Estrogen-induced suppression of female rat forebrain neurons with axons to ventral midbrain.

In estrogen-treated and non-treated ovariectomized female rats under urethan anesthesia, 278 neurons were antidromically identified in the medial preoptic and other basal forebrain areas by electrical stimulation of their terminals in the ventral tegmental area. Responses from the estrogen-treated rats had a significantly higher threshold, longer latency and absolute refractory period than those from the non-treated rats. Estrogen may decrease excitability of the preoptic axons along its length.