Involvement of Activin and Inhibin in the Regulation of Food and Water Intake in the Rat

抄録

The expression of activin and inhibin has been demonstrated in the hypothalamus, but their physiological roles in the brain remain to be elucidated. In the present study, involvement of activin and inhibin in the regulation of food and water intake was examined. Male rats were deprived of food or water for 12 and 60 hr, and mRNA levels of activin/inhibin α, βA and βB subunits in the hypothalamus were estimated by RT-PCR. Gene expression of α subunit transiently decreased at 12 hr of food deprivation, while it did not change during water deprivation. Food and water deprivation for 60 hr increased mRNA levels of βA and βB subunits, respectively. These results indicated that gene expression of each subunit was independently regulated. Injection of activin A (0.5 and 4.0 μg) into the third ventricle decreased food intake. Water intake was suppressed by 4.0 μg, but not 0.5 μg, of activin A. Intracerebroventricular injection of inhibin A (0.5 and 4.0 μg) decreased water intake in a dose dependent manner without affecting food intake, suggesting that inhibin could act independently of activin. Taken together, it is suggested that activin and inhibin take part in the central regulation of nutrient and fluid balance, though further study is needed to determine precise molecular species involved.