1
|
Decreased dopamine in striatum and difficult locomotor recovery from MPTP insult after exposure to radiofrequency electromagnetic fields. Sci Rep 2019; 9:1201. [PMID: 30718744 PMCID: PMC6362053 DOI: 10.1038/s41598-018-37874-z] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2018] [Accepted: 12/12/2018] [Indexed: 12/23/2022] Open
Abstract
Concern is growing about possible neuronal effects of human exposure to radiofrequency electromagnetic fields because of the increasing usage of cell phones and the close proximity of these devices to the brain when in use. We found that exposure to a radiofrequency electromagnetic field (RF-EMF) of 835 MHz (4.0 W/kg specific absorption rate [SAR] for 5 h/day for 12 weeks) affects striatal neurons in C57BL/6 mice. The number of synaptic vesicles (SVs) in striatal presynaptic boutons was significantly decreased after RF-EMF exposure. The expression levels of synapsin I and II were also significantly decreased in the striatum of the RF-EMF-exposed group. RF-EMF exposure led to a reduction in dopamine concentration in the striatum and also to a decrease in the expression of tyrosine hydroxylase in striatal neurons. Furthermore, in behavioral tests, exposure to RF-EMF impeded the recovery of locomotor activities after repeated treatments with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). These results suggest that the observed decrease in dopamine concentration in the striatum was caused by both a reduction in the number of dopaminergic neurons and a decline in the number of SVs. The decreased dopamine neuron numbers and concentration seen after RF-EMF exposure would have caused the difficult recovery after MPTP treatment. In summary, our results strongly suggest that exposing the brain to RF-EMF can decrease the number of SVs and dopaminergic neurons in the striatum. These primary changes impair the recovery of locomotor activities following MPTP damage to the striatum.
Collapse
|
2
|
Joshi H, Sharma R, Prashar S, Ho J, Thomson S, Mishra R. Differential Expression of Synapsin I and II upon Treatment by Lithium and Valproic Acid in Various Brain Regions. Int J Neuropsychopharmacol 2018; 21:616-622. [PMID: 29618019 PMCID: PMC6007270 DOI: 10.1093/ijnp/pyy023] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
INTRODUCTION Due to the heterogeneity of psychiatric illnesses and overlapping mechanisms, patients with psychosis are differentially responsive to pharmaceutical drugs. In addition to having therapeutic effects for schizophrenia and bipolar disorder, antipsychotics and mood stabilizers have many clinical applications and are used unconventionally due to their direct and indirect effects on neurotransmitters. Synapsins, a family of neuronal phosphoproteins, play a key regulatory role in neurotransmitter release at synapses. In this study, we investigated the effects of mood stabilizers, lithium, and valproic acid on synapsin gene expression in the rat brain. METHODS Intraperitoneal injections of saline, lithium, and valproic acid were administered to male Sprague Dawley rats twice daily for 14 d, corresponding to their treatment group. Following decapitation and brain tissue isolation, mRNA was extracted from various brain regions including the hippocampus, striatum, prefrontal cortex, and frontal cortex. RESULTS Biochemical analysis revealed that lithium significantly increased gene expression of synapsin I in the striatum, synapsin IIa in the hippocampus and prefrontal cortex, and synapsin IIb in the hippocampus and striatum. Valproic acid significantly increased synapsin IIa in the hippocampus and prefrontal cortex, as well as synapsin IIb in the hippocampus and striatum. CONCLUSION These significant changes in synapsin I and II expression may implicate a common transcription factor, early growth response 1, in its mechanistic pathway. Overall, these results elucidate mechanisms through which lithium and valproic acid act on downstream targets compared with antipsychotics and provide deeper insight on the involvement of synaptic proteins in treating neuropsychiatric illnesses.
Collapse
Affiliation(s)
- Hetshree Joshi
- Department of Psychiatry and Behavioural Neurosciences, McMaster University, Hamilton, Ontario, Canada
| | - Roohie Sharma
- Department of Psychiatry and Behavioural Neurosciences, McMaster University, Hamilton, Ontario, Canada
| | - Shreya Prashar
- Department of Psychiatry and Behavioural Neurosciences, McMaster University, Hamilton, Ontario, Canada
| | - Joella Ho
- Department of Psychiatry and Behavioural Neurosciences, McMaster University, Hamilton, Ontario, Canada
| | - Sharon Thomson
- Department of Psychiatry and Behavioural Neurosciences, McMaster University, Hamilton, Ontario, Canada
| | - Ram Mishra
- Department of Psychiatry and Behavioural Neurosciences, McMaster University, Hamilton, Ontario, Canada,Correspondence: Ram K. Mishra, PhD, Department of Psychiatry and Behavioural Neurosciences, McMaster University, 1280 Main St W. Hamilton, ON L8S 4L8 Canada ()
| |
Collapse
|
3
|
Li YC, Kavalali ET. Synaptic Vesicle-Recycling Machinery Components as Potential Therapeutic Targets. Pharmacol Rev 2017; 69:141-160. [PMID: 28265000 DOI: 10.1124/pr.116.013342] [Citation(s) in RCA: 46] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Presynaptic nerve terminals are highly specialized vesicle-trafficking machines. Neurotransmitter release from these terminals is sustained by constant local recycling of synaptic vesicles independent from the neuronal cell body. This independence places significant constraints on maintenance of synaptic protein complexes and scaffolds. Key events during the synaptic vesicle cycle-such as exocytosis and endocytosis-require formation and disassembly of protein complexes. This extremely dynamic environment poses unique challenges for proteostasis at synaptic terminals. Therefore, it is not surprising that subtle alterations in synaptic vesicle cycle-associated proteins directly or indirectly contribute to pathophysiology seen in several neurologic and psychiatric diseases. In contrast to the increasing number of examples in which presynaptic dysfunction causes neurologic symptoms or cognitive deficits associated with multiple brain disorders, synaptic vesicle-recycling machinery remains an underexplored drug target. In addition, irrespective of the involvement of presynaptic function in the disease process, presynaptic machinery may also prove to be a viable therapeutic target because subtle alterations in the neurotransmitter release may counter disease mechanisms, correct, or compensate for synaptic communication deficits without the need to interfere with postsynaptic receptor signaling. In this article, we will overview critical properties of presynaptic release machinery to help elucidate novel presynaptic avenues for the development of therapeutic strategies against neurologic and neuropsychiatric disorders.
Collapse
Affiliation(s)
- Ying C Li
- Departments of Neuroscience (Y.C.L., E.T.K.) and Physiology (E.T.K.), University of Texas Southwestern Medical Center, Dallas, Texas
| | - Ege T Kavalali
- Departments of Neuroscience (Y.C.L., E.T.K.) and Physiology (E.T.K.), University of Texas Southwestern Medical Center, Dallas, Texas
| |
Collapse
|
4
|
Molinaro L, Hui P, Tan M, Mishra RK. Role of presynaptic phosphoprotein synapsin II in schizophrenia. World J Psychiatry 2015; 5:260-272. [PMID: 26425441 PMCID: PMC4582303 DOI: 10.5498/wjp.v5.i3.260] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/05/2015] [Revised: 04/30/2015] [Accepted: 06/11/2015] [Indexed: 02/05/2023] Open
Abstract
Synapsin II is a member of the neuronal phosphoprotein family. These phosphoproteins are evolutionarily conserved across many organisms and are important in a variety of synaptic functions, including synaptogenesis and the regulation of neurotransmitter release. A number of genome-wide scans, meta-analyses, and genetic susceptibility studies have implicated the synapsin II gene (3p25) in the etiology of schizophrenia (SZ) and other psychiatric disorders. Further studies have found a reduction of synapsin II mRNA and protein in the prefrontal cortex in post-mortem samples from schizophrenic patients. Disruptions in the expression of this gene may cause synaptic dysfunction, which can result in neurotransmitter imbalances, likely contributing to the pathogenesis of SZ. SZ is a costly, debilitating psychiatric illness affecting approximately 1.1% of the world’s population, amounting to 51 million people today. The disorder is characterized by positive (hallucinations, paranoia), negative (social withdrawal, lack of motivation), and cognitive (memory impairments, attention deficits) symptoms. This review provides a comprehensive summary of the structure, function, and involvement of the synapsin family, specifically synapsin II, in the pathophysiology of SZ and possible target for therapeutic intervention/implications.
Collapse
|
5
|
Nesher E, Koman I, Gross M, Tikhonov T, Bairachnaya M, Salmon-Divon M, Levin Y, Gerlitz G, Michaelevski I, Yadid G, Pinhasov A. Synapsin IIb as a functional marker of submissive behavior. Sci Rep 2015; 5:10287. [PMID: 25998951 PMCID: PMC4441117 DOI: 10.1038/srep10287] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2014] [Accepted: 04/09/2015] [Indexed: 12/22/2022] Open
Abstract
Dominance and submissiveness are important functional elements of the social hierarchy. By employing selective breeding based on a social interaction test, we developed mice with strong and stable, inheritable features of dominance and submissiveness. In order to identify candidate genes responsible for dominant and submissive behavior, we applied transcriptomic and proteomic studies supported by molecular, behavioral and pharmacological approaches. We clearly show here that the expression of Synapsin II isoform b (Syn IIb) is constitutively upregulated in the hippocampus and striatum of submissive mice in comparison to their dominant and wild type counterparts. Moreover, the reduction of submissive behavior achieved after mating and delivery was accompanied by a marked reduction of Syn IIb expression. Since submissiveness has been shown to be associated with depressive-like behavior, we applied acute SSRI (Paroxetine) treatment to reduce submissiveness in studied mice. We found that reduction of submissive behavior evoked by Paroxetine was paired with significantly decreased Syn IIb expression. In conclusion, our findings indicate that submissiveness, known to be an important element of depressive-like behavioral abnormalities, is strongly linked with changes in Syn IIb expression.
Collapse
Affiliation(s)
- Elimelech Nesher
- 1] Department of Molecular Biology. Ariel University, Ariel. Israel [2] Faculty of Life Sciences. Bar-Ilan University, Ramat Gan. Israel
| | - Igor Koman
- Department of Molecular Biology. Ariel University, Ariel. Israel
| | - Moshe Gross
- Department of Molecular Biology. Ariel University, Ariel. Israel
| | - Tatiana Tikhonov
- Department of Molecular Biology. Ariel University, Ariel. Israel
| | | | | | - Yishai Levin
- de Botton Institute for Protein Profiling, The Nancy and Stephen Grand Israel National Center for Personalized Medicine. Weizmann Institute of Science, Rehovot. Israel
| | - Gabi Gerlitz
- Department of Molecular Biology. Ariel University, Ariel. Israel
| | - Izhak Michaelevski
- 1] Department of Biochemistry and Molecular Biology. Tel-Aviv University, Tel-Aviv. Israel [2] Sagol School of Neuroscience, Tel-Aviv University, Tel-Aviv. Israel
| | - Gal Yadid
- Faculty of Life Sciences. Bar-Ilan University, Ramat Gan. Israel
| | - Albert Pinhasov
- Department of Molecular Biology. Ariel University, Ariel. Israel
| |
Collapse
|
6
|
Basu D, Tian Y, Hui P, Bhandari J, Johnson RL, Mishra RK. Change in expression of vesicular protein synapsin II by chronic treatment with D2 allosteric modulator PAOPA. Peptides 2015; 66:58-62. [PMID: 25703303 DOI: 10.1016/j.peptides.2015.01.004] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/29/2014] [Revised: 01/20/2015] [Accepted: 01/20/2015] [Indexed: 12/21/2022]
Abstract
The hallmark symptoms of schizophrenia include profound disturbances in thought, perception, cognition etc., which negatively impacts an individual's quality of life. Current antipsychotic drugs are not effective in treating all symptoms of this disorder, and often cause severe movement and metabolic side effects. Consequently, there remains a strong impetus to develop safer and more efficacious therapeutics for patients, as well as elucidating the etiology of schizophrenia. Previous work in our lab has introduced a novel candidate for the treatment of this disease: the dopamine D2 receptor (D2R) allosteric modulator, 3(R)-[(2(S)-pyrrolidinylcarbonyl)amino]-2-oxo-1-pyrrolidineacetamide (PAOPA). We have previously shown that PAOPA, by selectively modulating D2R, can ameliorate schizophrenia-like symptoms in animal models, although the precise mechanism is presently not understood. Synapsin II is a presynaptic vesicular protein which has been strongly implicated in schizophrenia, as it is reduced in the prefrontal cortex of patients, and knockdown of this protein elicits schizophrenia-like phenotypes in animal models. Given the therapeutic effects of PAOPA and the role of synapsin II in schizophrenia, the objective of this study was to investigate the effect of chronic administration of PAOPA (45 days) on neuronal synapsin II protein expression in rodents. Immunoblot results revealed that the synapsin IIa, but not the IIb isoform, was increased in the dopaminergic regions of the striatum, nucleus accumbens, and medial prefrontal cortex. The results of this study implicate a role for modulation of synapsin II as a possible therapeutic mechanism of action for potential antipsychotic drug PAOPA.
Collapse
Affiliation(s)
- Dipannita Basu
- Department of Psychiatry and Behavioural Neurosciences, McMaster University, 1200 Main St. W., Hamilton, ON, Canada L8N 3Z5
| | - Yuxin Tian
- Department of Psychiatry and Behavioural Neurosciences, McMaster University, 1200 Main St. W., Hamilton, ON, Canada L8N 3Z5
| | - Patricia Hui
- Department of Psychiatry and Behavioural Neurosciences, McMaster University, 1200 Main St. W., Hamilton, ON, Canada L8N 3Z5
| | - Jayant Bhandari
- Department of Psychiatry and Behavioural Neurosciences, McMaster University, 1200 Main St. W., Hamilton, ON, Canada L8N 3Z5
| | - Rodney L Johnson
- Department of Medicinal Chemistry, University of Minnesota, 308 Harvard Street SE, Minneapolis, MN 55455, USA
| | - Ram K Mishra
- Department of Psychiatry and Behavioural Neurosciences, McMaster University, 1200 Main St. W., Hamilton, ON, Canada L8N 3Z5.
| |
Collapse
|
7
|
Protein kinase G regulates dopamine release, ΔFosB expression, and locomotor activity after repeated cocaine administration: involvement of dopamine D2 receptors. Neurochem Res 2013; 38:1424-33. [PMID: 23585124 DOI: 10.1007/s11064-013-1040-1] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2013] [Revised: 03/26/2013] [Accepted: 04/06/2013] [Indexed: 01/11/2023]
Abstract
Protein kinase G (PKG) activation has been implicated in the regulation of synaptic plasticity in the brain. This study was conducted to determine the involvement of PKG-associated dopamine D2 (D2) receptors in the regulation of dopamine release, ΔFosB expression and locomotor activity in response to repeated cocaine exposure. Repeated systemic injections of cocaine (20 mg/kg), once a day for seven consecutive days, increased cyclic guanosine monophosphate (cGMP) and extracellular dopamine concentrations in the dorsal striatum. Inhibition of neuronal nitric oxide synthase (nNOS), cGMP or PKG and stimulation of D2 receptors decreased the repeated cocaine-induced increase in dopamine concentrations. Similar results were obtained by the combining nNOS, cGMP or PKG inhibition with stimulation of D2 receptors. Parallel to these data, PKG inhibition, D2 receptor stimulation, and combining PKG inhibition with stimulation of D2 receptors decreased the repeated cocaine-induced increases in ΔFosB expression and locomotor activity. These findings suggest that control of D2 receptors by PKG activation after repeated cocaine is responsible for upregulating dopamine release and sustained long-term changes in gene expression in the dopamine terminals and gamma-aminobutyric acid neurons of the dorsal striatum, respectively. This upregulation may contribute to behavioral changes in response to repeated exposure to cocaine.
Collapse
|
8
|
Synapsin II gene expression in the dorsolateral prefrontal cortex of brain specimens from patients with schizophrenia and bipolar disorder: effect of lifetime intake of antipsychotic drugs. THE PHARMACOGENOMICS JOURNAL 2013; 14:63-9. [PMID: 23529008 PMCID: PMC3970980 DOI: 10.1038/tpj.2013.6] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/28/2012] [Revised: 01/04/2013] [Accepted: 02/04/2013] [Indexed: 01/31/2023]
Abstract
Synapsins are neuronal phosphoproteins crucial to regulating the processes required for normal neurotransmitter release. Synapsin II, in particular, has been implied as a candidate gene for schizophrenia. This study investigated synapsin II mRNA expression, using Real Time RT-PCR, in coded dorsolateral prefrontal cortical samples provided by the Stanley Foundation Neuropathology Consortium. Synapsin IIa was decreased in patients with schizophrenia when compared to both healthy subjects and patients with bipolar disorder, whereas the synapsin IIb was only significantly reduced in patients with schizophrenia when compared to healthy subjects, but not patients with bipolar disorder. Furthermore, lifetime antipsychotic drug use was positively associated with synapsin IIa expression in patients with schizophrenia. Results suggest that impairment of synaptic transmission by synapsin II reduction may contribute to dysregulated convergent molecular mechanisms which result in aberrant neural circuits that characterize schizophrenia, while implicating involvement of synapsin II in therapeutic mechanisms of currently prescribed antipsychotic drugs.
Collapse
|
9
|
Dyck BA, Tan ML, Daya RP, Basu D, Sookram CDR, Thomas N, Mishra RK. Behavioral effects of non-viral mediated RNA interference of synapsin II in the medial prefrontal cortex of the rat. Schizophr Res 2012; 137:32-8. [PMID: 22341900 DOI: 10.1016/j.schres.2012.01.029] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/08/2011] [Revised: 01/20/2012] [Accepted: 01/24/2012] [Indexed: 02/08/2023]
Abstract
Synapsin II is a synaptic vesicle-associated phosphoprotein that has been implicated in the pathophysiology of schizophrenia. Researchers have demonstrated reductions in synapsin II mRNA and protein in post-mortem prefrontal cortex and hippocampus samples from patients with schizophrenia. Synapsin II protein expression has been shown to be regulated by dopamine D(1) and D(2) receptor activation. Furthermore, behavioral testing of the synapsin II knockout mouse has revealed a schizophrenic-like behavioral phenotype in this mutant strain, suggesting a relationship between dysregulated and/or reduced synapsin II and schizophrenia. However, it remains unknown the specific regions of the brain of which perturbations in synapsin II play a role in the pathophysiology of this disease. The aim of this project was to evaluate animals with a selective knock-down of synapsin II in the medial prefrontal cortex through the use of siRNA technology. Two weeks after continuous infusion of synapsin II siRNAs, animals were examined for the presence of a schizophrenic-like behavioral phenotype. Our results reveal that rats with selective reductions in medial prefrontal cortical synapsin II demonstrate deficits in sensorimotor gating (prepulse inhibition), hyperlocomotion, and reduced social behavior. These results implicate a role for decreased medial prefrontal cortical synapsin II levels in the pathophysiology of schizophrenia and the mechanisms of aberrant prefrontal cortical circuitry, and suggest that increasing synapsin II levels in the medial prefrontal cortex may potentially serve as a novel therapeutic target for this devastating disorder.
Collapse
Affiliation(s)
- Bailey A Dyck
- Department of Psychiatry and Behavioural Neurosciences, McMaster University, Hamilton, ON, Canada
| | | | | | | | | | | | | |
Collapse
|
10
|
Dyck BA, Beyaert MGR, Ferro MA, Mishra RK. Medial prefrontal cortical synapsin II knock-down induces behavioral abnormalities in the rat: examining synapsin II in the pathophysiology of schizophrenia. Schizophr Res 2011; 130:250-9. [PMID: 21689907 DOI: 10.1016/j.schres.2011.05.017] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/06/2011] [Revised: 05/17/2011] [Accepted: 05/19/2011] [Indexed: 01/11/2023]
Abstract
Synapsin II is a synaptic vesicle-associated phosphoprotein that has been implicated in the pathophysiology of schizophrenia. Studies have demonstrated reductions in synapsin II mRNA and protein in medial prefrontal cortical post-mortem samples from patients with schizophrenia, genetic associations between synapsin II and schizophrenia, and synapsin II protein regulation by dopamine receptor activation. Collectively, this research indicates a relationship between synapsin II dysregulation and schizophrenia; however, it remains unknown whether perturbations in synapsin II play a role in the pathophysiology of this disease. The aim of this project was to evaluate animals with selective knock-down of synapsin II in the medial prefrontal cortex. After continuous infusion of synapsin II antisense sequences, animals were examined for the presence of schizophrenic-like behavioral phenotypes and assessed on the response to clinically relevant antipsychotic drugs. Our results indicate that rats with selective reductions in medial prefrontal cortical synapsin II demonstrate deficits in sensorimotor gating (prepulse inhibition), reduced social behavior, and hyperlocomotion, which are corrected by the atypical antipsychotic drug olanzapine. Additionally, synapsin II knock-down disrupts serial search efficiency. These behavioral changes are accompanied by reductions in vesicular neurotransmitter transporter protein concentrations for glutamate (VGLUT1 and VGLUT2) and GABA (VGAT), without affecting dopamine (VMAT2). These results implicate a causal role for decreased synapsin II in the medial prefrontal cortex in the pathophysiology of schizophrenia and the mechanisms of aberrant prefrontal cortical circuitry, and suggest that synapsin II may potentially serve as a novel therapeutic target for this disorder.
Collapse
Affiliation(s)
- Bailey A Dyck
- Department of Psychiatry and Behavioral Neurosciences, McMaster University, Hamilton, ON, Canada, L8N 3Z5
| | | | | | | |
Collapse
|
11
|
Guest KA, Dyck BA, Shethwala S, Mishra RK. Atypical antipsychotic drugs upregulate synapsin II in the prefrontal cortex of post-mortem samples obtained from patients with schizophrenia. Schizophr Res 2010; 120:229-31. [PMID: 20434888 DOI: 10.1016/j.schres.2010.03.029] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/11/2010] [Revised: 03/22/2010] [Accepted: 03/25/2010] [Indexed: 12/21/2022]
|
12
|
Hazy TE, Frank MJ, O’Reilly RC. Neural mechanisms of acquired phasic dopamine responses in learning. Neurosci Biobehav Rev 2010; 34:701-20. [PMID: 19944716 PMCID: PMC2839018 DOI: 10.1016/j.neubiorev.2009.11.019] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2009] [Revised: 11/19/2009] [Accepted: 11/19/2009] [Indexed: 10/20/2022]
Abstract
What biological mechanisms underlie the reward-predictive firing properties of midbrain dopaminergic neurons, and how do they relate to the complex constellation of empirical findings understood as Pavlovian and instrumental conditioning? We previously presented PVLV, a biologically inspired Pavlovian learning algorithm accounting for DA activity in terms of two interrelated systems: a primary value (PV) system, which governs how DA cells respond to a US (reward) and; a learned value (LV) system, which governs how DA cells respond to a CS. Here, we provide a more extensive review of the biological mechanisms supporting phasic DA firing and their relation to the spate of Pavlovian conditioning phenomena and their sensitivity to focal brain lesions. We further extend the model by incorporating a new NV (novelty value) component reflecting the ability of novel stimuli to trigger phasic DA firing, providing "novelty bonuses" which encourages exploratory working memory updating and in turn speeds learning in trace conditioning and other working memory-dependent paradigms. The evolving PVLV model builds upon insights developed in many earlier computational models, especially reinforcement learning models based on the ideas of Sutton and Barto, biological models, and the psychological model developed by Savastano and Miller. The PVLV framework synthesizes these various approaches, overcoming important shortcomings of each by providing a coherent and specific mapping to much of the relevant empirical data at both the micro- and macro-levels, and examines their relevance for higher order cognitive functions.
Collapse
Affiliation(s)
- Thomas E. Hazy
- Department of Psychology and Neuroscience University of Colorado Boulder, 345 UCB, Boulder, CO 80309
| | - Michael J. Frank
- Departments of Psychology and Cognitive and Linguistic Sciences Brown University, 190 Thayer Street, Providence, RI 02912
| | - Randall C. O’Reilly
- Department of Psychology and Neuroscience University of Colorado Boulder, 345 UCB, Boulder, CO 80309
| |
Collapse
|
13
|
Role of AP-2alpha transcription factor in the regulation of synapsin II gene expression by dopamine D1 and D2 receptors. J Mol Neurosci 2009; 41:267-77. [PMID: 19842069 DOI: 10.1007/s12031-009-9299-z] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2009] [Accepted: 10/02/2009] [Indexed: 01/11/2023]
Abstract
Synapsins are a family of neuron-specific phosphoproteins involved in synaptic vesicle docking, synaptogenesis, and synaptic plasticity. Previous studies have reported an increase in synapsin II protein by dopaminergic agents in the striatum, medial prefrontal cortex, and nucleus accumbens. This study investigated the mechanistic pathway involved in synapsin II regulation by dopaminergic drugs using primary midbrain neurons to determine which of several transcription factors regulates synapsin II expression. Protein kinase A (PKA) participation in the signaling pathway was examined using selective PKA inhibitors, which reduced synapsin II expression in cell cultures while dopaminergic agents were unable to increase synapsin II in the presence of the PKA inhibitor. Transcription factor involvement was further investigated using separate cultures treated with antisense deoxyoligonucleotides (ADONs) against the following transcription factors: activating protein 2 alpha (AP-2alpha), early growth response factor 1 (EGR-1), or polyoma enhancer activator-3 (PEA-3). Selective knockdown of AP-2alpha by ADONs reduced synapsin II levels, whereas treatment with EGR-1 and PEA-3 ADONs did not affect synapsin II expression. Furthermore, dopaminergic agents were no longer able to influence synapsin II concentrations following AP-2alpha knockdown. Collectively, these results indicate that a cyclic adenosine-3',5'-monophosphate/PKA-dependent mechanism involving the AP-2alpha transcription factor is likely responsible for the increase in neuronal synapsin II following dopamine D1 receptor stimulation or dopamine D2 receptor inhibition.
Collapse
|
14
|
Dyck BA, Skoblenick KJ, Castellano JM, Ki K, Thomas N, Mishra RK. Behavioral abnormalities in synapsin II knockout mice implicate a causal factor in schizophrenia. Synapse 2009; 63:662-72. [PMID: 19360855 DOI: 10.1002/syn.20643] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Recent studies on the phosphoprotein synapsin II have revealed reduced expression in postmortem medial prefrontal cortex tissues from subjects with schizophrenia, and chronic antipsychotic drug treatment has resulted in concurrent increases in synapsin II mRNA and protein levels. Collectively, this research suggests a role of synapsin II in the pathophysiology of schizophrenia; however, whether synapsin II plays a causal role in this disease process still remains unclear. Therefore, the goal of this investigation was to examine whether synapsin II knockout mice display behavioral abnormalities commonly expressed in preclinical animal models of schizophrenia, namely deficits in prepulse inhibition (PPI), decreased social behavior, and locomotor hyperactivity. Results indicate that mice with knockout of the synapsin II gene demonstrate deficits in PPI at three prepulse intensities (67, 70, and 73 dB), along with deficits in habituation to startle to a 110 dB acoustic pulse. Knockout animals also expressed decreased social behavior and increased locomotor activity when compared to wildtype and heterozygous populations. Complete knockout of the synapsin II gene was confirmed in postmortem brain tissues via immunoblotting. In conclusion, these results confirm that synapsin II knockout mice display behavioral endophenotypes similar to established preclinical animal models of schizophrenia, and lend support to the notion that abnormalities in synapsin II expression may play a causal role in the underlying pathophysiological mechanisms of schizophrenia.
Collapse
Affiliation(s)
- Bailee A Dyck
- Department of Psychiatry and Behavioral Neurosciences, McMaster University, Hamilton, Ontario, Canada
| | | | | | | | | | | |
Collapse
|
15
|
Fasano C, Poirier A, DesGroseillers L, Trudeau LE. Chronic activation of the D2 dopamine autoreceptor inhibits synaptogenesis in mesencephalic dopaminergic neuronsin vitro. Eur J Neurosci 2008; 28:1480-90. [DOI: 10.1111/j.1460-9568.2008.06450.x] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
|
16
|
Dyck BA, Skoblenick KJ, Castellano JM, Ki K, Thomas N, Mishra RK. Synapsin II knockout mice show sensorimotor gating and behavioural abnormalities similar to those in the phencyclidine-induced preclinical animal model of schizophrenia. Schizophr Res 2007; 97:292-3. [PMID: 17900867 DOI: 10.1016/j.schres.2007.08.026] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/25/2007] [Revised: 08/22/2007] [Accepted: 08/24/2007] [Indexed: 02/08/2023]
|
17
|
Saviouk V, Moreau MP, Tereshchenko IV, Brzustowicz LM. Association of synapsin 2 with schizophrenia in families of Northern European ancestry. Schizophr Res 2007; 96:100-11. [PMID: 17766091 PMCID: PMC2169360 DOI: 10.1016/j.schres.2007.07.031] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/26/2007] [Revised: 07/27/2007] [Accepted: 07/31/2007] [Indexed: 12/21/2022]
Abstract
The synapsin 2 (Syn2) gene (3p25) is implicated in synaptogenesis, neurotransmitter release, and the localization of nitric oxide synthase to the proximity of its targets. In this study we investigated linkage and association between the Syn2 locus and schizophrenia. 37 pedigrees of Northern European ancestry from the NIMH Human Genetics Initiative collection were used. Four microsatellites and twenty SNPs were genotyped. Linkage (FASTLINK) and association (TRANSMIT, PDTPHASE) between markers and schizophrenia were evaluated. A maximum heterogeneity LOD of 1.93 was observed at marker D3S3434 with a recessive mode of inheritance. Significant results were obtained for association with schizophrenia using TRANSMIT (minimum nominal p=0.0000005) and PDTPHASE (minimum nominal p=0.014) using single marker analyses. Haplotype analysis using markers in introns 5 and 6 of Syn2 provided a single haplotype that is significantly associated with schizophrenia using TRANSMIT (nominal p<0.00000001) and PDTPHASE (nominal p=0.02). Simulation studies confirm the global significance of these results, but demonstrate that the small p-values generated by the bootstrap routine of TRANSMIT can be consistently anticonservative. Review of the literature suggests that Syn2 is likely to be involved in the etiology or pathogenesis of schizophrenia.
Collapse
|
18
|
Thomas EA. Molecular profiling of antipsychotic drug function: convergent mechanisms in the pathology and treatment of psychiatric disorders. Mol Neurobiol 2007; 34:109-28. [PMID: 17220533 DOI: 10.1385/mn:34:2:109] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2006] [Revised: 11/30/1999] [Accepted: 06/21/2006] [Indexed: 02/05/2023]
Abstract
Despite great progress in antipsychotic drug research, the molecular mechanisms by which these drugs work have remained elusive. High-throughput gene profiling methods have advanced this field by allowing the simultaneous investigation of hundreds to thousands of genes. However, different methodologies, choice of brain region, and drugs studied have made comparisons across different studies difficult. Because of the complexity of gene expression changes caused by drugs, teasing out the most relevant expression differences is a challenging task. One approach is to focus on gene expression changes that converge on the same systems that were previously deemed important to the pathology of psychiatric disorders. From the microarray studies performed on human postmortem brain samples from schizophrenics, the systems most implicated to be dysfunctional are synaptic machinery, oligodendrocyte/myelin function, and mitochondrial/ubiquitin metabolism. Drugs may act directly or indirectly to compensate for underlying pathological deficits in schizophrenia or via other mechanisms that converge on these pathways. Side effects, consisting of motor and metabolic dysfunction (which occur with typical and atypical drugs, respectively), also may be mediated by gene expression changes that have been reported in these studies. This article surveys both the convergent antipsychotic mechanisms and the genes that may be responsible for other effects elicited by antipsychotic drugs.
Collapse
Affiliation(s)
- Elizabeth A Thomas
- Department of Molecular Biology, The Scripps Research Institute, La Jolla, CA, USA.
| |
Collapse
|