SUMMARY
Electrolytic lesions were made in the hypothalamus of 41 Merino ewes which were subsequently observed for 2–16 months.
Ovarian inactivity resulted from bilateral medial and ventral lesions placed immediately posterior to the optic chiasma (four ewes) or immediately anterior to the mammillary body (five ewes). Failure to show oestrus while apparently still ovulating regularly was a feature in another four ewes in which bilateral medial and ventral lesions were placed between the sites already described. Small bilateral lesions in these ventral regions led initially to ovarian inactivity, but final re-establishment of apparently normal reproductive activity in three ewes. Bilateral lesions in regions other than those described above resulted in no apparent change in reproductive activity (eight ewes). Similarly, unilateral or asymmetrical lesions in the remaining 17 ewes failed to affect their reproductive activity.
The results are consistent with the hypothesis that in sheep a region of the median eminence responsible for the production of gonadotrophin-releasing factors requires neural inputs traversing both anterior and posterior hypothalamic areas.
REPRODUCTIVE POTENTIAL OF THE MALE RAT: ENHANCEMENT OF COPULATORY LEVELS FOLLOWING LESIONS OF THE MAMMILLARY BODY IN SEXUALLY NON-ACTIVE AND ACTIVE ANIMALS
