title: Effects of Serotonin on the Induction of Long-term Depression in the Rat Visual Cortex.
abstract: Long-term potentiation (LTP) and long-term depression (LTD) have both been studied as mechanisms of ocular dominance plasticity in the rat visual cortex. In a previous study, we suggested that a developmental increase in serotonin [5-hydroxytryptamine (5-HT)] might be involved in the decline of LTP, since 5-HT inhibited its induction. In the present study, to further understand the role of 5-HT in a developmental decrease in plasticity, we investigated the effect of 5-HT on the induction of LTD in the pathway from layer 4 to layer 2/3. LTD was inhibited by 5-HT (10 µM) in 5-week-old rats. The inhibitory effect was mediated by activation of 5-HT(2) receptors. Since 5-HT also regulates the development of visual cortical circuits, we also investigated the role of 5-HT on the development of inhibition. The development of inhibition was retarded by chronic (2 weeks) depletion of endogenous 5-HT in 5-week-old rats, in which LTD was reinstated. These results suggest that 5-HT regulates the induction of LTD directly via activation of 5-HT(2) receptors and indirectly by regulating cortical development. Thus, the present study provides significant insight into the roles of 5-HT on the development of visual cortical circuits and on the age-dependent decline of long-term synaptic plasticity.
authors.affiliation: Department of Physiology, College of Medicine, The Catholic University of Korea, Seoul 137-701, Korea.
authors.forename: Hyun-Jong
authors.initials: HJ
authors.lastname: Jang
authors.forename: Kwang-Hyun
authors.initials: KH
authors.lastname: Cho
authors.forename: Sung-Won
authors.initials: SW
authors.lastname: Park
authors.forename: Myung-Jun
authors.initials: MJ
authors.lastname: Kim
authors.forename: Shin Hee
authors.initials: SH
authors.lastname: Yoon
authors.forename: Duck-Joo
authors.initials: DJ
authors.lastname: Rhie