Endogenous 5-HT inhibits firing activity of hippocampal CA1 pyramidal neurons during conditioned fear stress-induced freezing behavior through stimulating 5-HT1A receptors.
This study examines the activity of hippocampal CA, pyramidal neurons during conditioned fear stress (CFS)-induced freezing behavior in unanesthetized, unrestrained rats. The firing frequency of hippocampal CA1 pyramidal neurons was significantly decreased when conditioned rats exhibited freezing behavior. Firing frequency returned to the baseline after freezing behavior disappeared. The selective 5-hydroxytryptamine (5-HT)1A antagonists, N-[2-[4-(2-methoxyphenyl)-1-piperazinyl]ethyl]-N-(2-pyridinyl)cyclohexanecarboxamide (WAY-100635), and N-tert-butyl-3-[4-(2-methoxyphenyl)piperazine-1-yl]-2-phenylpropamide (WAY-100135) and 5-HT depletion with parachlorophenylalanine (PCPA) completely abolished the decrease in firing frequency during CFS-induced freezing behavior. These results suggested that endogenous 5-HT inhibited the firing activity of hippocampal CA1 pyramidal neurons during CFS-induced freezing behavior mainly through stimulating 5-HT1A receptors.
Tada
Koji
K
Department of Neuropsychiatry, Nihon University, School of Medicine, Oyaguchi Kamimachi 30-1, Itabashi, Tokyo 173-8610, Japan. koji@med.nihon-u.ac.jp
Kasamo
Kimihiro
K
Suzuki
Tadashi
T
Matsuzaki
Yamato
Y
Kojima
Takuya
T
D000818:Animals; D003213:Conditioning, Psychological / Q000187:drug effects / Q000502:physiology*; D004594:Electrophysiology; D005239:Fear / Q000502:physiology*; D010134:Fenclonine / Q000494:pharmacology; D006624:Hippocampus / Q000166:cytology* / Q000187:drug effects / Q000502:physiology*; D008297:Male; D017551:Microdialysis; D010879:Piperazines / Q000494:pharmacology; D017966:Pyramidal Cells / Q000187:drug effects / Q000502:physiology*; D011725:Pyridines / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D044282:Receptor, Serotonin, 5-HT1A / Q000187:drug effects / Q000502:physiology*; D012701:Serotonin / Q000502:physiology*; D018490:Serotonin Agents / Q000494:pharmacology; D012702:Serotonin Antagonists / Q000494:pharmacology; D013315:Stress, Psychological / Q000503:physiopathology*
D010879:Piperazines; D011725:Pyridines; D018490:Serotonin Agents; D012702:Serotonin Antagonists; D044282:Receptor, Serotonin, 5-HT1A; C081293:WAY 100135; D012701:Serotonin; C090413:N-(2-(4-(2-methoxyphenyl)-1-piperazinyl)ethyl)-N-(2-pyridinyl)cyclohexanecarboxamide; D010134:Fenclonine