Regulation of mating behaviour in the female rat by gonadotropin-releasing hormone in the ventral tegmental area: effects of selective destruction of the A10 dopamine neurones.

Microinfusions of gonadotropin-releasing hormone (GnRH) into the ventral tegmental area (VTA) potentiated lordosis behaviour in oestrogen-primed ovariectomised female rats. Facilitation was observed within 5 min after the infusion and lasted for about 90 min. When GnRH was infused into the VTA of oestrogen-primed animals which were previously subjected to 6-hydroxydopamine treatment (to destroy the A10 dopamine cells), it produced a marked facilitation of lordosis lasting for about 24 h. These results suggest that the A10 dopamine neurones in the VTA may be critically involved in the mechanisms by which GnRH may modulate midbrain circuits involved in the regulation of lordosis behaviour in the female rat. The lesion studies also imply that the A10 dopamine neurones function as inhibitory neurones regulating lordosis behaviour by suppressing the activity of those cells in the VTA which are sensitive to GnRH. Removal of this inhibitory input leads to an exaggerated response.