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Salavati B, Rajji TK, Price R, Sun Y, Graff-Guerrero A, Daskalakis ZJ. Imaging-based neurochemistry in schizophrenia: a systematic review and implications for dysfunctional long-term potentiation. Schizophr Bull 2015; 41:44-56. [PMID: 25249654 PMCID: PMC4266301 DOI: 10.1093/schbul/sbu132] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Cognitive deficits are commonly observed in patients with schizophrenia. Converging lines of evidence suggest that these deficits are associated with impaired long-term potentiation (LTP). In our systematic review, this hypothesis is evaluated using neuroimaging literature focused on proton magnetic resonance spectroscopy, positron emission tomography, and single-photon emission computed tomography. The review provides evidence for abnormal dopaminergic, GABAergic, and glutamatergic neurotransmission in antipsychotic-naive/free patients with schizophrenia compared with healthy controls. The review concludes with a model illustrating how these abnormalities could lead to impaired LTP in patients with schizophrenia and consequently cognitive deficits.
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Affiliation(s)
- Bahar Salavati
- Institute of Medical Science, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada;,Temerty Centre for Therapeutic Brain Intervention, Centre for Addiction and Mental Health, Toronto, Ontario, Canada
| | - Tarek K. Rajji
- *To whom correspondence should be addressed; 80 Workman Way, Room 6312, Toronto, Ontario M6J 1H4, Canada; tel: +1 416 535 8501 x 33661; fax: +1 416 583 1307; e-mail:
| | - Rae Price
- Institute of Medical Science, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada;,Temerty Centre for Therapeutic Brain Intervention, Centre for Addiction and Mental Health, Toronto, Ontario, Canada
| | - Yinming Sun
- Temerty Centre for Therapeutic Brain Intervention, Centre for Addiction and Mental Health, Toronto, Ontario, Canada
| | - Ariel Graff-Guerrero
- Institute of Medical Science, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada
| | - Zafiris J. Daskalakis
- Institute of Medical Science, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada;,Temerty Centre for Therapeutic Brain Intervention, Centre for Addiction and Mental Health, Toronto, Ontario, Canada;,Department of Psychiatry, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada;,Campbell Family Mental Health Research Institute, Centre for Addiction and Mental Health, Toronto, Ontario, Canada
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Carter LP, Koek W, France CP. Lack of effects of GHB precursors GBL and 1,4-BD following i.c.v. administration in rats. Eur J Neurosci 2007; 24:2595-600. [PMID: 17100847 DOI: 10.1111/j.1460-9568.2006.05146.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Gamma-hydroxybutyrate (GHB) is used therapeutically and recreationally worldwide. Since the scheduling of GHB by the USA and the United Nations in 2000-2001, the recreational use of GHB precursors has reportedly increased. The aim of this study was to examine if potency differences of GHB and GHB-like compounds are due to their blood-brain barrier permeability. The effects of peripheral and central administration of GHB, GHB precursors gamma-butyrolactone (GBL) and 1,4-butanediol (1,4-BD), and the gamma-aminobutyric acid (GABA)(B) receptor agonist baclofen on schedule-controlled responding were examined in rats. GHB and baclofen were 276- and 253-fold more potent, respectively, after intracerebroventricular (i.c.v.) administration than after intraperitoneal (i.p.) administration, whereas GBL and 1,4-BD, up to a dose of 1780 microg were without effect after i.c.v. administration. These data suggest that GBL and 1,4-BD are not metabolically converted to GHB in the brain, that enhanced brain penetration cannot account for potency differences between compounds, and that baclofen, like GHB, can readily cross the blood-brain barrier.
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Affiliation(s)
- Lawrence P Carter
- The University of Texas Health Science Center at San Antonio, 7703 Floyd Curl Drive - MC7764, San Antonio, TX 78229, USA
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Collares EF, Vinagre AM. Effect of the GABAB agonist baclofen on dipyrone-induced delayed gastric emptying in rats. Braz J Med Biol Res 2005; 38:99-104. [PMID: 15665995 DOI: 10.1590/s0100-879x2005000100015] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Dipyrone administered intravenously (iv) or intracerebroventricularly (icv) delays gastric emptying (GE) in rats. Gamma-aminobutyric acid (GABA) is the most potent inhibitory neurotransmitter of the central nervous system. The objective of the present study was to determine the effect of icv baclofen, a GABAB receptor agonist, on delayed GE induced by dipyrone. Adult male Wistar rats received a saline test meal containing phenol red as a marker. GE was indirectly evaluated by determining the percent of gastric retention (%GR) of the meal 10 min after orogastric administration. In the first experiment, the animals were injected iv with vehicle (Civ) or 80 mg/kg (240 micromol/kg) dipyrone (Dpiv), followed by icv injection of 10 microl vehicle (bac0), or 0.5 (bac0.5), 1 (bac1) or 2 microg (bac2) baclofen. In the second experiment, the animals were injected icv with 5 microl vehicle (Cicv) or an equal volume of a solution containing 4 micromol (1333.2 microg) dipyrone (Dpicv), followed by 5 microl vehicle (bac0) or 1 microg baclofen (bac1). GE was determined 10 min after icv injection. There was no significant difference between control animals from one experiment to another concerning GR values. Baclofen at the doses of 1 and 2 microg significantly reduced mean %GR induced by iv dipyrone (Dpivbac1 = 35.9% and Dpivbac2 = 26.9% vs Dpivbac0 = 51.8%). Similarly, baclofen significantly reduced the effect of dipyrone injected icv (mean %GR: Dpicvbac1 = 30.4% vs Dpicvbac0 = 54.2%). The present results suggest that dipyrone induces delayed GE through a route in the central nervous system that is blocked by the activation of GABAB receptors.
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Affiliation(s)
- E F Collares
- Departamento de Pediatria, Núcleo de Medicina e Cirurgia Experimental and Centro de Investigação em Pediatria, Faculdade de Ciências Médicas, Universidade Estadual de Campinas, Campinas, SP, Brazil.
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Flesher JE, Scheffel U, London ED, Frost JJ. In vivo labeling of nicotinic cholinergic receptors in brain with [3H]cytisine. Life Sci 1994; 54:1883-90. [PMID: 8196506 DOI: 10.1016/0024-3205(94)90146-5] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
[3H]Cytisine was evaluated as an in vivo ligand for the nicotinic cholinergic receptor (nAchR) in mouse brain. The tracer was injected intravenously, and radioactivity in brain regions was analyzed. Radioactivity peaked in the brain at 30 minutes. It was highest in the thalamus, intermediate in the superior colliculi, prefrontal cortex and hippocampus, and low in the cerebellum. Pretreatment with unlabeled cytisine inhibited binding in the thalamus, but not in the cerebellum. Binding was displaced by l-nicotine, but not by d-nicotine or dexetimide. The results suggest that cytisine, appropriately labeled with a positron emitting radionuclide, may be useful for study of nicotinic cholinergic receptors in humans by emission computed tomography.
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Affiliation(s)
- J E Flesher
- Johns Hopkins Medical Institutions, Baltimore, MD 21287
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Yarkov AV, Vorob'ev VV, Gal'chenko AA, Kovalev GI. Electrical activity of the hippocampus of rats with the central administration of GABA agonists and antagonists. NEUROSCIENCE AND BEHAVIORAL PHYSIOLOGY 1991; 21:81-8. [PMID: 1648182 DOI: 10.1007/bf01184246] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The frequency spectra of the electrograms of the dorsal hippocampus with intraventricular administration of GABA, muscimol, baclofen, bicuculline, and picrotoxin, were studied in chronic experiments on 24 awake freely-moving rats. The data obtained are in accord with the existing notion regarding the interactions of agonists and antagonists with GABA receptors. The possibility of their participation in the formation and/or modulation of the total electrical activity of the hippocampus is discussed.
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Affiliation(s)
- A V Yarkov
- Institute of Biological Physics, Academy of Sciences of the USSR [AN SSSR], Pushchino
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Catelli JM, Sved AF. Enhanced pressor response to GABA in the nucleus tractus solitarii of the spontaneously hypertensive rat. Eur J Pharmacol 1988; 151:243-8. [PMID: 3169123 DOI: 10.1016/0014-2999(88)90804-7] [Citation(s) in RCA: 55] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
A previous study from this laboratory demonstrated that ongoing GABAergic neurotransmission in the nucleus tractus solitarii (NTS) functions to maintain baseline arterial pressure (AP). In that study, bilateral microinjection of nipecotic acid into the NTS was observed to elevate AP. Since nipecotic acid is a selective GABA uptake blocker, changes in GABA release should be reflected by changes in the response to nipecotic acid. The present study utilized this approach to assess endogenous GABA activity within the NTS of the spontaneously hypertensive rat (SHR). Male SHR, 16-20 weeks of age, were anesthetized with chloralose, paralyzed and ventilated. Age-matched Wistar-Kyoto (WKY) rats were studied as controls. Bilateral microinjection of nipecotic acid (10 nmol in 100 nl; a maximally effective dose) into the NTS elicited a pressor response which was significantly greater in the SHR than the response observed in the WKY rats. Similarly, direct stimulation of GABAB receptors in the NTS with (-)-baclofen 40 pmol, a maximally effective dose) elicited an increase in AP which was significantly greater in the SHR. In contrast, bilateral microinjection of the direct acting GABAA agonist muscimol (160 pmol, a maximally effective dose) resulted in a similar elevation of AP in both the SHR and WKY rats. These results suggest that the enhanced pressor response caused by endogenous GABA in the NTS of the SHR is due to a greater response evoked by stimulation of GABAB receptors. Thus, enhanced GABAB receptor-mediated neural transmission in the NTS may contribute to the expression or maintenance of hypertension in this genetic model of hypertension.
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Affiliation(s)
- J M Catelli
- Department of Behavioral Neuroscience, University of Pittsburgh, PA 15260
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