Effects of rostro-dorsal deafferentation of the hypothalamus on the onset of puberty in female rats.

Rostro-dorsal deafferentation of the hypothalamus by means of the preoptic-roof cut was performed in immature female rats at 17, 21 or 25 days of age, and the onset of puberty was recorded in these and in sham-deafferentated females. A significant delay of vaginal opening and the first ovulation was found following transection of the stria terminalis and fornix system on day 17 or day 25, whereas treatment on day 21 did not influence the onset of puberty. The findings may be explained on the basis of former results obtained after lesioning of the medial amygdala or ventral hippocampus at different ages. They suggest that the puberty-advancing effect of hypothalamic lesions does not depend upon the interruption of afferents from extrahypothalamic structures, but may be caused by the destruction of hypothalamic neurons and/or intrahypothalamic fibres.