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Ciralli B, Malfatti T, Hilscher MM, Leao RN, Cederroth CR, Leao KE, Kullander K. Unraveling the role of Slc10a4 in auditory processing and sensory motor gating: Implications for neuropsychiatric disorders? Prog Neuropsychopharmacol Biol Psychiatry 2024; 131:110930. [PMID: 38160852 DOI: 10.1016/j.pnpbp.2023.110930] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/15/2023] [Revised: 11/28/2023] [Accepted: 12/23/2023] [Indexed: 01/03/2024]
Abstract
BACKGROUND Psychiatric disorders, such as schizophrenia, are complex and challenging to study, partly due to the lack of suitable animal models. However, the absence of the Slc10a4 gene, which codes for a monoaminergic and cholinergic associated vesicular transporter protein, in knockout mice (Slc10a4-/-), leads to the accumulation of extracellular dopamine. A major challenge for studying schizophrenia is the lack of suitable animal models that accurately represent the disorder. We sought to overcome this challenge by using Slc10a4-/- mice as a potential model, considering their altered dopamine levels. This makes them a potential animal model for schizophrenia, a disorder known to be associated with altered dopamine signaling in the brain. METHODS The locomotion, auditory sensory filtering and prepulse inhibition (PPI) of Slc10a4-/- mice were quantified and compared to wildtype (WT) littermates. Intrahippocampal electrodes were used to record auditory event-related potentials (aERPs) for quantifying sensory filtering in response to paired-clicks. The channel above aERPs phase reversal was chosen for reliably comparing results between animals, and aERPs amplitude and latency of click responses were quantified. WT and Slc10a4-/- mice were also administered subanesthetic doses of ketamine to provoke psychomimetic behavior. RESULTS Baseline locomotion during auditory stimulation was similar between Slc10a4-/- mice and WT littermates. In WT animals, normal auditory processing was observed after i.p saline injections, and it was maintained under the influence of 5 mg/kg ketamine, but disrupted by 20 mg/kg ketamine. On the other hand, Slc10a4-/- mice did not show significant differences between N40 S1 and S2 amplitude responses in saline or low dose ketamine treatment. Auditory gating was considered preserved since the second N40 peak was consistently suppressed, but with increased latency. The P80 component showed higher amplitude, with shorter S2 latency under saline and 5 mg/kg ketamine treatment in Slc10a4-/- mice, which was not observed in WT littermates. Prepulse inhibition was also decreased in Slc10a4-/- mice when the longer interstimulus interval of 100 ms was applied, compared to WT littermates. CONCLUSION The Slc10a4-/- mice responses indicate that cholinergic and monoaminergic systems participate in the PPI magnitude, in the temporal coding (response latency) of the auditory sensory gating component N40, and in the amplitude of aERPs P80 component. These results suggest that Slc10a4-/- mice can be considered as potential models for neuropsychiatric conditions.
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Affiliation(s)
- Barbara Ciralli
- Brain Institute, Federal University of Rio Grande do Norte, Natal, RN, Brazil; Department of Immunology, Genetics and Pathology, Programme in Genomics and Neurobiology, Uppsala University, Uppsala, Sweden
| | - Thawann Malfatti
- Brain Institute, Federal University of Rio Grande do Norte, Natal, RN, Brazil; Department of Immunology, Genetics and Pathology, Programme in Genomics and Neurobiology, Uppsala University, Uppsala, Sweden; Experimental Audiology, Department of Physiology and Pharmacology, Karolinska Institutet, 171 77 Stockholm, Sweden
| | - Markus M Hilscher
- Institute for Analysis and Scientific Computing, Vienna University of Technology, Vienna, Austria
| | - Richardson N Leao
- Brain Institute, Federal University of Rio Grande do Norte, Natal, RN, Brazil; Department of Immunology, Genetics and Pathology, Programme in Genomics and Neurobiology, Uppsala University, Uppsala, Sweden
| | - Christopher R Cederroth
- Experimental Audiology, Department of Physiology and Pharmacology, Karolinska Institutet, 171 77 Stockholm, Sweden
| | - Katarina E Leao
- Brain Institute, Federal University of Rio Grande do Norte, Natal, RN, Brazil; Department of Immunology, Genetics and Pathology, Programme in Genomics and Neurobiology, Uppsala University, Uppsala, Sweden
| | - Klas Kullander
- Department of Immunology, Genetics and Pathology, Programme in Genomics and Neurobiology, Uppsala University, Uppsala, Sweden.
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Leung LS, Ma J. Medial Septum Modulates Consciousness and Psychosis-Related Behaviors Through Hippocampal Gamma Activity. Front Neural Circuits 2022; 16:895000. [PMID: 35874429 PMCID: PMC9301478 DOI: 10.3389/fncir.2022.895000] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2022] [Accepted: 06/16/2022] [Indexed: 11/13/2022] Open
Abstract
Abnormally high-amplitude hippocampal gamma activity (30–100 Hz) in behaving animals is seen after a hippocampal seizure, following injection of phencyclidine (PCP) or ketamine, and transiently in a delirium stage during induction of general anesthesia. High-amplitude hippocampal gamma activity in behaving rats is associated with hyperactive behavior and impairment in sensorimotor gating and sensory gating. The medial septum is necessary for the high-amplitude gamma activity and abnormal behaviors observed following a hippocampal seizure or injection of PCP/ketamine. Glutamatergic projection of the hippocampus to the nucleus accumbens (NAC) and dopaminergic transmission in NAC is necessary for abnormal behaviors. Large hippocampal gamma waves are suggested to contribute to seizure-induced automatism following temporal lobe seizures, and the schizophrenia-like symptoms induced by PCP/ketamine. Low-amplitude gamma activity is found during general anesthesia, associated with loss of consciousness in humans and loss of righting reflex in animals. Local inactivation or lesion of the medial septum, NAC, and brain areas connected to the septohippocampal-NAC system attenuates the increase in hippocampal gamma and associated behavioral disruptions induced by hippocampal seizure or PCP/ketamine. Inactivation or lesion of the septohippocampal-NAC system decreases the dose of anesthetic necessary for gamma decrease and loss of consciousness in animals. Thus, it is proposed that the septohippocampal-NAC system serves to control consciousness and the behavioral hyperactivity and neural dysfunctions during psychosis.
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de la Salle S, Choueiry J, McIntosh J, Bowers H, Ilivitsky V, Knott V. N-methyl-D-aspartate receptor antagonism impairs sensory gating in the auditory cortex in response to speech stimuli. Psychopharmacology (Berl) 2022; 239:2155-2169. [PMID: 35348805 DOI: 10.1007/s00213-022-06090-z] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/14/2021] [Accepted: 02/15/2022] [Indexed: 10/18/2022]
Abstract
Deficits in early auditory sensory processing in schizophrenia have been linked to N-methyl-D-aspartate receptor (NMDAR) hypofunction, but the role of NMDARs in aberrant auditory sensory gating (SG) in this disorder is unclear. This study, conducted in 22 healthy humans, examined the acute effects of a subanesthetic dose of the NMDAR antagonist ketamine on SG as measured electrophysiologically by suppression of the P50 event-related potential (ERP) to the second (S2) relative to the first (S1) of two closely paired (500 ms) identical speech stimuli. Ketamine induced impairment in SG indices at sensor (scalp)-level and at source-level in the auditory cortex (as assessed with eLORETA). Together with preliminary evidence of modest positive associations between impaired gating and dissociative symptoms elicited by ketamine, tentatively support a model of NMDAR hypofunction underlying disturbances in auditory SG in schizophrenia.
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Affiliation(s)
- Sara de la Salle
- The Royal's Institute of Mental Health Research, Royal Ottawa Mental Health Centre, 1145 Carling Avenue, Ottawa, ON, K1Z 7K4, Canada
| | - Joelle Choueiry
- The Royal's Institute of Mental Health Research, Royal Ottawa Mental Health Centre, 1145 Carling Avenue, Ottawa, ON, K1Z 7K4, Canada.,Department of Cellular and Molecular Medicine, University of Ottawa, Ottawa, ON, Canada
| | - Judy McIntosh
- The Royal's Institute of Mental Health Research, Royal Ottawa Mental Health Centre, 1145 Carling Avenue, Ottawa, ON, K1Z 7K4, Canada
| | - Hayley Bowers
- Department of Psychology, University of Guelph, Guelph, ON, Canada
| | - Vadim Ilivitsky
- The Royal's Institute of Mental Health Research, Royal Ottawa Mental Health Centre, 1145 Carling Avenue, Ottawa, ON, K1Z 7K4, Canada
| | - Verner Knott
- The Royal's Institute of Mental Health Research, Royal Ottawa Mental Health Centre, 1145 Carling Avenue, Ottawa, ON, K1Z 7K4, Canada. .,Department of Cellular and Molecular Medicine, University of Ottawa, Ottawa, ON, Canada.
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Leung LS, Ma J. Medial septum modulates hippocampal gamma activity and prepulse inhibition in an N-methyl-d-aspartate receptor antagonist model of schizophrenia. Schizophr Res 2018; 198:36-44. [PMID: 28801194 DOI: 10.1016/j.schres.2017.07.053] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/01/2017] [Revised: 07/25/2017] [Accepted: 07/28/2017] [Indexed: 01/07/2023]
Abstract
We reviewed the participation of the septohippocampal system in an animal model of schizophrenia that was acutely induced by systemic injection of an N-methyl-d-aspartate (NMDA) receptor antagonist such as phencyclidine, MK-801 and ketamine. The NMDA receptor antagonist-induced model of schizophrenia is characterized by behavioral and electrophysiological disruptions, including a decrease in prepulse inhibition of the acoustic startle response (PPI), hyperlocomotion, decrease in gating of hippocampal auditory evoked potentials and robust increase in hippocampal gamma (30-100Hz) oscillations. Similar disruptions were also induced by a single electrographic seizure in the hippocampus. The behavioral and electrophysiological disruptions induced by an NMDA receptor antagonist can be reduced by inactivation or lesion of GABAergic neurons in the medial septum, deep brain stimulation of the medial septum or nucleus accumbens, or positive modulation of GABAB receptors. Our results suggest a close association between high-amplitude hippocampal gamma oscillations and psychosis-relevant behaviors including PPI loss, behavioral hyperactivity and loss in auditory gating. Abnormal electrophysiology suggests a disruption of somatic and apical dendritic inhibition in the hippocampus, resulting in distorted sensory integration, and impaired cognitive and memory processing. The hippocampus is suggested to be a hub in a brain network that participates in psychosis-relevant behaviors, through its direct projection to the nucleus accumbens, or through indirect connections via the entorhinal, cingulate and prefrontal cortices.
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Affiliation(s)
- L Stan Leung
- Department of Physiology and Pharmacology, The University of Western Ontario, London N6A 5C1, Canada.
| | - Jingyi Ma
- Department of Physiology and Pharmacology, The University of Western Ontario, London N6A 5C1, Canada
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Ma J, Leung LS. Involvement of posterior cingulate cortex in ketamine-induced psychosis relevant behaviors in rats. Behav Brain Res 2017; 338:17-27. [PMID: 28993219 DOI: 10.1016/j.bbr.2017.09.051] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2017] [Revised: 09/26/2017] [Accepted: 09/28/2017] [Indexed: 12/16/2022]
Abstract
The involvement of posterior cingulate cortex (PCC) on ketamine-induced psychosis relevant behaviors was investigated in rats. Bilateral infusion of muscimol, a GABAA receptor agonist, into the PCC significantly antagonized ketamine-induced deficit in prepulse inhibition of a startle reflex (PPI), deficit in gating of hippocampal auditory evoked potentials, and behavioral hyperlocomotion in a dose dependent manner. Local infusion of ketamine directly into the PCC also induced a PPI deficit. Systemic injection of ketamine (3mg/kg,s.c.) induced an increase in power of electrographic activity in the gamma band (30-100Hz) in both the PCC and the hippocampus; peak theta (4-10Hz) power was not significantly altered, but peak theta frequency was increased by ketamine. In order to exclude volume conduction from the hippocampus to PCC, inactivation of the hippocampus was made by local infusion of muscimol into the hippocampus prior to ketamine administration. Muscimol in the hippocampus effectively blocked ketamine-induced increase of gamma power in the hippocampus but not in the PCC, suggesting independent generation of gamma waves in PCC and hippocampus. It is suggested that the PCC is part of the brain network mediating ketamine-induced psychosis related behaviors.
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Affiliation(s)
- Jingyi Ma
- Department of Physiology and Pharmacology, The University of Western Ontario, London N6A 5C1, Canada.
| | - L Stan Leung
- Department of Physiology and Pharmacology, The University of Western Ontario, London N6A 5C1, Canada; Graduate Program in Neuroscience, The University of Western Ontario, London N6A 5C1, Canada
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Ma J, Stan Leung L. Effects of GABA-B receptor positive modulator on ketamine-induced psychosis-relevant behaviors and hippocampal electrical activity in freely moving rats. Psychopharmacology (Berl) 2017; 234:3129-3142. [PMID: 28756462 DOI: 10.1007/s00213-017-4705-7] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/17/2016] [Accepted: 07/08/2017] [Indexed: 02/07/2023]
Abstract
RATIONALE Decreased GABAB receptor function is proposed to mediate some symptoms of schizophrenia. OBJECTIVES In this study, we tested the effect of CGP7930, a GABAB receptor positive allosteric modulator, on ketamine-induced psychosis-relevant behaviors and hippocampal electrical activity in behaving rats. METHODS Electrodes were bilaterally implanted into the hippocampus, and cannulae were placed into the lateral ventricles of Long-Evans rats. CGP7930 or vehicle was injected intraperitoneally (i.p.) or intracerebroventricularly (i.c.v.), alone or 15 min prior to ketamine (3 mg/kg, subcutaneous) injection. Paired click auditory evoked potentials in the hippocampus (AEP), prepulse inhibition (PPI), and locomotor activity were recorded before and after drug injection. RESULTS CGP7930 at doses of 1 mg/kg (i.p.) prevented ketamine-induced deficit of PPI. CGP7930 (1 mg/kg i.p.) also prevented the decrease in gating of hippocampal AEP and the increase in hippocampal gamma (65-100 Hz) waves induced by ketamine. Unilateral i.c.v. infusion of CGP7930 (0.3 mM/1 μL) also prevented the decrease in gating of hippocampal AEP induced by ketamine. Ketamine-induced behavioral hyperlocomotion was suppressed by 5 mg/kg i.p. CGP7930. CGP7930 alone, without ketamine, did not significantly affect integrated PPI, locomotion, gating of hippocampal AEP, or gamma waves. CGP7930 (1 mg/kg i.p.) increased heterosynaptically mediated paired pulse depression in the hippocampus, a measure of GABAB receptor function in vivo. CONCLUSIONS CGP7930 reduces the behavioral and electrophysiological disruptions induced by ketamine in animals, and the hippocampus may be one of the neural targets where CGP7930 exerts its actions.
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Affiliation(s)
- Jingyi Ma
- Department of Physiology and Pharmacology, The University of Western Ontario, Medical Sciences Building, London, ON, N6A 5C1, Canada.
| | - L Stan Leung
- Department of Physiology and Pharmacology, The University of Western Ontario, Medical Sciences Building, London, ON, N6A 5C1, Canada.,Graduate Program in Neuroscience, The University of Western Ontario, London, N6A 5C1, Canada
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Leung LS, Jin M, Chu L, Ma J. Positive allosteric modulator of GABAB receptor alters behavioral effects but not afterdischarge progression induced by partial hippocampal kindling. Neuropharmacology 2016; 110:154-164. [DOI: 10.1016/j.neuropharm.2016.07.017] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2016] [Revised: 06/17/2016] [Accepted: 07/15/2016] [Indexed: 12/22/2022]
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Leung LS, Luo T, Ma J, Herrick I. Brain areas that influence general anesthesia. Prog Neurobiol 2014; 122:24-44. [PMID: 25172271 DOI: 10.1016/j.pneurobio.2014.08.001] [Citation(s) in RCA: 90] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2014] [Revised: 08/03/2014] [Accepted: 08/19/2014] [Indexed: 10/24/2022]
Abstract
This document reviews the literature on local brain manipulation of general anesthesia in animals, focusing on behavioral and electrographic effects related to hypnosis or loss of consciousness. Local inactivation or lesion of wake-active areas, such as locus coeruleus, dorsal raphe, pedunculopontine tegmental nucleus, perifornical area, tuberomammillary nucleus, ventral tegmental area and basal forebrain, enhanced general anesthesia. Anesthesia enhancement was shown as a delayed emergence (recovery of righting reflex) from anesthesia or a decrease in the minimal alveolar concentration that induced loss of righting. Local activation of various wake-active areas, including pontis oralis and centromedial thalamus, promoted behavioral or electrographic arousal during maintained anesthesia and facilitated emergence. Lesion of the sleep-active ventrolateral preoptic area resulted in increased wakefulness and decreased isoflurane sensitivity, but only for 6 days after lesion. Inactivation of any structure within limbic circuits involving the medial septum, hippocampus, nucleus accumbens, ventral pallidum, and ventral tegmental area, amygdala, entorhinal and piriform cortex delayed emergence from anesthesia, and often reduced anesthetic-induced behavioral excitation. In summary, the concept that anesthesia works on the sleep-wake system has received strong support from studies that inactivated/lesioned or activated wake-active areas, and weak support from studies that lesioned sleep-active areas. In addition to the conventional wake-sleep areas, limbic structures such as the medial septum, hippocampus and prefrontal cortex are also involved in the behavioral response to general anesthesia. We suggest that hypnosis during general anesthesia may result from disrupting the wake-active neuronal activities in multiple areas and suppressing an atropine-resistant cortical activation associated with movements.
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Affiliation(s)
- L Stan Leung
- Department of Physiology and Pharmacology, The University of Western Ontario, London, Ontario, Canada N6A 5C1.
| | - Tao Luo
- Department of Anesthesiology, Peking University, Shenzhen Hospital, China
| | - Jingyi Ma
- Department of Physiology and Pharmacology, The University of Western Ontario, London, Ontario, Canada N6A 5C1
| | - Ian Herrick
- Department of Anaesthesiology and Perioperative Medicine, The University of Western Ontario, London, Ontario, Canada N6A 5C1
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Pabba M, Wong AYC, Ahlskog N, Hristova E, Biscaro D, Nassrallah W, Ngsee JK, Snyder M, Beique JC, Bergeron R. NMDA receptors are upregulated and trafficked to the plasma membrane after sigma-1 receptor activation in the rat hippocampus. J Neurosci 2014; 34:11325-38. [PMID: 25143613 PMCID: PMC6615506 DOI: 10.1523/jneurosci.0458-14.2014] [Citation(s) in RCA: 92] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2014] [Revised: 07/08/2014] [Accepted: 07/14/2014] [Indexed: 11/21/2022] Open
Abstract
Sigma-1 receptors (σ-1Rs) are endoplasmic reticulum resident chaperone proteins implicated in many physiological and pathological processes in the CNS. A striking feature of σ-1Rs is their ability to interact and modulate a large number of voltage- and ligand-gated ion channels at the plasma membrane. We have reported previously that agonists for σ-1Rs potentiate NMDA receptor (NMDAR) currents, although the mechanism by which this occurs is still unclear. In this study, we show that in vivo administration of the selective σ-1R agonists (+)-SKF 10,047 [2S-(2α,6α,11R*]-1,2,3,4,5,6-hexahydro-6,11-dimethyl-3-(2-propenyl)-2,6-methano-3-benzazocin-8-ol hydrochloride (N-allylnormetazocine) hydrochloride], PRE-084 (2-morpholin-4-ylethyl 1-phenylcyclohexane-1-carboxylate hydrochloride), and (+)-pentazocine increases the expression of GluN2A and GluN2B subunits, as well as postsynaptic density protein 95 in the rat hippocampus. We also demonstrate that σ-1R activation leads to an increased interaction between GluN2 subunits and σ-1Rs and mediates trafficking of NMDARs to the cell surface. These results suggest that σ-1R may play an important role in NMDAR-mediated functions, such as learning and memory. It also opens new avenues for additional studies into a multitude of pathological conditions in which NMDARs are involved, including schizophrenia, dementia, and stroke.
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Affiliation(s)
- Mohan Pabba
- Ottawa Hospital Research Institute, Ottawa, Ontario, Canada, K1H 8M5, and
| | - Adrian Y C Wong
- Ottawa Hospital Research Institute, Ottawa, Ontario, Canada, K1H 8M5, and
| | - Nina Ahlskog
- Ottawa Hospital Research Institute, Ottawa, Ontario, Canada, K1H 8M5, and
| | - Elitza Hristova
- Ottawa Hospital Research Institute, Ottawa, Ontario, Canada, K1H 8M5, and
| | - Dante Biscaro
- Ottawa Hospital Research Institute, Ottawa, Ontario, Canada, K1H 8M5, and
| | - Wissam Nassrallah
- Ottawa Hospital Research Institute, Ottawa, Ontario, Canada, K1H 8M5, and
| | - Johnny K Ngsee
- Department of Cellular and Molecular Medicine, University of Ottawa, Ontario, Canada, K1H 8M5
| | - Melissa Snyder
- Ottawa Hospital Research Institute, Ottawa, Ontario, Canada, K1H 8M5, and
| | - Jean-Claude Beique
- Department of Cellular and Molecular Medicine, University of Ottawa, Ontario, Canada, K1H 8M5
| | - Richard Bergeron
- Ottawa Hospital Research Institute, Ottawa, Ontario, Canada, K1H 8M5, and
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Kiss T, Feng J, Hoffmann W, Shaffer C, Hajós M. Rhythmic theta and delta activity of cortical and hippocampal neuronal networks in genetically or pharmacologically induced N-methyl-d-aspartate receptor hypofunction under urethane anesthesia. Neuroscience 2013; 237:255-67. [DOI: 10.1016/j.neuroscience.2013.01.058] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2012] [Revised: 01/19/2013] [Accepted: 01/22/2013] [Indexed: 10/27/2022]
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Dissanayake DW, Mason R, Marsden CA. Sensory gating, Cannabinoids and Schizophrenia. Neuropharmacology 2013; 67:66-77. [DOI: 10.1016/j.neuropharm.2012.10.011] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2012] [Revised: 10/10/2012] [Accepted: 10/20/2012] [Indexed: 12/12/2022]
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Wildeboer-Andrud KM, Stevens KE. The smoking cessation drug varenicline improves deficient P20-N40 inhibition in DBA/2 mice. Pharmacol Biochem Behav 2011; 100:17-24. [PMID: 21763340 PMCID: PMC3183147 DOI: 10.1016/j.pbb.2011.07.001] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/20/2010] [Revised: 06/30/2011] [Accepted: 07/02/2011] [Indexed: 11/29/2022]
Abstract
Varenicline, an FDA approved smoking cessation pharmacotherapy, is an α4β2* nicotinic acetylcholine receptor (nAChR) partial agonist and an α7* nAChR full agonist. Both subtypes of nAChR are involved in modulating auditory evoked responses in rodents. In DBA/2 mice, an inbred strain, auditory evoked responses to paired auditory stimuli fail to inhibit to the second stimulus. This mouse strain replicates the auditory evoked response inhibition deficit experienced by the majority of schizophrenia patients. In this current study, we examined the effects of five different doses of varenicline (0.06, 0.3, 0.6, 3 and 6mg/kg) on auditory evoked responses in anesthetized DBA/2 mice. We also administered α4β2* and α7* nAChR selective antagonists prior to varenicline administration to determine which nAChR subtypes mediate the effects of varenicline. Four of the five doses of varenicline produced improvements in auditory evoked response inhibition deficits. Selective blockade of either the α4β2* or α7* nAChR in competition with 0.6mg/kg varenicline prevented varenicline induced improvements. In competition with a higher dose of varenicline (3mg/kg) only blockade of the α4β2* nAChR prevented varenicline induced improvement in auditory evoked response inhibition. These data indicate the importance of α4β2* nAChRs and the potential involvement of the α7* subtype in varenicline's effects on auditory evoked responses in DBA/2 mice.
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Kiss T, Hoffmann WE, Scott L, Kawabe TT, Milici AJ, Nilsen EA, Hajós M. Role of Thalamic Projection in NMDA Receptor-Induced Disruption of Cortical Slow Oscillation and Short-Term Plasticity. Front Psychiatry 2011; 2:14. [PMID: 21556284 PMCID: PMC3089990 DOI: 10.3389/fpsyt.2011.00014] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/03/2010] [Accepted: 03/22/2011] [Indexed: 11/13/2022] Open
Abstract
NMDA receptor (NMDAR) antagonists, such as phencyclidine, ketamine, or dizocilpine (MK-801) are commonly used in psychiatric drug discovery in order to model several symptoms of schizophrenia, including psychosis and impairments in working memory. In spite of the widespread use of NMDAR antagonists in preclinical and clinical studies, our understanding of the mode of action of these drugs on brain circuits and neuronal networks is still limited. In the present study spontaneous local field potential (LFP), multi- (MUA) and single-unit activity, and evoked potential, including paired-pulse facilitation (PPF) in response to electrical stimulation of the ipsilateral subiculum were carried out in the medial prefrontal cortex (mPFC) in urethane anesthetized rats. Systemic administration of MK-801 (0.05 mg/kg, i.v.) decreased overall MUA, with a diverse effect on single-unit activity, including increased, decreased, or unchanged firing, and in line with our previous findings shifted delta-frequency power of the LFP and disrupted PPF (Kiss et al., 2011). In order to provide further insight to the mechanisms of action of NMDAR antagonists, MK-801 was administered intracranially into the mPFC and mediodorsal nucleus of the thalamus (MD). Microinjections of MK-801, but not physiological saline, localized into the MD evoked changes in both LFP parameters and PPF similar to the effects of systemically administered MK-801. Local microinjection of MK-801 into the mPFC was without effect on these parameters. Our findings indicate that the primary site of the action of systemic administration of NMDAR antagonists is unlikely to be the cortex. We presume that multiple neuronal networks, involving thalamic nuclei contribute to disrupted behavior and cognition following NMDAR blockade.
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Affiliation(s)
- Tamás Kiss
- Neuroscience Research Unit, Pfizer Global Research and Development, Pfizer Inc . Groton, CT, USA
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Assessment of auditory sensory processing in a neurodevelopmental animal model of schizophrenia--gating of auditory-evoked potentials and prepulse inhibition. Behav Brain Res 2010; 213:142-7. [PMID: 20417666 DOI: 10.1016/j.bbr.2010.04.026] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2010] [Revised: 04/09/2010] [Accepted: 04/15/2010] [Indexed: 12/31/2022]
Abstract
The use of translational approaches to validate animal models is needed for the development of treatments that can effectively alleviate cognitive impairments associated with schizophrenia, which are unsuccessfully treated by the current available therapies. Deficits in pre-attentive stages of sensory information processing seen in schizophrenia patients, can be assessed by highly homologues methods in both humans and rodents, evident by the prepulse inhibition (PPI) of the auditory startle response and the P50 (termed P1 here) suppression paradigms. Treatment with the NMDA receptor antagonist PCP on postnatal days 7, 9, and 11 reliably induce cognitive impairments resembling those presented by schizophrenia patients. Here we evaluate the potential of early postnatal PCP (20mg/kg) treatment in Lister Hooded rats to induce post-pubertal deficits in PPI and changes, such as reduced gating, in the P1 suppression paradigm in the EEG. The results indicate that early postnatal PCP treatment to rats leads to a reduction in PPI of the acoustic startle response. Furthermore, treated animals were assessed in the P1 suppression paradigm and produced significant changes in auditory-evoked potentials (AEP), specifically by an increased P1 amplitude and reduced P2 (P200 in humans) gating. However, the treatment neither disrupted normal P1 gating nor reduced N1 (N100 in humans) amplitude, representing two phenomena that are usually found to be disturbed in schizophrenia. In conclusion, the current findings confirm measures of early information processing to show high resemblance between rodents and humans, and indicate that early postnatal PCP-treated rats show deficits in pre-attentional processing, which are distinct from those observed in schizophrenia patients.
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Dissanayake DW, Zachariou M, Marsden CA, Mason R. Effects of phencyclidine on auditory gating in the rat hippocampus and the medial prefrontal cortex. Brain Res 2009; 1298:153-60. [DOI: 10.1016/j.brainres.2009.08.032] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2008] [Revised: 08/07/2009] [Accepted: 08/07/2009] [Indexed: 10/20/2022]
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16
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Wildeboer KM, Zheng L, Choo KS, Stevens KE. Ondansetron results in improved auditory gating in DBA/2 mice through a cholinergic mechanism. Brain Res 2009; 1300:41-50. [PMID: 19728991 DOI: 10.1016/j.brainres.2009.08.075] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2009] [Revised: 08/14/2009] [Accepted: 08/21/2009] [Indexed: 10/20/2022]
Abstract
The 5-HT(3) receptor antagonist, ondansetron, has been shown to correct the auditory gating deficit in medicated schizophrenia patients. Inhibition of 5-HT(3) receptors releases acetylcholine, the endogenous ligand for nicotinic acetylcholine receptors. The schizophrenia-related auditory gating deficit is modulated, in part, by nicotinic acetylcholine receptors, as is the mouse (DBA/2) model of the deficit. The present study assessed the effects of both acute and chronically administered ondansetron on auditory gating in DBA/2 mice. Auditory gating is defined as a decrease in amplitude of response to the second of a paired identical auditory stimulus presented 0.5 s following an initial auditory stimulus. Acute ondansetron administration at the lowest dose (0.1 mg/kg, IP) tested had no effect, while other doses (0.33 and 1 mg/kg, IP) produced improvements in auditory gating. The improvements were produced through both an increase in response to the first auditory stimulus and a decrease in the response to the second auditory stimulus. Co-administration of an alpha7 nicotinic acetylcholine receptor antagonist, alpha-bungarotoxin, or the alpha4beta2 nicotinic acetylcholine receptor antagonist dihydro-beta-erythroidine, with the 0.33 mg/kg dose of ondansetron blocked the improvement in auditory gating produced by ondansetron alone. There was no difference in response between the chronically injected mice and naive mice. Both showed improved auditory gating, thus, demonstrating no "carry over" effect of daily injections. These data demonstrate that indirect stimulation of nicotinic acetylcholine receptors by ondansetron can improve auditory gating parameters in DBA/2 mice.
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Affiliation(s)
- Kristin M Wildeboer
- Department of Psychiatry, University of Colorado Denver, Mail Stop 8344, RC-1 North, 12800 East 19th Ave. Aurora, CO 80045, USA.
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Inta D, Monyer H, Sprengel R, Meyer-Lindenberg A, Gass P. Mice with genetically altered glutamate receptors as models of schizophrenia: a comprehensive review. Neurosci Biobehav Rev 2009; 34:285-94. [PMID: 19651155 DOI: 10.1016/j.neubiorev.2009.07.010] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2009] [Revised: 07/24/2009] [Accepted: 07/24/2009] [Indexed: 01/28/2023]
Abstract
Recent clinical evidence for the effectiveness of new antipsychotic drugs that specifically target glutamate receptors has rekindled interest in the glutamatergic system regarding pathophysiology and treatment of schizophrenia. The glutamatergic hypothesis of schizophrenia was triggered by the clinical/behavioural observation that NMDA receptor antagonists can induce psychosis in humans and abnormal behaviour with schizophrenia-like symptoms in animals. Initial models focused on NMDA receptor hypofunction as a potential pathogenetic mechanism. More recent genetic and pharmacological studies revealed that malfunction of other components of the glutamatergic system might also be relevant in explaining specific symptoms of this complex disease. Here, we review mutant mouse models with relevance for schizophrenia. These rodent models, in which specific glutamate receptor subtypes or various components of their intracellular transduction machinery are genetically altered, permit a detailed dissection of the contribution of different components of the glutamate system in inducing schizophrenia-like behaviours. They may provide insight into the pathophysiology of schizophrenia and prove useful in the development of new therapeutics.
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Affiliation(s)
- Dragos Inta
- Department of Psychiatry and Psychotherapy, Central Institute of Mental Health, J5, 68159 Mannheim, Germany.
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18
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Dissanayake DWN, Zachariou M, Marsden CA, Mason R. Auditory gating in rat hippocampus and medial prefrontal cortex: effect of the cannabinoid agonist WIN55,212-2. Neuropharmacology 2008; 55:1397-404. [PMID: 18809420 DOI: 10.1016/j.neuropharm.2008.08.039] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2008] [Revised: 06/25/2008] [Accepted: 08/28/2008] [Indexed: 10/21/2022]
Abstract
Sensory gating can be assessed in rodents and humans using an auditory conditioning (C)-test (T) paradigm, with schizophrenic patients exhibiting a loss of gating. Dysregulation of the endocannabinoid system has been proposed to be involved in the pathogenesis of schizophrenia. We studied auditory gating and the effects of the cannabinoid agonist WIN55,212-22 on gating in CA3 and dentate gyrus (DG) of the hippocampus and medial prefrontal cortex (mPFC) in male Lister hooded rats using in vivo electrophysiology. The effects of a single dose of WIN55,212-2 on the N2 local field potential (LFP) test/conditioning amplitude ratios (T/C ratio) and response latencies were examined. In rats that demonstrated gating of N2, mPFC showed higher T/C ratios and shorter conditioning response latencies compared to DG and CA3. WIN55,212-2 disrupted auditory gating in all three areas with a significant increase in test amplitudes in the gating rats. A group of non-gating rats demonstrated higher test amplitudes and higher T/C ratios compared to gating rats. WIN55,212-2 had no effect on T/C ratios in the non-gating rats. The cannabinoid receptor (CB1) antagonist SR141716A prevented WIN55,212-2 induced disruption of gating. This study demonstrates gated auditory-evoked responses in CA3, DG and mPFC. The mPFC showed an early phase of gating which may later be modulated by CA3 and DG activity. Furthermore, cannabinoid receptor activation disrupted auditory gating in CA3, DG and mPFC, an effect which was prevented by CB1 receptor antagonism. The results further demonstrate the presence of a non-gating rat population which responded differently to cannabinoid agonists.
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Affiliation(s)
- Dilshani W N Dissanayake
- School of Biomedical Sciences, Medical School, Queen's Medical Centre, University of Nottingham, Nottingham, Nottinghamshire NG7 2UH, UK.
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19
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Stevens KE, Adams CE, Mellott TJ, Robbins E, Kisley MA. Perinatal choline deficiency produces abnormal sensory inhibition in Sprague-Dawley rats. Brain Res 2008; 1237:84-90. [PMID: 18778692 DOI: 10.1016/j.brainres.2008.08.047] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2008] [Revised: 08/14/2008] [Accepted: 08/15/2008] [Indexed: 10/21/2022]
Abstract
Adequate choline levels in rodents during gestation have been shown to be critical to several functions, including certain learning and memory functions, when tested at adulthood. Choline is a selective agonist for the alpha7 nicotinic receptor which appears in development before acetylcholine is present. Normal sensory inhibition is dependent, in part, upon sufficient numbers of this receptor in the hippocampus. The present study assessed sensory inhibition in Sprague-Dawley rats gestated on normal (1.1 g/kg), deficient (0 g/kg) or supplemented (5 g/kg) choline in the maternal diet during the critical period for cholinergic cell development (E12-18). Rats gestated on deficient choline showed abnormal sensory inhibition when tested at adulthood, while rats gestated on normal or supplemented choline showed normal sensory inhibition. Assessment of hippocampal alpha-bungarotoxin to visualize nicotinic alpha7 receptors revealed no difference between the gestational choline levels. These data suggest that attention to maternal choline levels for human pregnancy may be important to the normal functioning of the offspring.
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Affiliation(s)
- Karen E Stevens
- Medical Research Service, Department of Veterans Affairs Medical Center, Denver, CO, USA.
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20
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Simosky JK, Freedman R, Stevens KE. Olanzapine improves deficient sensory inhibition in DBA/2 mice. Brain Res 2008; 1233:129-36. [PMID: 18687314 DOI: 10.1016/j.brainres.2008.07.057] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2008] [Revised: 07/10/2008] [Accepted: 07/11/2008] [Indexed: 10/21/2022]
Abstract
Most schizophrenia patients do not inhibit their P50 auditory evoked potential to the second of duplicate auditory stimuli, reflecting a failure to inhibit responses to irrelevant sensory input. Typical antipsychotic drugs do not improve this deficit while some atypical antipsychotics do. A previous study using an animal model, deficient P20-N40 (which corresponds to the human P50) inhibitory processing in DBA/2 mice found that sensory inhibition was improved by clozapine, the prototypical atypical antipsychotic, but not by haloperidol, a typical antipsychotic. The improvement after clozapine was mediated by alpha7 nicotinic receptors. The present study addresses whether another atypical antipsychotic, olanzapine, will also improve sensory inhibition deficits in the mouse model. In vivo electrophysiological recordings of the P20-N40 auditory evoked potential in anesthetized DBA/2 mice, which spontaneously exhibit a schizophrenia-like inhibitory processing deficit, were obtained after olanzapine alone (0.01, 0.033, 0.1, 0.33 mg/kg, IP) and the efficacious dose of olanzapine (0.033 mg/kg, IP) in combination with either the alpha7 nicotinic receptor antagonist alpha-bungarotoxin or the alpha4beta2 nicotinic receptor antagonist di-hydro-beta-erythroidine. All doses of olanzapine produced improved P20-N40 inhibitory processing in DBA/2 mice. The normalization observed after the 0.033 mg/kg dose of olanzapine was due to a selective decrease in response to the second auditory stimulus indicating an increase in inhibitory processing. This improvement was blocked by pre-administration of alpha-bungarotoxin but not di-hydro-beta-erythroidine. Like clozapine, olanzapine acts via alpha7 nicotinic receptors to elicit improved inhibitory processing of auditory stimuli.
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Affiliation(s)
- Johanna K Simosky
- Department of Pharmacology, University of Colorado Health Sciences Center, Denver, Colorado, USA
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21
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Wildeboer KM, Stevens KE. Stimulation of the alpha4beta2 nicotinic receptor by 5-I A-85380 improves auditory gating in DBA/2 mice. Brain Res 2008; 1224:29-36. [PMID: 18582447 DOI: 10.1016/j.brainres.2008.06.007] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2008] [Revised: 06/03/2008] [Accepted: 06/04/2008] [Indexed: 11/17/2022]
Abstract
Abnormal auditory gating is a symptom of schizophrenia which has been proposed to be mediated through the alpha7 nicotinic acetylcholine receptor (nAChR). It has been shown that the non-selective nicotinic agonist nicotine has an influence on auditory gating in part by acting on the alpha4beta2 nAChR. The goal of this study was to determine the effect of 5-I A-85380, an agonist for the alpha4beta2 nAChR, in an inbred mouse model with a deficiency for auditory gating. Anesthetized DBA/2 mice were administered 5-I A-85380 alone and in combination with the alpha4beta2 nAChR antagonist, dihydro-beta-erythroidine, or the alpha7 nAChR antagonist, alpha-bungarotoxin. A recording electrode in the CA3 region of the hippocampus recorded P20-N40 waveforms in response to two auditory stimuli. The amplitudes of the response to the first and second clicks were used to determine TC ratios, the measure of auditory gating. 5-I A-85380 significantly decreased the TC ratios by selectively increasing the response amplitudes to the first click with no significant influence on the response amplitudes to the second click. The effect was blocked by dihydro-beta-erythroidine whereas alpha-bungarotoxin had no effect on response amplitude to either click. Although the alpha7 nAChR may mediate the hippocampal response of DBA/2 mice to the second click, the alpha4beta2 nAChR appears to modulate the response to the first click. Thus, the present study implicates the involvement of more than one subtype of nAChR in the auditory gating of DBA/2 mice, specifically the alpha4beta2 nAChR, and its role in the response amplitude to the first stimulus.
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Affiliation(s)
- Kristin M Wildeboer
- Department of Psychiatry, University of Colorado Denver, Aurora, CO 80045, USA.
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22
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Zachariou M, Dissanayake DWN, Coombes S, Owen MR, Mason R. Sensory gating and its modulation by cannabinoids: electrophysiological, computational and mathematical analysis. Cogn Neurodyn 2008; 2:159-70. [PMID: 19003482 PMCID: PMC2427066 DOI: 10.1007/s11571-008-9050-4] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2008] [Accepted: 04/06/2008] [Indexed: 11/10/2022] Open
Abstract
Gating of sensory information can be assessed using an auditory conditioning-test paradigm which measures the reduction in the auditory evoked response to a test stimulus following an initial conditioning stimulus. Recording brainwaves from specific areas of the brain using multiple electrodes is helpful in the study of the neurobiology of sensory gating. In this paper, we use such technology to investigate the role of cannabinoids in sensory gating in the CA3 region of the rat hippocampus. Our experimental results show that application of the exogenous cannabinoid agonist WIN55,212-2 can abolish sensory gating. We have developed a phenomenological model of cannabinoid dynamics incorporated within a spiking neural network model of CA3 with synaptically interacting pyramidal and basket cells. Direct numerical simulations of this model suggest that the basic mechanism for this effect can be traced to the suppression of inhibition of slow GABA(B) synapses. Furthermore, by working with a simpler mathematical firing rate model we are able to show the robustness of this mechanism for the abolition of sensory gating.
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Affiliation(s)
- Margarita Zachariou
- School of Mathematical Sciences, University of Nottingham, Nottingham, NG7 2RD, UK,
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23
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Bickel S, Lipp HP, Umbricht D. Early auditory sensory processing deficits in mouse mutants with reduced NMDA receptor function. Neuropsychopharmacology 2008; 33:1680-9. [PMID: 17712349 DOI: 10.1038/sj.npp.1301536] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Cognitive deficits in schizophrenia include impairments at automatic, preattentive stages of sensory information processing. These deficits are evident in the prepulse inhibition- (PPI) and habituation of the auditory startle response paradigm, the paired tone paradigm in the EEG, and the peak recovery function of auditory evoked potentials (AEP). Administration of NMDA receptor antagonists reliably disrupts PPI and habituation of the startle, but not gating of AEPs in rodents. In the peak recovery paradigm, patients with schizophrenia and primates treated with NMDA receptor antagonists show reduced maximal response at long interstimulus intervals (ISI), but normal responses at short ISIs. Thus reduced NMDA receptor signalling may underlie alterations in these paradigms observed in schizophrenia. We tested the paradigms mentioned in mouse mutants with reduced expression of the NR1 subunit of the NMDA receptor (N = 15) and their wild-type littermates (N = 16). The NR1 mutant mice showed impaired habituation and PPI of the auditory startle response, as well as impaired gating in the paired tone paradigm. Deficits between the two gating measures did not correlate, corroborating previous evidence that these paradigms measure distinct processes. In the peak recovery paradigm, the NR1 mutants showed increased responses of the AEPs P1 and N1 at short ISIs but no difference between groups were observed at long ISIs. In conclusion, the NR1 hypomorphic mice modelled sensory and sensorimotor gating and startle habituation deficits observed in schizophrenia, but failed to model alterations in the peak recovery function.
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Affiliation(s)
- Stephan Bickel
- Department of Neuroanatomy, Institute of Anatomy, University of Zurich, Zurich, Switzerland.
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Cromwell HC, Woodward DJ. Inhibitory gating of single unit activity in amygdala: effects of ketamine, haloperidol, or nicotine. Biol Psychiatry 2007; 61:880-9. [PMID: 17054921 DOI: 10.1016/j.biopsych.2006.06.037] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/22/2006] [Revised: 05/26/2006] [Accepted: 06/27/2006] [Indexed: 11/18/2022]
Abstract
BACKGROUND Inhibitory gating is thought to be a basic process for filtering incoming stimuli to the brain. Little information is currently available concerning local neural networks of inhibitory gating or the intrinsic neurochemical substrates involved in the process. METHODS The goal of the present study was to examine the pharmacological aspects of inhibitory gating from single units in the amygdala. We tested the effects of ketamine (80 mg/kg) and haloperidol (1 mg/kg) on inhibitory gating. Additionally, we examined the effect of nicotine (1.2 mg/kg) on single unit gating in this same brain structure. RESULTS We found that in one subset of neurons, ketamine administration significantly reduced tone responsiveness with a subsequent loss of inhibitory gating, whereas the other subset persisted in both auditory responding and gating albeit at a weaker level. Haloperidol and nicotine had very similar effects, exemplified by a dramatic increase in the response to the initial "conditioning" tone with a subsequent improvement in inhibitory gating. CONCLUSIONS Tone responsiveness and inhibitory gating persists in a subset of neurons after glutamate N-methyl-D-aspartate receptor blockade. Dopamine and nicotine modulate gating in these normal animals and have similar effects of enhancing responsiveness to auditory stimulation at the single unit and evoked potential level.
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Affiliation(s)
- Howard C Cromwell
- Department of Physiology and Pharmacology, School of Medicine, Wake Forest University, Winston-Salem, North Carolina, USA.
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25
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Swerdlow NR, Geyer MA, Shoemaker JM, Light GA, Braff DL, Stevens KE, Sharp R, Breier M, Neary A, Auerbach PP. Convergence and divergence in the neurochemical regulation of prepulse inhibition of startle and N40 suppression in rats. Neuropsychopharmacology 2006; 31:506-15. [PMID: 16123772 PMCID: PMC1373667 DOI: 10.1038/sj.npp.1300841] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Prepulse inhibition of startle ('PPI'), a cross-species measure of sensorimotor gating, is impaired in schizophrenia patients. Suppression of P50 event-related potentials (ERPs) in response to the second of two clicks ('P50 gating') is also impaired in schizophrenia. Suppression of N40 ERPs to the second of two clicks ('N40 gating') is thought by some to be a rat homolog of human P50 gating. Emerging evidence suggests differences in the neurobiology of deficits detected by PPI vs P50 (or N40) gating. We recorded PPI and N40 gating contemporaneously in rats, to assess convergence and divergence in the neurochemical regulation of these measures. Dose-response studies examined the effects of apomorphine (APO), phencyclidine (PCP) or the 5HT2A agonist DOI on PPI, and on motor responses to stimuli (S1 and S2) that elicit N40 gating. Effects of optimal drug doses on PPI and N40 gating were then assessed in other rats with implanted cortical surface electrodes. APO, PCP and DOI caused dose-dependent disruptions of both PPI and gating of motor responses to N40 stimuli. Reduced PPI reflected diminished prepulse effectiveness, demonstrated by increased startle levels on prepulse+pulse trials. In contrast, reduced gating of motor responses to N40 stimuli reflected a reduced motor response to S1. In separate rats, robust PPI, N40 potentials and N40 gating could be detected within one test. PPI and N40 gating were disrupted by APO, PCP, and DOI. Again, drug effects on PPI reflected increased startle on prepulse+pulse trials, while those on N40 gating reflected reduced ERP responses to S1. In conclusion, when PPI and N40 gating were studied concurrently in rats, drug effects on PPI reflected reduced inhibition of startle by the prepulse, while diminished N40 gating reflected S1 response suppression. Despite similarities in drug sensitivity, these results suggest that distinct neurobiological mechanisms underlie drug-induced deficits in PPI and N40 gating.
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Affiliation(s)
- Neal R Swerdlow
- Department of Psychiatry, UCSD School of Medicine, La Jolla, CA 92093-0804, USA.
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26
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Miller CL, Llenos IC, Dulay JR, Weis S. Upregulation of the initiating step of the kynurenine pathway in postmortem anterior cingulate cortex from individuals with schizophrenia and bipolar disorder. Brain Res 2006; 1073-1074:25-37. [PMID: 16448631 DOI: 10.1016/j.brainres.2005.12.056] [Citation(s) in RCA: 181] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2005] [Revised: 11/22/2005] [Accepted: 12/11/2005] [Indexed: 11/27/2022]
Abstract
Upregulation of the kynurenine pathway has been associated with several etiologies of psychosis, an indication that increased levels of pathway intermediates might be involved in eliciting some psychotic features. In schizophrenia, tryptophan 2,3-dioxygenase (TDO2) was previously identified in postmortem frontal cortex as the enzyme likely responsible for the reported increase in pathway activity in the brain. For this follow-up study of postmortem anterior cingulate gyrus, we have found evidence of increased TDO2 activity in schizophrenia at three different levels of regulation: mRNA, protein, and metabolic product. The results were unaffected by neuroleptic status or smoking history. To make the distinction between mental disorders with psychosis and those without, this study included patients with bipolar disorder and major depression. Compared to the control group, the HPLC, RT-PCR, and immunohistochemistry results show significant elevation of (1) kynurenine in schizophrenia (1.9-fold, P = 0.02), and in bipolar disorder (1.8-fold, P = 0.04), primarily in the bipolar subgroup with psychosis (2.1-fold, P = 0.03); (2) TDO2 mRNA in schizophrenia (1.7-fold; P = 0.049); and (3) the immunohistochemistry values for the density of TDO2-positive white matter glial cells in schizophrenia (P = 0.01) and in major depression (P = 0.03) as well as the density and intensity of glial cells (in both gray and white matter) stained for TDO2 in bipolar disorder (P = 0.02). Unlike the results for schizophrenia and bipolar disorder, the increase in TDO2 protein in the major depression group was not associated with an increase in kynurenine concentration.
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Affiliation(s)
- Christine L Miller
- Stanley Division of Developmental Neurovirology, Department of Pediatrics, Johns Hopkins University, 600 N. Wolfe St./Blalock 1105, Baltimore, MD 21287, USA.
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27
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Hashimoto K, Iyo M, Freedman R, Stevens KE. Tropisetron improves deficient inhibitory auditory processing in DBA/2 mice: role of alpha 7 nicotinic acetylcholine receptors. Psychopharmacology (Berl) 2005; 183:13-9. [PMID: 16136299 DOI: 10.1007/s00213-005-0142-0] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/29/2004] [Accepted: 07/17/2005] [Indexed: 11/25/2022]
Abstract
RATIONALE Deficient inhibitory processing of the P50 auditory evoked potential is a pathophysiological feature of schizophrenia. Several lines of evidence suggest that alpha 7 nicotinic receptors play a critical role in this phenomenon. Similar to schizophrenic patients, DBA/2 mice spontaneously exhibit a deficit in inhibitory processing of the P20-N40 auditory evoked potential, which is thought to be a rodent analog of the human P50 auditory evoked potential. OBJECTIVE The present study was undertaken to examine whether tropisetron, a partial agonist at alpha 7 nicotinic receptors and an antagonist at 5-hydroxytryptamine-3 receptors, improves this deficit in DBA/2 mice. RESULTS Administration of tropisetron (1 mg/kg i.p.) significantly improved the deficient inhibitory processing of the P20-N40 auditory evoked potential in DBA/2 mice. Coadministration of methyllycaconitine (MLA; 3 mg/kg i.p.), a partially selective antagonist at alpha 7 nicotinic receptors, significantly blocked the normalizing effect of tropisetron. Furthermore, MLA alone did not alter the deficient inhibitory processing of the P20-N40 auditory evoked potential in DBA/2 mice. CONCLUSIONS The data suggest that tropisetron improves the deficient inhibitory processing of the P20-N40 auditory evoked potential in DBA/2 mice by effects on alpha 7 and perhaps alpha 4 beta 2 nicotinic receptors. Tropisetron may be useful for the treatment of deficient inhibitory processing in schizophrenia.
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Affiliation(s)
- Kenji Hashimoto
- Division of Clinical Neuroscience, Chiba University Center for Forensic Mental Health, 1-8-1 Inohana, Chiba, Chiba 260-8670, Japan.
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28
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Joy B, McMahon RP, Shepard PD. Effects of acute and chronic clozapine on D-amphetamine-induced disruption of auditory gating in the rat. Psychopharmacology (Berl) 2004; 174:274-82. [PMID: 14726994 DOI: 10.1007/s00213-003-1731-4] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
RATIONALE Auditory gating deficits observed in patients with schizophrenia have been modeled in animals administered the indirect-acting monoaminergic agonist, D-amphetamine (AMPH). The atypical antipsychotic drug clozapine (CLOZ) reverses the disruption of auditory gating in schizophrenic patients. However, its effects on psychostimulant-induced deficits in animals have yet to be assessed. OBJECTIVES In the present series of experiments, an auditory evoked potential paradigm was used to: (a) confirm the ability of AMPH to alter auditory gating in the anesthetized rat, (b) specify the nature of the accompanying change(s) in evoked potential waveforms and (c) determine the effects of CLOZ administration on AMPH-induced alterations in auditory gating. METHODS We compared the effects of acute (5 mg/kg, i.p.) and chronic (28 days, 0.5 mg/ml in drinking water) CLOZ on AMPH-induced (1.8 mg/kg, i.p.) alterations in evoked potentials recorded in the hippocampus of anesthetized rats during presentation of a pair of identical tones. Gating was assessed by comparing the amplitude of conditioning and test responses in CLOZ and AMPH-treated rats. RESULTS The ratio of test to conditioning response amplitude (T/C ratio) was not altered by vehicle or CLOZ alone. However, T/C ratio was significantly increased following AMPH due to suppression of the conditioning response. Acute but not chronic CLOZ attenuated but did not prevent the increase in T/C ratio. CONCLUSIONS Qualitative differences between the idiopathic gating deficits observed in schizophrenic patients and AMPH-induced increases in T/C ratio in animals limit this models utility as a means of evaluating the ability of atypical antipsychotic drugs to restore normal sensory gating.
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Affiliation(s)
- Brian Joy
- Maryland Psychiatric Research Center, University of Maryland School of Medicine, P.O. Box 21247, Baltimore, MD 21228, USA
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Abstract
AbstractN-methyl-d-aspartate receptor (NMDAR) dysfunction plays a crucial role in schizophrenia, leading to impairments in cognitive coordination. NMDAR agonists (e.g., glycine) ameliorate negative and cognitive symptoms, consistent with NMDAR models. However, not all types of cognitive coordination use NMDAR. Further, not all aspects of cognitive coordination are impaired in schizophrenia, suggesting the need for specificity in applying the cognitive coordination construct.
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Abstract
AbstractPhillips & Silverstein's focus on schizophrenia as a failure of “cognitive coordination” is welcome. They note that a simple hypothesis of reduced Gamma synchronisation subserving impaired coordination does not fully account for recent observations. We suggest that schizophrenia reflects a dynamic compensation to a core deficit of coordination, expressed either as hyper- or hyposynchronisation, with neurotransmitter systems and arousal as modulatory mechanisms.
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Abstract
AbstractNumerous searches have failed to identify a single co-occurrence of total blindness and schizophrenia. Evidence that blindness causes loss of certain NMDA-receptor functions is balanced by reports of compensatory gains. Connections between visual and anterior cingulate NMDA-receptor systems may help to explain how blindness could protect against schizophrenia.
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32
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Setting domain boundaries for convergence of biological and psychological perspectives on cognitive coordination in schizophrenia. Behav Brain Sci 2003. [DOI: 10.1017/s0140525x0328002x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
AbstractThe claim that the disorganized subtype of schizophrenia results from glutamate hypofunction is enhanced by consideration of current subtypology of schizophrenia, symptom definition, interdependence of neurotransmitters, and the nature of the data needed to support the hypothesis. Careful specification clarifies the clinical reality of disorganization as a feature of schizophrenia and increases the utility of the subtype.
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Abstract
AbstractAlthough context-processing deficits may be core features of schizophrenia, context remains a poorly defined concept. To test Phillips & Silverstein's model, we need to operationalize context more precisely. We offer several useful ways of framing context and discuss enhancing or facilitating schizophrenic patients' performance under different contextual situations. Furthermore, creativity may be a byproduct of cognitive uncoordination.
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Abstract
AbstractImpairments in cognitive coordination in schizophrenia are supported by phenomenological data that suggest deficits in the processing of visual context. Although the target article is sympathetic to such a phenomenological perspective, we argue that the relevance of phenomenological data for a wider understanding of consciousness in schizophrenia is not sufficiently addressed by the authors.
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Guarding against over-inclusive notions of “context”: Psycholinguistic and electrophysiological studies of specific context functions in schizophrenia. Behav Brain Sci 2003. [DOI: 10.1017/s0140525x03470027] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
AbstractPhillips & Silverstein offer an exciting synthesis of ongoing efforts to link the clinical and cognitive manifestations of schizophrenia with cellular accounts of its pathophysiology. We applaud their efforts but wonder whether the highly inclusive notion of “context” adequately captures some important details regarding schizophrenia and NMDA/glutamate function that are suggested by work on language processing and cognitive electrophysiology.
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Abstract
AbstractMechanisms that contribute to perceptual processing dysfunction in schizophrenia were examined by Phillips & Silverstein, and formulated as involving disruptions in both local and higher-level coordination of signals. We agree that dysfunction in the coordination of cognitive functions (disconnection) is also indicated for many of the linguistic processing deficits documented for schizophrenia. We suggest, however, that it may be necessary to add a timing mechanism to the theoretical account.
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Abstract
AbstractSchizophrenics exhibit a deficit in theory of mind (ToM), but an intact theory of biology (ToB). One explanation is that ToM relies on an independent module that is selectively damaged. Phillips & Silverstein's analyses suggest an alternative: ToM requires the type of coordination that is impaired in schizophrenia, whereas ToB is spared because this type of coordination is not involved.
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Abstract
AbstractThe additional arguments and evidence supplied by the commentaries strengthen the hypothesis that underactivity of NMDA receptors produces impaired cognitive coordination in schizophrenia. This encourages the hope that though the distance from molecules to mind is great, it can nevertheless be traversed. We therefore predict that in this decade or the next molecular psychology will be seen to be as fundamental to our understanding of mind as molecular biology is to our understanding of life.
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Abstract
AbstractIt is proposed that cortical activity is normally coordinated across synaptically connected areas and that this coordination supports cognitive coherence relations. This view is consistent with the NMDA- hypoactivity hypothesis of the target article in regarding disorganization symptoms in schizophrenia as arising from disruption of normal interareal coordination. This disruption may produce abnormal contextual effects in the cortex that lead to anomalous cognitive coherence relations.
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Abstract
AbstractThis commentary compares clinical aspects of ketamine with the amphetamine model of schizophrenia. Hallucinations and loss of insight, associated with amphetamine, seem more schizophrenia-like. Flat affect encountered with ketamine is closer to the clinical presentation in schizophrenia. We argue that flat affect is not a sign of schizophrenia, but rather, arisk factorfor chronic schizophrenia.
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Cortical connectivity in high-frequency beta-rhythm in schizophrenics with positive and negative symptoms. Behav Brain Sci 2003. [DOI: 10.1017/s0140525x03440028] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
AbstractIn chronic schizophrenic patients with both positive and negative symptoms (see Table 1), interhemispheric connections at the high frequency beta2-rhythm are absent during cognitive tasks, in contrast to normal controls, who have many interhemispheric connections at this frequency in the same situation. Connectivity is a fundamental brain feature, evidently greatly promoted by the NMDA system. It is a more reliable measure of brain function than the spectral power of this rhythm.
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Shepard PD, Joy B, Clerkin L, Schwarcz R. Micromolar brain levels of kynurenic acid are associated with a disruption of auditory sensory gating in the rat. Neuropsychopharmacology 2003; 28:1454-62. [PMID: 12700696 DOI: 10.1038/sj.npp.1300188] [Citation(s) in RCA: 110] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Brain levels of kynurenic acid (KYNA), an endogenous antagonist of glycine(B)/NMDA and alpha-7 nicotinic acetylcholine receptors, are elevated in individuals with schizophrenia. Both receptors are broadly implicated in the pathophysiology of this disease, particularly in the deficits many patients show in filtering the sensorium. In the present study, we sought to determine whether elevated brain levels of KYNA disrupt auditory gating in anesthetized rats. A mid-latency evoked potential was recorded from the hippocampus in response to a pair of auditory tones. Gating was assessed by determining the ratio of the amplitude of test and conditioning responses (T/C ratio) in rats that had received KYNA's precursor L-kynurenine (KYN; 150 mg/kg, i.p.) together with probenecid (PBCD; 200 mg/kg, i.p.) 2 h prior to the start of the recording session. KYNA levels in the hippocampus of KYN+PBCD-treated rats were increased 500-fold, and accompanied by a significant increase in T/C ratio consistent with a disruption in sensory gating. PBCD alone increased hippocampal KYNA 12-fold, but did not significantly elevate T/C ratio. L-701,324 (3-30 mg/kg, i.v.), a centrally acting glycine(B) site antagonist, also failed to disrupt gating; however, large quantities of the competitive NMDA receptor antagonist DL-2-amino-5-phosphopentanoate (200 nmol, i.c.v.) markedly increased T/C ratio. Thus, while total blockade of NMDA receptors disrupts auditory gating, partial blockade achieved by antagonism of its glycine coagonist binding site does not. These observations indicate that the disruption in auditory processing in rats with greatly elevated KYNA levels is not attributable to the compound's antagonist actions at the glycine(B) receptor.
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Affiliation(s)
- Paul D Shepard
- Maryland Psychiatric Research Center, Department of Psychiatry, University of Maryland School of Medicine, PO Box 21247, Baltimore, MD 21228, USA.
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Huang MX, Edgar JC, Thoma RJ, Hanlon FM, Moses SN, Lee RR, Paulson KM, Weisend MP, Irwin JG, Bustillo JR, Adler LE, Miller GA, Canive JM. Predicting EEG responses using MEG sources in superior temporal gyrus reveals source asynchrony in patients with schizophrenia. Clin Neurophysiol 2003; 114:835-50. [PMID: 12738429 DOI: 10.1016/s1388-2457(03)00041-5] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
OBJECTIVE An integrated analysis using Electroencephalography (EEG) and magnetoencephalography (MEG) is introduced to study abnormalities in early cortical responses to auditory stimuli in schizophrenia. METHODS Auditory responses were recorded simultaneously using EEG and MEG from 20 patients with schizophrenia and 19 control subjects. Bilateral superior temporal gyrus (STG) sources and their time courses were obtained using MEG for the 30-100 ms post-stimulus interval. The MEG STG source time courses were used to predict the EEG signal at electrode Cz. RESULTS In control subjects, the STG sources predicted the EEG Cz recording very well (97% variance explained). In schizophrenia patients, the STG sources accounted for substantially (86%) and significantly (P<0.0002) less variance. After MEG-derived STG activity was removed from the EEG Cz signal, the residual signal was dominated by 40 Hz activity, an indication that the remaining variance in EEG is probably contributed by other brain generators, rather than by random noise. CONCLUSIONS Integrated MEG and EEG analysis can differentiate patients and controls, and suggests a basis for a well established abnormality in the cortical auditory response in schizophrenia, implicating a disorder of functional connectivity in the relationship between STG sources and other brain generators.
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Affiliation(s)
- M X Huang
- Center for Functional Brain Imaging, New Mexico VA Health Care System, Building 49 (114M), 1501 San Pedro Drive, SE, Albuquerque 87108, USA.
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Where the rubber meets the road: The importance of implementation. Behav Brain Sci 2003. [DOI: 10.1017/s0140525x03230028] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
AbstractPhillips & Silverstein argue that a range of cognitive disturbances in schizophrenia result from a deficit in cognitive coordination attributable to NMDA receptor dysfunction. We suggest that the viability of this hypothesis would be further supported by explicit implementation in a computational framework that can produce quantitative estimates of the behavior of both healthy individuals and individuals with schizophrenia.
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Context, connection, and coordination: The need to switch. Behav Brain Sci 2003. [DOI: 10.1017/s0140525x03370025] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
AbstractContext, connection, and coordination (CCC) describe well where the problems that apply to thought-disordered patients with schizophrenia lie. But they may be part of the experience of those with other symptom constellations. Switching is an important mechanism to allow context to be applied appropriately to changing circumstances. In some cases, NMDA-voltage modulations may be central, but gain and shift are also functions that monoaminergic systems express in CCC.
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Synchronous dynamics for cognitive coordination: But how? Behav Brain Sci 2003. [DOI: 10.1017/s0140525x03450024] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
AbstractAlthough interesting, the hypotheses proposed by Phillips & Silverstein lack unifying structure both in specific mechanisms and in cited evidence. They provide little to support the notion that low-level sensory processing and high-level cognitive coordination share dynamic grouping by synchrony as a common processing mechanism. We suggest that more realistic large-scale modeling at multiple levels is needed to address these issues.
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A wide-spectrum coordination model of schizophrenia. Behav Brain Sci 2003. [DOI: 10.1017/s0140525x03240024] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
AbstractThe target article presents a model for schizophrenia extending four levels of abstraction: molecules, cells, cognition, and syndrome. An important notion in the model is that of coordination, applicable to both the level of cells and of cognition. The molecular level provides an “implementation” of the coordination at the cellular level, which in turn underlies the coordination at the cognitive level, giving rise to the clinical symptoms.
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Abstract
AbstractTo understand schizophrenia, a linking hypothesis is needed that shows how brain mechanisms lead to behavioral functions in normals, and also how breakdowns in these mechanisms lead to behavioral symptoms of schizophrenia. Such a linking hypothesis is now available that complements the discussion offered by Phillips & Silverstein (P&S).
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Spatial integration in perception and cognition: An empirical approach to the pathophysiology of schizophrenia. Behav Brain Sci 2003. [DOI: 10.1017/s0140525x03260027] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
AbstractEvidence for a dysfunction in cognitive coordination in schizophrenia is emerging, but it is not specific enough to prove (or disprove) this long-standing hypothesis. Many aspects of the external world are spatially mapped in the brain. A comprehensive internal representation relies on integration of information across space. Focus on spatial integration in the perceptual and cognitive processes will generate empirical data that shed light on the pathophysiology of schizophrenia.
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Krause M, Hoffmann WE, Hajós M. Auditory sensory gating in hippocampus and reticular thalamic neurons in anesthetized rats. Biol Psychiatry 2003; 53:244-53. [PMID: 12559658 DOI: 10.1016/s0006-3223(02)01463-4] [Citation(s) in RCA: 99] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
BACKGROUND Auditory gating is thought to reflect sensory information processing and is absent or diminished in schizophrenic patients. Although abnormal thalamic sensory processing has been proposed in schizophrenia, sensory gating of thalamic neurons has not been demonstrated experimentally. The aim of the present study was to establish whether auditory gating is present in the rat thalamus using a well-characterized animal model of auditory gating and schizophrenia. METHODS Hippocampal electroencephalogram and single-unit activity in the thalamic reticular nucleus (nRT) were recorded in anaesthetized rats. Evoked potentials in the hippocampus and neuronal activity in the nRT were monitored in response to bilateral auditory stimuli. The effects of the psychostimulant D-amphetamine and the antipsychotic haloperidol on auditory gating were evaluated. RESULTS Thalamic reticular nucleus neurons showed gated responses to paired-tone auditory stimuli, resembling hippocampal auditory gating. D-amphetamine disrupted auditory gating of nRT neurons and abolished their burst activity. D-amphetamine also disrupted hippocampal auditory gating and induced hippocampal theta activity. The amphetamine-induced gating deficit was reversed by haloperidol in both regions. CONCLUSIONS Our findings provide the first experimental evidence for auditory gating of nRT neurons. We demonstrated that amphetamine disrupts sensory processing of nRT neurons, indicating similarities between hippocampal and thalamic sensory gating. These findings support the presumed connection between dopamine hyperfunction and abnormal thalamic filtering in schizophrenia.
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Affiliation(s)
- Michael Krause
- Pharmacia Corporation, Neurobiology, 301 Henrietta Street, Kalamazoo, Michigan 49007, USA
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