Sexual differences in vasopressin receptor binding within the ventrolateral hypothalamus in golden hamsters

In the following studies, the presence of a sexual difference in arginine-vasopressin (AVP) receptor binding was tested within the ventrolateral hypothalamus (VLH), an area rich in gonadal steroid receptors. The density of AVP receptor binding was estimated by in vitro quantitative autoradiography within the entire rostro-caudal extent of the VLH. The density of AVP binding was higher in males than in females at all levels of this area. Furthermore, dependency on testosterone treatment was also compared between gonadectomized males and females. While gonadectomy resulted in a near total disappearance of binding in both males and females, testosterone treatment resulted in equally high levels of binding in both sexes. Indeed, a high density of AVP receptor binding was observed at all levels of the VLH in both testosterone-treated males and females. These results show that adult female golden hamsters are equally capable as males of expressing high levels of AVP receptor binding in the VLH in response to high levels of testosterone. Together, our results suggest that, while AVP receptor binding within the VLH is sexually different in gonadally-intact animals, these differences are not related to differential responsiveness to testosterone, but rather to a differential production and availability of the hormone.