SEROTONIN FACILITATES SYNAPTIC PLASTICITY IN KITTEN VISUAL-CORTEX - AN IN-VITRO STUDY

We have addressed the role of serotonin-2C (5-HT2C) receptors in the d evelopment and maintenance of synaptic plasticity in the kitten visual cortex. In visual cortical slices, taken from 40- to 80-day-old kitte ns, bath application of serotonin markedly facilitated the induction o f both long-term depression (LTD) and long-term potentiation (LTP). Fi eld potential responses to white matter stimulation were recorded from layer IV after a regime of low frequency stimulation (LFS; 1 Hz, 15 m in), which reliably induced LTP or LTD in younger kittens (less than 3 0 days of age). At 40-80 days, this protocol almost never induced LTD or LTP in layer IV. However, in 50% of the visual cortical slices stud ied in 40-80-day-old kittens, LTD or LTP was induced, if serotonin (1 or 10 mu M) was co-applied with LFS. No such serotonin facilitation of long-term plasticity was ever detected in > 120-day-old animals, indi cating that serotonin facilitates synaptic plasticity within a defined period of visual cortical development. Serotonergic 5-HT2C receptors are likely to contribute to the synaptic plasticity observed in layer IV, since mesulergine, an antagonist of the 5-HT2C receptor, completel y blocked synaptic modifications induced by the combination of low fre quency stimulation and serotonin application. (C) 1997 Elsevier Scienc e B.V.