Abstract
The effect of serotonin 5-HT2 receptor stimulation on long-term potentiation (LTP) in the primary visual cortex was investigated by using rat brain slices in vitro. Field potentials evoked by stimulation of layer IV were recorded in layer II/III. The 5-HT2 receptor agonist 1-(2,5-dimethyl-4-iodophenyl)-2-aminopropane (DOI) did not affect baseline synaptic potentials evoked by single-pulse test stimulation, but significantly inhibited the induction of LTP in a concentration-dependent manner (0.1-10 microM). The LTP-inhibiting effect of DOI (10 microM) was blocked by the 5-HT2,7 receptor antagonist ritanserin (10 microM), but not by the 5-HT1A receptor antagonist NAN-190 (10 microM) nor by the 5-HT3,4 receptor antagonist MDL72222 (10 microM). The inhibitory effect of DOI was also blocked by the phospholipase C inhibitor U73122, but not by its inactive analogue U73343. These results suggest that visual cortex LTP is inhibited by activation of the 5-HT2 receptor-phospholipase C system. In addition, the LTP-inhibiting effect of DOI was abolished by the presence of the GABAA receptor antagonist bicuculline (10 microM), suggesting that 5-HT2 receptor-mediated inhibition of visual cortex LTP is dependent on GABAergic inhibition.
MeSH terms
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8-Hydroxy-2-(di-n-propylamino)tetralin / pharmacology
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Amphetamines / pharmacology
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Animals
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Bicuculline / pharmacology
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Electrophysiology
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Estrenes / pharmacology
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GABA Antagonists / pharmacology
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In Vitro Techniques
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Long-Term Potentiation / drug effects
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Long-Term Potentiation / physiology*
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Male
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Phosphodiesterase Inhibitors / pharmacology
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Piperazines / pharmacology
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Pyrrolidinones / pharmacology
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Rats
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Rats, Wistar
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Receptors, GABA-A / metabolism
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Receptors, Serotonin / metabolism*
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Ritanserin / pharmacology
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Serotonin Antagonists / pharmacology
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Serotonin Receptor Agonists / pharmacology
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Tropanes / pharmacology
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Type C Phospholipases / metabolism*
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Visual Cortex / chemistry*
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Visual Cortex / enzymology*
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gamma-Aminobutyric Acid / physiology
Substances
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Amphetamines
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Estrenes
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GABA Antagonists
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Phosphodiesterase Inhibitors
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Piperazines
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Pyrrolidinones
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Receptors, GABA-A
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Receptors, Serotonin
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Serotonin Antagonists
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Serotonin Receptor Agonists
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Tropanes
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1-(6-((3-methoxyestra-1,3,5(10)-trien-17-yl)amino)hexyl)-1H-pyrrole-2,5-dione
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1-(2-methoxyphenyl)-4-(4-(2-phthalimido)butyl)piperazine
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U 73343
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Ritanserin
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gamma-Aminobutyric Acid
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8-Hydroxy-2-(di-n-propylamino)tetralin
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Type C Phospholipases
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bemesetron
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4-iodo-2,5-dimethoxyphenylisopropylamine
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Bicuculline