GLUCOPRIVIC TREATMENTS THAT INDUCE ANESTRUS, BUT DO NOT AFFECT FOOD-INTAKE, INCREASE FOS-LIKE IMMUNOREACTIVITY IN THE AREA POSTREMA AND NUCLEUS OF THE SOLITARY TRACT IN SYRIAN-HAMSTERS

Animals make a wide variety of physiological and behavioral adjustment s in order to maintain caloric homeostasis. For example, most animals increase food intake when the availability of cellular metabolic fuels is low. The area postrema (AP) and adjacent, reciprocally-innervated nucleus of the solitary tract (NTS) are important brain areas for meta bolic control of food intake in rats. However, in Syrian hamsters, foo d intake is not affected by decreases in metabolic fuel availability s uch as those that occur with food deprivation or with pharmacological inhibitors of metabolic fuels. Hamsters make other adjustments that co nserve energy when the availability of metabolic fuels is low. Estrous cycles are inhibited by treatment with a high dose of 2-deoxy-D-gluco se (2DG), a drug that inhibits cellular glucose utilization, but not b y treatment with methyl palmoxirate (MP) a drug that inhibits fatty ac id utilization. Recent data suggest that the AP/NTS is critical for th e effects of glucoprivation on estrous cycles. Lesions of the AP/NTS p revent 2DG-induced anestrus. If the AP/NTS is involved in anestrus ind uced by glucoprivation, it might be predicted that glucoprivic treatme nts that induce anestrus would change patterns of neural activation, a s measured by FOS-like immunoreactivity (FOS-li), in the AP/NTS. We ex amined FOS-li in females that were either food deprived or fed ad libi tum, and in females treated with 2DG, MP or the appropriate vehicle. F OS-li was increased in the AP/NTS only in hamsters food deprived or tr eated with 2DG, the two treatments that induce anestrus but have no ef fect on food intake. These results are consistent with the notion that metabolic control of estrous cycles involves detection of decreases i n the availability of metabolic fuels in the AP/NTS.