5-Carboxyamidotryptamine mimics only the 5-HT elicited hyperpolarization of hippocampal pyramidal cells via 5-HT1A receptor.

Perfusion of the rat hippocampal slice in vitro by 5-hydroxytryptamine (5-HT) elicits 3 distinct actions recorded intracellularly from pyramidal cells in area CA1: a hyperpolarization, reduction in spike train elicited afterhyperpolarization (AHP) and depolarization. 5-Carboxyaminotryptamine (5-CT) mimics the membrane hyperpolarization elicited by 5-HT through its action on the 5-HT1A receptor; however, 5-CT does not mimic 5-HT in reducing the amplitude of the AHP or the depolarization of membrane potential. The hyperpolarizing effect of 5-CT is blocked by spiperone. These data provide evidence that the inhibitory effect of 5-HT is mediated primarily by the 5-HT1A receptor.