Distribution of the vanilloid (capsaicin) receptor type 1 in the capsaicin treated rat ovaries on different sexual development periods

Abstract

The intra-ovarian expression of the vanilloid receptor type 1 (VR1) was investigated in the present study on rats chronically treated with low dose capsaicin (CAP) according to the sexual development periods. Ovaries were removed at the puberty (42 day old), at the postpuberty (56 day old) or in adult stage (70 day old) from female Sprague Dawley rats receiving daily subcutaneous injections of capsaicin (1 mg/kg/d) diluted into 10% ethanol, 10% Tween 80, 80% distilled water (CAP group), or treated only with the vehicle (VEH group) or not treated (C group) (n = 10 in each subgroup) and tissue samples were processed for conventional histology and for immunohistochemistry using the Streptavidin-Biotin Peroxidase method and a rabbit polyclonal anti-VR1 primary antibody. Serum gonadotropin and sexual steroid concentrations were determined in parallel by commercial ELISA kits. Whatever the sexual development state, the VR1 expression was evidenced in the cytoplasm of various ovarian cell types such as the granulosa, interstitial and luteal cells as well as theca cells at a lesser extend and appeared independent from a hormonal control and from capsaicin treatment. On the other hand, the number of developing follicles has increased in ovaries from the capsaicin treated rats whereas the FSH and LH secretion appeared to be constantly strengthened during the sexual development periods and the ovarian sexual steroid production was globally markedly decreased. Nevertheless, the vehicle injections have also interfered with the hormonal control with highly sustaining the progesterone production. These results showed the constitutive expression of the VR1 in rat ovaries and the positive effects of a chronic capsaicin treatment on the proliferating phases of the follicle development but further studies are required for identifying the specific actions of the drug.