Effects of PVN lesions on the responsiveness of female rats to estradiol.

Previous research has shown that the paraventricular nucleus of the hypothalamus (PVN) is an important site of action for the effects of estradiol on feeding behavior. The recent finding that estrogenic stimulation of the PVN lowers food intake without inducing lordosis suggests that the effects of estradiol on feeding and sexual behaviors are organized separately within the brain. Whether the effects of estradiol on food intake can be attenuated by PVN lesions is therefore a question of practical and theoretical interest. In this experiment we examined the behavioral responsiveness of females with PVN lesions to peripheral treatment with estradiol. 32 adult, female rats received either bilateral or sham lesions of the PVN. All subjects were ovariectomized 2 weeks after the lesion. 2 Weeks following ovariectomy, half of the animals were injected with 2 micrograms of estradiol benzoate (EB) for 3 days, and half were injected with the oil vehicle. 10 days later, the treatment conditions for each subject (oil or EB) were reversed. Histological analysis indicated that 9 females had bilateral lesions of the PVN and 4 had bilateral lesions of the dorsomedial nucleus of the hypothalamus (DMN); 11 animals received sham lesions. Compared with oil treatment, EB injections significantly lowered water intake and body weight gain in all groups. However, food intake was suppressed in the DMN and sham but not in PVN-lesioned females. In addition, statistical analyses indicated that EB treatment induced similar levels of female sexual behavior in all groups. Thus, PVN lesions did not interfere with the ability of estradiol to stimulate lordosis.(ABSTRACT TRUNCATED AT 250 WORDS)