Abstract
Wild Sika deer (Cervus nippon yesoensis) are seasonal breeders and their reproductive behaviors change annually. Since reproductive activity is regulated by gonadotropins, gonadotro-pic cells (LH and FSH cells) in pituitaries in 19 male and 18 female wild Sika deer, which were collected from Ashoro town in Hokkaido, were investigated by immunohistochemical methods. Gonadotropic cells remarkably changed between August (the end of non-mating season) and October (mating season); their distribution was wider and their immunostaining reactivity was more intensive in October than in August in males and females. We found that gonadotropic cells existed also in the pars intermedia and that these cells showed seasonal changes similar to those in the pars distalis. The significances of such seasonal changes in gonadotropic cells in the wild Sika deer were discussed.
