Serotonin inhibits the induction of NMDA receptor-dependent long-term potentiation in the rat primary visual cortex.
An increase in serotonin [5-hydroxytryptamine (5-HT)] levels in the rat visual cortex is correlated with the developmental decrease in long-term potentiation (LTP), and 5-HT may play an important role in the closure of the critical period by regulating LTP. The effect of 5-HT on the induction of N-methyl-D-aspartate receptor (NMDAR)-dependent and metabotropic glutamate receptor (mGluR)-dependent LTP in visual cortex slices from young rats was investigated. The field potential in layer II/III was recorded by stimulating the underlying layer IV. NMDAR-dependent LTP was induced in slices from 3-week-old rats by theta-burst stimulation (TBS) but not in slices from 5-week-old rats. However, LTP was induced in 5-HT-depleted slices from 5-week-old rats by incubation with para-chloroamphetamine (10 microM, 2 h), a 5-HT-depleting agent. The reinstated LTP in 5-HT-depleted slices was inhibited by the application of D-aminopentanoate, an NMDAR antagonist (50 microM) and 5-HT (10 and 30 microM). In contrast, the induction of mGluR-dependent LTP by weak TBS in disinhibited slices with picrotoxin (1 microM) in the bath was not affected by 5-HT application. The coapplication of 5-HT1A and 5-HT2 receptor agonists inhibited the induction of NMDAR-dependent LTP in 5-HT-depleted slices. 5-HT levels in the visual cortex increased with age. Based on these findings, we conclude that NMDAR-dependent LTP is specifically inhibited by coactivation of 5-HT1A and 5-HT2 receptors with the increase in 5-HT levels in the rat visual cortex at the end of the critical period.
Kim
Hyun-Sok
HS
Department of Physiology, College of Medicine, The Catholic University of Korea, Seoul 137-701, South Korea.
Jang
Hyun-Jong
HJ
Cho
Kwang-Hyun
KH
Hahn
Sang June
SJ
Kim
Myung-Jun
MJ
Yoon
Shin Hee
SH
Jo
Yang-Hyeok
YH
Kim
Myung-Suk
MS
Rhie
Duck-Joo
DJ
D000818:Animals; D004558:Electric Stimulation; D004569:Electroencephalography; D004594:Electrophysiology; D019706:Excitatory Postsynaptic Potentials / Q000187:drug effects; D066298:In Vitro Techniques; D017774:Long-Term Potentiation / Q000187:drug effects*; D051381:Rats; D017207:Rats, Sprague-Dawley; D018094:Receptors, Metabotropic Glutamate / Q000187:drug effects; D016194:Receptors, N-Methyl-D-Aspartate / Q000187:drug effects / Q000502:physiology*; D012701:Serotonin / Q000378:metabolism / Q000494:pharmacology*; D017366:Serotonin Receptor Agonists / Q000494:pharmacology; D013826:Theta Rhythm; D014793:Visual Cortex / Q000187:drug effects*
D018094:Receptors, Metabotropic Glutamate; D016194:Receptors, N-Methyl-D-Aspartate; D017366:Serotonin Receptor Agonists; D012701:Serotonin