The effect of raphe nuclei lesions on the rat ovarian cycle.

The effects of lesions of the median raphe or dorsal raphe nuclei on ovarian cycle were studied in rats. Lesions involving raphe nuclei decreased forebrain 5-HT and 5-hydroxyindole acid (5-HIAA) concentrations. Rats with lesions of the raphe showed prolonged estrous phase as well as an increase in both the eosinophilic index and karyopycnotic index of the vaginal smears. Histological examinations revealed that lesions of both the dorsal and median raphe produced marked increase in the number of maturing and mature follicles as well as an increase in corpora lutea. The increase in uterine weight was also observed. Present results indicate that lesions of the ascending 5-HT neurons stimulate ovulation and cause an increase in the estrogenic activity. Thus, the 5-HT neurons of the raphe nuclei seem to inhibit ovulation probably due to inhibiting of the hypothalamic releasing hormones.