Pathways conducting amygdaloid influence on feminine sexual behavior in the rat.

In ovariectomized female rats primed with estradiol benzoate and progesterone, electrochemical stimulation of medial amygdaloid nucleus, anterior part ( AMEa ), increased lordotic frequency, but this effect was not found in rats with transection of the stria terminalis (ST) or the ventral amygdalofugal pathways ( VAF ). On the other hand, the decrease in lordotic frequency observed after stimulation of the posterior part of the lateral amygdaloid nucleus (ALp), persisted in animals with transection of the VAF , but was eliminated in animals with section of the ST. The effect of transecting these pathways on the multiunit and field responses evoked in the hypothalamic ventromedial nucleus (VMN) by stimulation of both amygdaloid nuclei was also studied. Responses evoked by AMEa stimulation were smaller or disappeared after lesion of either the ST or the VAF , but responses evoked by ALp stimulation were affected by lesion of the ST only. Findings are interpreted as suggesting that the ST conducts activity originating in AMEa and ALp which affects sexual receptivity in a complementary fashion, whereas VAF contains AMEa originated fibers whose activation increase receptivity. These behavioral effects may be the consequence of modulatory action on VMN neuronal activity.