015, Pittsburgh, PA 15261, USA
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Otazu GH, Leibold C. A corticothalamic circuit model for sound identification in complex scenes. PLoS One 2011; 6:e24270. [PMID: 21931668 PMCID: PMC3172241 DOI: 10.1371/journal.pone.0024270] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2011] [Accepted: 08/07/2011] [Indexed: 11/29/2022] Open
Abstract
The identification of the sound sources present in the environment is essential for the survival of many animals. However, these sounds are not presented in isolation, as natural scenes consist of a superposition of sounds originating from multiple sources. The identification of a source under these circumstances is a complex computational problem that is readily solved by most animals. We present a model of the thalamocortical circuit that performs level-invariant recognition of auditory objects in complex auditory scenes. The circuit identifies the objects present from a large dictionary of possible elements and operates reliably for real sound signals with multiple concurrently active sources. The key model assumption is that the activities of some cortical neurons encode the difference between the observed signal and an internal estimate. Reanalysis of awake auditory cortex recordings revealed neurons with patterns of activity corresponding to such an error signal.
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Affiliation(s)
- Gonzalo H Otazu
- Division of Neurobiology, Department Biology II, Ludwig-Maximilians-Universität, Munich, Germany.
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Ito T, Bishop DC, Oliver DL. Expression of glutamate and inhibitory amino acid vesicular transporters in the rodent auditory brainstem. J Comp Neurol 2011; 519:316-40. [PMID: 21165977 DOI: 10.1002/cne.22521] [Citation(s) in RCA: 97] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Glutamate is the main excitatory neurotransmitter in the auditory system, but associations between glutamatergic neuronal populations and the distribution of their synaptic terminations have been difficult. Different subsets of glutamatergic terminals employ one of three vesicular glutamate transporters (VGLUT) to load synaptic vesicles. Recently, VGLUT1 and VGLUT2 terminals were found to have different patterns of organization in the inferior colliculus, suggesting that there are different types of glutamatergic neurons in the brainstem auditory system with projections to the colliculus. To positively identify VGLUT-expressing neurons as well as inhibitory neurons in the auditory brainstem, we used in situ hybridization to identify the mRNA for VGLUT1, VGLUT2, and VIAAT (the vesicular inhibitory amino acid transporter used by GABAergic and glycinergic terminals). Similar expression patterns were found in subsets of glutamatergic and inhibitory neurons in the auditory brainstem and thalamus of adult rats and mice. Four patterns of gene expression were seen in individual neurons. 1) VGLUT2 expressed alone was the prevalent pattern. 2) VGLUT1 coexpressed with VGLUT2 was seen in scattered neurons in most nuclei but was common in the medial geniculate body and ventral cochlear nucleus. 3) VGLUT1 expressed alone was found only in granule cells. 4) VIAAT expression was common in most nuclei but dominated in some. These data show that the expression of the VGLUT1/2 and VIAAT genes can identify different subsets of auditory neurons. This may facilitate the identification of different components in auditory circuits.
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Affiliation(s)
- Tetsufumi Ito
- Department of Anatomy, Faculty of Medical Sciences, University of Fukui, Fukui, Japan
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Aparicio MA, Viñuela A, Saldaña E. Projections from the inferior colliculus to the tectal longitudinal column in the rat. Neuroscience 2010; 166:653-64. [PMID: 20056139 DOI: 10.1016/j.neuroscience.2009.12.074] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2009] [Revised: 12/29/2009] [Accepted: 12/30/2009] [Indexed: 10/20/2022]
Abstract
We have used the anterograde tracer Phaseolus vulgaris-leucoagglutinin (PHA-L) to study with albino rats the projections from the inferior colliculus (IC) to the tectal longitudinal column (TLC), a newly discovered nucleus that spans the midbrain tectum longitudinally, on each side of the midbrain, immediately above the periaqueductal gray matter. We studied the projections of the medial IC, which includes the classical central nucleus (CNIC) and the dorsal cortex (DCIC), and those of the lateral IC, equivalent to the classical external cortex (ECIC). Following unilateral injections of PHA-L into the medial IC, numerous terminal fibers are labeled bilaterally in the TLC. The ipsilateral projection is denser and targets the entire nucleus, whereas the contralateral projection targets significantly only the caudal half or two-thirds of the TLC. Fibers from the medial IC reach the TLC by two routes: as collaterals of axons that travel in the commissure of the IC and as collaterals of thick ipsilateral colliculogeniculate axons; the latter travel through the deep superior colliculus on their way to the TLC. Within the TLC, individual IC fibers tend to run longitudinally. The injection of PHA-L into the lateral IC indicates that this subdivision sends a weak, bilateral projection to the TLC whose trajectory, morphology and distribution are similar to those of the projection from the medial IC. These results demonstrate that all subdivisions of the IC send projections to the TLC, suggesting that the IC may be one of the main sources of auditory input to this tectal nucleus.
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Affiliation(s)
- M-A Aparicio
- Laboratory for the Neurobiology of Hearing, Neuroscience Institute of Castilla y León, University of Salamanca, 37007-Salamanca, Spain
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