1
|
Szelényi A, Fava E. Long latency responses in tongue muscle elicited by various stimulation sites in anesthetized humans - New insights into tongue-related brainstem reflexes. Brain Stimul 2022; 15:566-575. [PMID: 35341967 DOI: 10.1016/j.brs.2022.03.003] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2021] [Revised: 03/15/2022] [Accepted: 03/16/2022] [Indexed: 11/02/2022] Open
Abstract
BACKGROUND Long Latency Responses (LLR) in tongue muscles are a scarcely described phenomenon, the physiology of which is uncertain. OBJECTIVES The aim of this exploratory, observational study was to describe tongue-LLR elicited by direct trigeminal nerve (DTNS), dorsal column (DoColS), transcranial electric (TES) and peripheral median nerve (MNS) stimulation in a total of 93 patients undergoing neurosurgical procedures under general anesthesia. METHODS Bilateral tongue responses were derived concurrently after each of the following stimulations: (1) DTNS applied with single monophasic or train-of-three pulses, ≤5 mA; (2) DoColS applied with a train-of-three pulses, ≤10 mA; (3) TES consisting of an anodal train-of-five stimulation, ≤250 mA; (4) MNS at wrist consisting of single or train-of-three monophasic pulses, ≤50 mA. Polyphasic tongue muscle responses exceeding the latencies of tongue compound muscle action potentials or motor evoked potentials were classified as LLR. RESULTS Tongue-LLR were evoked from all stimulation sites, with latencies as follows: (1) DTNS: solely ipsilateral 20.2 ± 3.3 msec; (2) DoColS: ipsilateral 25.9 ± 1.6 msec, contralateral 25.1 ± 4.2 msec; (3) TES: contralateral 55.3 ± 10.2 msec, ipsilateral 54.9 ± 12.0 msec; (4) MNS: ipsilateral 37.8 ± 4.7 msec and contralateral 40.3 ± 3.5 msec. CONCLUSION The tongue muscles are a common efferent in brainstem pathways targeted by trigeminal and cervical sensory fibers. DTNS can elicit the "trigemino-hypoglossal-reflex". For the MNS elicited tongue-LLR, we propose the term "somatosensory-evoked tongue-reflex". Although the origin of the TES related tongue-LLR remains unclear, these data will help to interpret intraoperative tongue recordings.
Collapse
Affiliation(s)
- Andrea Szelényi
- Department of Neurosurgery, University Hospital, LMU Munich, Munich, Germany.
| | - Enrica Fava
- Department of Neurosurgery, Great Metropolitan Hospital of Niguarda, University of Milano, Italy
| |
Collapse
|
2
|
Mirallave Pescador A, Téllez MJ, Sánchez Roldán MDLÁ, Samusyte G, Lawson EC, Coelho P, Lejarde A, Rathore A, Le D, Ulkatan S. Methodology for eliciting the brainstem trigeminal-hypoglossal reflex in humans under general anesthesia. Clin Neurophysiol 2022; 137:1-10. [DOI: 10.1016/j.clinph.2022.02.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2021] [Revised: 02/05/2022] [Accepted: 02/11/2022] [Indexed: 11/03/2022]
|
3
|
Mercer Lindsay N, Knutsen PM, Lozada AF, Gibbs D, Karten HJ, Kleinfeld D. Orofacial Movements Involve Parallel Corticobulbar Projections from Motor Cortex to Trigeminal Premotor Nuclei. Neuron 2019; 104:765-780.e3. [PMID: 31587918 DOI: 10.1016/j.neuron.2019.08.032] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2019] [Revised: 07/07/2019] [Accepted: 08/19/2019] [Indexed: 01/21/2023]
Abstract
How do neurons in orofacial motor cortex (MCtx) orchestrate behaviors? We show that focal activation of MCtx corticobulbar neurons evokes behaviorally relevant concurrent movements of the forelimb, jaw, nose, and vibrissae. The projections from different locations in MCtx form gradients of boutons across premotor nuclei spinal trigeminal pars oralis (SpVO) and interpolaris rostralis (SpVIr). Furthermore, retrograde viral tracing from muscles that control orofacial actions shows that these premotor nuclei segregate their outputs. In the most dramatic case, both SpVO and SpVIr are premotor to forelimb and vibrissa muscles, while only SpVO is premotor to jaw muscles. Functional confirmation of the superimposed control by MCtx was obtained through selective optogenetic activation of corticobulbar neurons on the basis of their preferential projections to SpVO versus SpVIr. We conclude that neighboring projection neurons in orofacial MCtx form parallel pathways to distinct pools of trigeminal premotor neurons that coordinate motor actions into a behavior.
Collapse
Affiliation(s)
- Nicole Mercer Lindsay
- Section of Neurobiology, University of California, San Diego, La Jolla, CA 92093, USA
| | - Per M Knutsen
- Department of Physics, University of California, San Diego, La Jolla, CA 92093, USA
| | - Adrian F Lozada
- Department of Physics, University of California, San Diego, La Jolla, CA 92093, USA
| | - Daniel Gibbs
- Department of Neurosciences, University of California, San Diego, La Jolla, CA 92093, USA
| | - Harvey J Karten
- Department of Neurosciences, University of California, San Diego, La Jolla, CA 92093, USA
| | - David Kleinfeld
- Section of Neurobiology, University of California, San Diego, La Jolla, CA 92093, USA; Department of Physics, University of California, San Diego, La Jolla, CA 92093, USA.
| |
Collapse
|
4
|
Li JN, Sun Y, Ji SL, Chen YB, Ren JH, He CB, Wu ZY, Li H, Dong YL, Li YQ. Collateral Projections from the Medullary Dorsal Horn to the Ventral Posteromedial Thalamic Nucleus and the Parafascicular Thalamic Nucleus in the Rat. Neuroscience 2019; 410:293-304. [PMID: 31075313 DOI: 10.1016/j.neuroscience.2019.04.050] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2018] [Revised: 04/24/2019] [Accepted: 04/26/2019] [Indexed: 10/26/2022]
Abstract
Medullary dorsal horn (MDH), the homolog of spinal dorsal horn, plays essential roles in processing of nociceptive signals from orofacial region toward higher centers, such as the ventral posteromedial thalamic nucleus (VPM) and parafascicular thalamic nucleus (Pf), which belong to the sensory-discriminative and affective aspects of pain transmission systems at the thalamic level, respectively. In the present study, in order to provide morphological evidence for whether neurons in the MDH send collateral projections to the VPM and Pf, a retrograde double tracing method combined with immunofluorescence staining for substance P (SP), SP receptor (SPR) and Fos protein was used. Fluoro-gold (FG) was injected into the VPM and the tetramethylrhodamine-dextran (TMR) was injected into the Pf. The result revealed that both FG- and TMR-labeled projection neurons were observed throughout the entire extent of the MDH, while the FG/TMR double-labeled neurons were mainly located in laminae I and III. It was also found that some of the FG/TMR double-labeled neurons within lamina I expressed SPR and were in close contact with SP-immunoreactive (SP-ir) terminals. After formalin injection into the orofacial region, 41.4% and 34.3% of the FG/TMR double-labeled neurons expressed Fos protein in laminae I and III, respectively. The present results provided morphological evidence for that some SPR-expressing neurons within the MDH send collateral projections to both VPM and Pf and might be involved in sensory-discriminative and affective aspects of acute orofacial nociceptive information transmission.
Collapse
Affiliation(s)
- Jia-Ni Li
- Department of Anatomy, Histology and Embryology & K. K. Leung Brain Research Centre, The Fourth Military Medical University, Xi'an 710032, China
| | - Yi Sun
- Department of Human Anatomy, Histology and Embryology, Fujian Medical University, Fuzhou 350108, China
| | - Song-Ling Ji
- Department of Anatomy, The Zunyi Medical Collage, Zunyi 563000, China
| | - Yan-Bing Chen
- Department of Human Anatomy, Histology and Embryology, Fujian Medical University, Fuzhou 350108, China
| | - Jia-Hao Ren
- Department of Anatomy, Histology and Embryology & K. K. Leung Brain Research Centre, The Fourth Military Medical University, Xi'an 710032, China
| | - Cheng-Bo He
- Department of Anatomy, The Zunyi Medical Collage, Zunyi 563000, China
| | - Zhen-Yu Wu
- Department of Anatomy, Histology and Embryology & K. K. Leung Brain Research Centre, The Fourth Military Medical University, Xi'an 710032, China
| | - Hui Li
- Department of Anatomy, Histology and Embryology & K. K. Leung Brain Research Centre, The Fourth Military Medical University, Xi'an 710032, China
| | - Yu-Lin Dong
- Department of Anatomy, Histology and Embryology & K. K. Leung Brain Research Centre, The Fourth Military Medical University, Xi'an 710032, China.
| | - Yun-Qing Li
- Department of Anatomy, Histology and Embryology & K. K. Leung Brain Research Centre, The Fourth Military Medical University, Xi'an 710032, China; Joint Laboratory of Neuroscience at Hainan Medical University and The Fourth Military Medical University, Hainan Medical University, Haikou 571199, China.
| |
Collapse
|
5
|
Supratrigeminal Bilaterally Projecting Neurons Maintain Basal Tone and Enable Bilateral Phasic Activation of Jaw-Closing Muscles. J Neurosci 2017; 36:7663-75. [PMID: 27445144 DOI: 10.1523/jneurosci.0839-16.2016] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2016] [Accepted: 06/07/2016] [Indexed: 11/21/2022] Open
Abstract
UNLABELLED Anatomical studies have identified brainstem neurons that project bilaterally to left and right oromotor pools, which could potentially mediate bilateral muscle coordination. We use retrograde lentiviruses combined with a split-intein-mediated split-Cre-recombinase system in mice to isolate, characterize, and manipulate a population of neurons projecting to both the left and right jaw-closing trigeminal motoneurons. We find that these bilaterally projecting premotor neurons (BPNs) reside primarily in the supratrigeminal nucleus (SupV) and the parvicellular and intermediate reticular regions dorsal to the facial motor nucleus. These BPNs also project to multiple midbrain and brainstem targets implicated in orofacial sensorimotor control, and consist of a mix of glutamatergic, GABAergic, and glycinergic neurons, which can drive both excitatory and inhibitory inputs to trigeminal motoneurons when optogenetically activated in slice. Silencing BPNs with tetanus toxin light chain (TeNT) increases bilateral masseter activation during chewing, an effect driven by the expression of TeNT in SupV BPNs. Acute unilateral optogenetic inhibition of SupV BPNs identifies a group of tonically active neurons that function to lower masseter muscle tone, whereas unilateral optogenetic activation of SupV BPNs is sufficient to induce bilateral masseter activation both during resting state and during chewing. These results provide evidence for SupV BPNs in tonically modulating jaw-closing muscle tone and in mediating bilateral jaw closing. SIGNIFICANCE STATEMENT We developed a method that combines retrograde lentiviruses with the split-intein-split-Cre system in mice to isolate, characterize, and manipulate neurons that project to both left and right jaw-closing motoneurons. We show that these bilaterally projecting premotor neurons (BPNs) reside primarily in the supratrigeminal nucleus and the rostral parvicellular and intermediate reticular nuclei. BPNs consist of both excitatory and inhibitory populations, and also project to multiple brainstem nuclei implicated in orofacial sensorimotor control. Manipulation of the supratrigeminal BPNs during natural jaw-closing behavior reveals a dual role for these neurons in eliciting phasic muscle activation and in maintaining basal muscle tone. The retrograde lentivirus carrying the split-intein-split-Cre system can be applied to study any neurons with bifurcating axons innervating two brain regions.
Collapse
|
6
|
Urban PP. Trigeminal-hypoglossal silent period: A pontomedullary brainstem reflex. Muscle Nerve 2015; 51:538-40. [DOI: 10.1002/mus.24349] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/18/2014] [Indexed: 01/24/2023]
Affiliation(s)
- Peter P. Urban
- Department of Neurology; Asklepios Klinik Barmbek; Rübenkamp 220 22291 Hamburg Germany
| |
Collapse
|
7
|
Wang J, Zhang H, Feng YP, Meng H, Wu LP, Wang W, Li H, Zhang T, Zhang JS, Li YQ. Morphological evidence for a neurotensinergic periaqueductal gray-rostral ventromedial medulla-spinal dorsal horn descending pathway in rat. Front Neuroanat 2014; 8:112. [PMID: 25346662 PMCID: PMC4191475 DOI: 10.3389/fnana.2014.00112] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2014] [Accepted: 09/22/2014] [Indexed: 01/03/2023] Open
Abstract
Neurotensin (NT) is an endogenous neuropeptide that exerts potent opioid-independent analgesic effects, most likely via the type 2 NT receptor (NTR2). Previous morphological and electrophysiological studies suggested that the NT-NTR2 system is primarily localized in structures that constitute the descending pain control pathway, such as the periaqueductal gray (PAG), the rostral ventromedial medulla (RVM), and the spinal dorsal horn (SDH). However, relevant morphological evidence for this neurotensinergic (NTergic) circuit is lacking. Thus, the aim of the present study was to morphologically elucidate the potential sites and connections in the NT-NTR2 system that are involved in the descending pain control pathway. Based on light and electron microscopy combined with anterograde and retrograde tracing, we found evidence that NTR2-immunoreactive (IR) neurons in the RVM receive NT-IR projections originating from the PAG; express NT, serotonin (5-HT), or both; and send projections that terminate in laminae I and II of the SDH. These results suggest that NTR2 may contribute to pain control by binding to NT in the PAG-RVM-SDH pathway. In conclusion, our data provide morphological evidence for an NTergic PAG-RVM-SDH pathway, implicating novel mechanisms of NT-induced analgesia.
Collapse
Affiliation(s)
- Jian Wang
- Department of Anatomy, Histology and Embryology & K.K. Leung Brain Research Centre, Preclinical School of Medicine, The Fourth Military Medical University Xi'an, China
| | - Hua Zhang
- Department of Geriatrics, Xijing Hospital, The Fourth Military Medical University Xi'an, China
| | - Yu-Peng Feng
- Department of Anatomy, Histology and Embryology & K.K. Leung Brain Research Centre, Preclinical School of Medicine, The Fourth Military Medical University Xi'an, China
| | - Hua Meng
- Department of Geriatrics, Xijing Hospital, The Fourth Military Medical University Xi'an, China
| | - Li-Ping Wu
- Department of Geriatrics, Xijing Hospital, The Fourth Military Medical University Xi'an, China
| | - Wen Wang
- Department of Anatomy, Histology and Embryology & K.K. Leung Brain Research Centre, Preclinical School of Medicine, The Fourth Military Medical University Xi'an, China
| | - Hui Li
- Department of Anatomy, Histology and Embryology & K.K. Leung Brain Research Centre, Preclinical School of Medicine, The Fourth Military Medical University Xi'an, China
| | - Ting Zhang
- Department of Anatomy, Histology and Embryology & K.K. Leung Brain Research Centre, Preclinical School of Medicine, The Fourth Military Medical University Xi'an, China
| | - Jin-Shan Zhang
- Department of Anatomy, Histology and Embryology & K.K. Leung Brain Research Centre, Preclinical School of Medicine, The Fourth Military Medical University Xi'an, China
| | - Yun-Qing Li
- Department of Anatomy, Histology and Embryology & K.K. Leung Brain Research Centre, Preclinical School of Medicine, The Fourth Military Medical University Xi'an, China
| |
Collapse
|
8
|
Gunaydin LA, Grosenick L, Finkelstein JC, Kauvar IV, Fenno LE, Adhikari A, Lammel S, Mirzabekov JJ, Airan RD, Zalocusky KA, Tye KM, Anikeeva P, Malenka RC, Deisseroth K. Natural neural projection dynamics underlying social behavior. Cell 2014; 157:1535-51. [PMID: 24949967 DOI: 10.1016/j.cell.2014.05.017] [Citation(s) in RCA: 878] [Impact Index Per Article: 87.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2014] [Revised: 04/30/2014] [Accepted: 05/12/2014] [Indexed: 01/11/2023]
Abstract
Social interaction is a complex behavior essential for many species and is impaired in major neuropsychiatric disorders. Pharmacological studies have implicated certain neurotransmitter systems in social behavior, but circuit-level understanding of endogenous neural activity during social interaction is lacking. We therefore developed and applied a new methodology, termed fiber photometry, to optically record natural neural activity in genetically and connectivity-defined projections to elucidate the real-time role of specified pathways in mammalian behavior. Fiber photometry revealed that activity dynamics of a ventral tegmental area (VTA)-to-nucleus accumbens (NAc) projection could encode and predict key features of social, but not novel object, interaction. Consistent with this observation, optogenetic control of cells specifically contributing to this projection was sufficient to modulate social behavior, which was mediated by type 1 dopamine receptor signaling downstream in the NAc. Direct observation of deep projection-specific activity in this way captures a fundamental and previously inaccessible dimension of mammalian circuit dynamics.
Collapse
Affiliation(s)
- Lisa A Gunaydin
- Department of Bioengineering, Stanford University, Stanford, CA 94305, USA
| | - Logan Grosenick
- Department of Bioengineering, Stanford University, Stanford, CA 94305, USA; Neuroscience Program, Stanford University, Stanford, CA 94305, USA
| | - Joel C Finkelstein
- Department of Bioengineering, Stanford University, Stanford, CA 94305, USA
| | - Isaac V Kauvar
- Department of Bioengineering, Stanford University, Stanford, CA 94305, USA
| | - Lief E Fenno
- Department of Bioengineering, Stanford University, Stanford, CA 94305, USA; Neuroscience Program, Stanford University, Stanford, CA 94305, USA
| | - Avishek Adhikari
- Department of Bioengineering, Stanford University, Stanford, CA 94305, USA
| | - Stephan Lammel
- Department of Psychiatry and Behavioral Sciences, Stanford University, Stanford, CA 94305, USA
| | - Julie J Mirzabekov
- Department of Bioengineering, Stanford University, Stanford, CA 94305, USA
| | - Raag D Airan
- Department of Bioengineering, Stanford University, Stanford, CA 94305, USA
| | - Kelly A Zalocusky
- Department of Bioengineering, Stanford University, Stanford, CA 94305, USA; Neuroscience Program, Stanford University, Stanford, CA 94305, USA
| | - Kay M Tye
- Department of Bioengineering, Stanford University, Stanford, CA 94305, USA
| | - Polina Anikeeva
- Department of Bioengineering, Stanford University, Stanford, CA 94305, USA
| | - Robert C Malenka
- Department of Psychiatry and Behavioral Sciences, Stanford University, Stanford, CA 94305, USA
| | - Karl Deisseroth
- Department of Bioengineering, Stanford University, Stanford, CA 94305, USA; Department of Psychiatry and Behavioral Sciences, Stanford University, Stanford, CA 94305, USA; Howard Hughes Medical Institute, Stanford University, Stanford, CA 94305, USA.
| |
Collapse
|
9
|
Dong YL, Wang W, Li H, Li ZH, Zhang FX, Zhang T, Lu YC, Li JL, Wu SX, Li YQ. Neurochemical properties of the synapses in the pathways of orofacial nociceptive reflexes. PLoS One 2012; 7:e34435. [PMID: 22479630 PMCID: PMC3315548 DOI: 10.1371/journal.pone.0034435] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2011] [Accepted: 02/28/2012] [Indexed: 11/18/2022] Open
Abstract
The brainstem premotor neurons of the facial nucleus (VII) and hypoglossal (XII) nucleus can integrate orofacial nociceptive input from the caudal spinal trigeminal nucleus (Vc) and coordinate orofacial nociceptive reflex (ONR) responses. However, the synaptoarchitectures of the ONR pathways are still unknown. In the current study, we examined the distribution of GABAergic premotor neurons in the brainstem local ONR pathways, their connections with the Vc projections joining the brainstem ONR pathways and the neurochemical properties of these connections. Retrograde tracer fluoro-gold (FG) was injected into the VII or XII, and anterograde tracer biotinylated dextran amine (BDA) was injected into the Vc. Immunofluorescence histochemical labeling for inhibitory/excitatory neurotransmitters combined with BDA/FG tracing showed that GABAergic premotor neurons were mainly distributed bilaterally in the ponto-medullary reticular formation with an ipsilateral dominance. Some GABAergic premotor neurons made close appositions to the BDA-labeled fibers coming from the Vc, and these appostions were mainly distributed in the parvicellular reticular formation (PCRt), dorsal medullary reticular formation (MdD), and supratrigeminal nucleus (Vsup). We further examined the synaptic relationships between the Vc projecting fibers and premotor neurons in the VII or XII under the confocal laser-scanning microscope and electron microscope, and found that the BDA-labeled axonal terminals that made asymmetric synapses on premotor neurons showed vesicular glutamate transporter 2 (VGluT2) like immunoreactivity. These results indicate that the GABAergic premotor neurons receive excitatory neurotransmission from the Vc and may contribute to modulating the generation of the tonic ONR.
Collapse
Affiliation(s)
- Yu-lin Dong
- Department of Anatomy and Histology and Embryology, and K. K. Leung Brain Research Centre, The Fourth Military Medical University, Xi'an, China
| | - Wen Wang
- Department of Anatomy and Histology and Embryology, and K. K. Leung Brain Research Centre, The Fourth Military Medical University, Xi'an, China
| | - Hui Li
- Department of Anatomy and Histology and Embryology, and K. K. Leung Brain Research Centre, The Fourth Military Medical University, Xi'an, China
| | - Zhi-hong Li
- Department of Anatomy and Histology and Embryology, and K. K. Leung Brain Research Centre, The Fourth Military Medical University, Xi'an, China
| | - Fu-xing Zhang
- Department of Anatomy and Histology and Embryology, and K. K. Leung Brain Research Centre, The Fourth Military Medical University, Xi'an, China
| | - Ting Zhang
- Department of Anatomy and Histology and Embryology, and K. K. Leung Brain Research Centre, The Fourth Military Medical University, Xi'an, China
| | - Ya-cheng Lu
- Department of Anatomy and Histology and Embryology, and K. K. Leung Brain Research Centre, The Fourth Military Medical University, Xi'an, China
| | - Jin-lian Li
- Department of Anatomy and Histology and Embryology, and K. K. Leung Brain Research Centre, The Fourth Military Medical University, Xi'an, China
- * E-mail: (JL); (SW); (YL)
| | - Sheng-xi Wu
- Department of Anatomy and Histology and Embryology, and K. K. Leung Brain Research Centre, The Fourth Military Medical University, Xi'an, China
- * E-mail: (JL); (SW); (YL)
| | - Yun-qing Li
- Department of Anatomy and Histology and Embryology, and K. K. Leung Brain Research Centre, The Fourth Military Medical University, Xi'an, China
- * E-mail: (JL); (SW); (YL)
| |
Collapse
|
10
|
Pan YA, Choy M, Prober DA, Schier AF. Robo2 determines subtype-specific axonal projections of trigeminal sensory neurons. Development 2011; 139:591-600. [PMID: 22190641 DOI: 10.1242/dev.076588] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
How neurons connect to form functional circuits is central to the understanding of the development and function of the nervous system. In the somatosensory system, perception of sensory stimuli to the head requires specific connections between trigeminal sensory neurons and their many target areas in the central nervous system. Different trigeminal subtypes have specialized functions and downstream circuits, but it has remained unclear how subtype-specific axonal projection patterns are formed. Using zebrafish as a model system, we followed the development of two trigeminal sensory neuron subtypes: one that expresses trpa1b, a nociceptive channel important for sensing environmental chemicals; and a distinct subtype labeled by an islet1 reporter (Isl1SS). We found that Trpa1b and Isl1SS neurons have overall similar axon trajectories but different branching morphologies and distributions of presynaptic sites. Compared with Trpa1b neurons, Isl1SS neurons display reduced branch growth and synaptogenesis at the hindbrain-spinal cord junction. The subtype-specific morphogenesis of Isl1SS neurons depends on the guidance receptor Robo2. robo2 is preferentially expressed in the Isl1SS subset and inhibits branch growth and synaptogenesis. In the absence of Robo2, Isl1SS afferents acquire many of the characteristics of Trpa1b afferents. These results reveal that subtype-specific activity of Robo2 regulates subcircuit morphogenesis in the trigeminal sensory system.
Collapse
Affiliation(s)
- Y Albert Pan
- Department of Molecular and Cellular Biology, Harvard University, 16 Divinity Avenue, Cambridge, MA 02138, USA.
| | | | | | | |
Collapse
|