The Effect of Corticomedial Amygdaloid Lesions on Prolactin Secretion in Male and Female Rats*

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Abstract
The influence of corticomedial amygdaloid lesions on circulating PRL levels was examined in male and female rats. In ovariectomized female and intact male rats, the plasma PRL levels did not vary over a 24-h period, and lesions of the corticomedial amygdala did not alter this pattern. Castrated male rats had similar morning and afternoon PRL values and here again lesions did not alter this pattern. The injection of 0.5 nig polyestradiol phosphate (PEP) into ovariectomized animals 1 week before sampling induced a PRL surge at 1700 h which was markedly decreased by corticomedial amygdaloid lesions. The basal PRL levels observed at 1100 and 0400 h in these animals were not altered by the lesion. In castrated male rats, basal plasma PRL levels were significantly increased (P < 0.05) by the injection of PEP compared to levels in noninjected controls. Corticomedial amygdaloid lesions did not alter the estrogen-induced increase in basal serum PRL in these animals when the sample was taken at 1700 h, but significantly increased the 1100 h value (P < 0.05). The injection of 1 mg testosterone propionate/day for 7 days into ovariectomized animals induced an afternoon PRL surge similar to that observed after estrogen injection; however, amygdaloid lesions did not alter the testosterone- induced PRL afternoon surge. The administration of 1 mg dihydrotestosterone/day did not alter serum PRL values. The data suggest that the corticomedial amygdala can modulate steroid-induced PRL secretion. (Endocrinology106: 1665, 1980)