Many progestin receptor-containing neurons in the guinea pig ventrolateral hypothalamus contain substance P: immunocytochemical evidence

Abstract

Behavioral and neuroanatomical evidence in rats suggests that substance P may mediate hormonally induced sexual receptivity. To determine if progestin receptor-containing neurons in the guinea pig hypothalamus also contained substance P, we used a double antibody, immunocytochemical technique. Ovariectomized, adult guinea pigs were estradiol-primed for one week. Two days prior to perfusion, colchicine was infused into the lateral ventricle. Substance P-immunoreactive neurons and progestin receptor-immunoreactive neurons were found throughout the hypothalamus and caudal preoptic area. However, substance P and progestin receptor immunoreactivity occurred in the same neurons almost exclusively in the ventrolateral area of the hypothalamus, an important site in the hormonal regulation of female sexual behavior in guinea pigs. Within this area, approximately 35% of the progestin receptor-immunoreactive neurons also contained substance P immunoreactivity. These neuroanatomical data are consistent with the hypothesis that substance P may mediate some of the neural actions of progesterone.