Effects of low dose capsaicin (CAP) on ovarian follicle development in prepubertal rat

Abstract

This study was carried out to investigate effects of low-dose capsaicin (CAP) treatment on follicular development in prepubertal rat ovaries. Eighty female Sprague-Dawley rats (21 days old) were randomly divided into 3 groups according to treatment: whereas the first group received no treatment (control A. n = 5 x 4), rodents of the second group (group CAP, n = 10 x 4) were subcutaneously injected with CAP diluted with solvent (10% ethanol, 10% Tween 80, and 80% distilled water) at 0.5 mg/kg/d and those of the third group were treated with vehicle only (control B. n = 5 x 4). After euthanasia of 10 controls (5 from the group A and 5 from the group B) and 10 CAP-treated rats by ether inhalation at 6, 9, 12 or 15 days, apoptosis was investigated in ovarian follicles by the TUNEL method and by evidence of active 3 caspase expression throughout immunohistochemistry and western blot while cell proliferation was assessed by Ki67 immunohistochemistry. Follicular atresia was observed in the antral follicles (types D and E) of all ovary sections but, in the CAP-treated group, the apoptotic indexes coupled to atresia were significantly lower compared to controls particularly on Days 9 and 15 and the active caspase 3 accumulation in cytoplasm was also significantly depressed. By contrast, follicle proliferation indexes were exacerbated in treated rodents compared to controls on days 12 and 15. The results indicate that the administration of low dose CAP interferes in the ovarian follicular development by partially inhibiting atresia-coupled apoptosis and promoting cell proliferation, probably throughout the release of some neuro-peptides present in the capsaicin-sensitive sensory neurons.