CENTRAL VS PERIPHERAL METABOLIC CONTROL OF ESTROUS CYCLES IN SYRIAN-HAMSTERS .2. GLUCOPRIVATION

Estrous cycles in Syrian hamsters are inhibited by food deprivation or treatment with pharmacological inhibitors of intracellular glucose ut ilization (glucoprivic treatments). These same metabolic challenges in crease neural stimulation in areas of the caudal brain stem thought to be involved in detection of metabolic signals. Experiment 1 was desig ned to examine whether vagally transmitted signals are important for g lucoprivic effects on estrous cycles and on neural stimulation in the caudal brain stem. Vagotomized or sham-operated hamsters were treated with 2-deoxy-D-glucose (2-DG) at a dose known to decrease cellular glu cose utilization and inhibit estrous cycles (1,750 mg/kg). Vagotomized and sham-operated hamsters did not differ significantly in incidence of 2-DG-induced anestrus or in neural stimulation in the caudal brain stem, but the effects of 2-DG on estrous cycles and neural stimulation appeared to have been attenuated in vagotomized hamsters. In experime nt 2, hamsters were injected intracerebroventricularly with 2-DG or gl ucose at doses that did not induce anestrus when injected systemically (125 and 250 mg/kg). Groups treated with intracerebroventricular inje ctions of 2-DG showed a significantly higher incidence of anestrus tha n those treated with glucose. In experiment 3, effects of systemic inj ections of 2-DG were prevented by prior injection of glucose on fructo se at the same concentration, indicating that 2-DG acts via effects on glucose metabolism, rather than via a nonspecific pharmacological eff ect or generalized stress response. Results of these experiments and t hose reported elsewhere [J. E. Schneider, A. J. Hall, and G. N. Wade. Am. J. Physiol. 272 (Regulatory Integrative Comp. Physiol. 41): R400-R 405, 1997] are consistent with the notion that central glucoprivation is sufficient, whereas peripheral lipoprivation is not critical, for m etabolic effects on estrous cycles.