Chronic estrogen effects on 5-hydroxytryptamine-mediated responses in hippocampal pyramidal cells of female rats.

Intracellular recording techniques were used to assess the effect of chronic estrogen treatment of ovariectomized (OVX) rats on CA1 pyramidal cell properties and serotonin (5-HT)-mediated responses in the dorsal hippocampus. The magnitude of the 5-HT1A-mediated hyperpolarization and concomitant change in membrane resistance elicited by 15 microM 5-HT was greater in pyramidal cells from OVX rats treated with estrogen (OVX + ES) than in pyramidal cells from OVX rats. Estrogen treatment did not alter the cellular membrane properties or the reduction in AHP amplitude elicited by 15 microM 5-HT. The modulation of 5-HT neurotransmission by estrogen may contribute to variations in mood which are associated with the menstrual cycle.