The effect of corticomedial amygdaloid lesions on serum PRL levels was investigated in adult female rats neonatally androgenized (NA) on day 3 of life with 1.25 mg testosterone propionate. NA animals exhibiting constant vaginal estrus were studied at 4 and 6 months of age in a series of three experiments. Basal (1100 h) PRL levels were elevated in adult NA females compared to levels in control females that were ovariectomized and estrogen primed. Four-month-old NA rats, decapitated at 1100 and 1700 h, had statistically significant diurnal fluctuations in serum PRL levels (118.1 ± 14.8 and 207.8 ± 13.7 ng/ml, respectively). Ablation of the corticomedial amygdala 1 month before sacrifice significantly reduced these elevated levels. A second group of NA females, decapitated at 1100 h at 6 months of age to determine if the elevated basal PRL levels in NA rats were affected by increasing age, had high serum PRL levels, similar to those of younger NA rats, which were significantly reduced by corticomedial amygd...