EFFECTS OF SEROTONIN ON SYNAPTIC AND INTRINSIC-PROPERTIES OF RAT SUBICULAR NEURONS IN-VITRO

Intracellular recordings were performed to study the effects of 5-HT o n membrane properties and EPSP/LPSP responses of subicular neurons in rat combined hippocampal-entorhinal cortex slices. Application of 5-HT induced in 76% of the investigated subicular cells a hyperpolarizatio n and a reduction of membrane resistance. In bursting neurons, 5-HT ca used a reduction of the depolarizing envelope underlying burst dischar ges and attenuated the subsequent afterhyperpolarization. While 5-HT d ecreased isolated AMPA/kainate and NMDA receptor-mediated responses as well as slow IPSPs, we could not find a consistent effect on isolated fast IPSPs. Since in approximate to 25% of subicular neurons EPSPs an d slow IPSPs were reduced without any increase of membrane conductance , we conclude that 5-HT has in addition to membrane effects also effec ts on synaptic currents. (C) 1997 Elsevier Science B.V.