MATERNAL HORMONAL MANIPULATIONS IN RATS CAUSE OBESITY AND INCREASE MEDIAL HYPOTHALAMIC NOREPINEPHRINE RELEASE IN MALE

In previous work it has been shown that adult male, but not female, of fspring of rats that have either been injected with Protamine Zinc Ins ulin on days 15-20 of gestation, or undernourished during the first 2 weeks of gestation, develop significant obesity commencing at about 50 days of age. The present experiment examines the question of whether rats with these two forms of obesity display neurochemical abnormaliti es in areas of the brain known to influence food intake and body weigh t. Twenty-one gauge stainless steel guide shafts were surgically impla nted using standard stereotaxic procedures. One week later 26 ga micro dialysis probes were lowered into the medial hypothalamus. Dialysates collected from male offspring in the two experimental conditions conta in significantly higher norepinephrine (NE) levels than did controls. It would appear that in addition to sharing a similar time course of o nset and a sex dependent expression of obesity, both of these models a re also characterized by elevated medial hypothalamic NE. Since this o besity appears only in males, and at a time when testosterone levels a re rapidly rising in males, and since testosterone has been shown to e levate food intake and body weight in rats, we also investigated wheth er gonadal weights or circulating testosterone levels were differentia lly elevated by our manipulations.