Precocious ovarian stimulation following hypothalamic and amygdaloid lesions in rats

Abstract

The effects of neural lesions on the functional development of the reproductive system were studied in prepubertal female rats. Small electrolytic lesions were placed bilaterally in 66 female rats at 18–20 days of age; 42 littermates served as controls, and 7 rats were blank-operated. All animals were weighed two to three times a week and examined daily for vaginal opening. At 33 days of age the uteri, ovaries and adrenals were weighed and prepared for histological study. All brains were examined histologically for lesion localization. Lesions in the anterior hypothalamus or in the medial portion of the amygdaloid complex were associated with precocious ovarian stimulation. With the exception of one lesion in the basal septum and one in caudate-putamen, bilaterally symmetrical lesions in other parts of the brain and asymmetrical lesions have been ineffective. These results are compatible with an anterior hypothalamic mechanism involved in the inhibition of gonadotropin secretion and suggest the inclusion of the medial portion of the amygdaloid complex in this mechanism.