ENHANCED FLUID INTAKE BY RATS AFTER CAPSAICIN TREATMENT

These studies examined stimulated fluid intake by rats in which vagall y mediated signals of gastric distension were blunted by systemic trea tment with the neurotoxin capsaicin, as verified by the loss of cholec ystokinin-induced inhibition of feeding. After overnight food deprivat ion, intake of a 10% sucrose solution by capsaicin-treated rats was gr eater than that by control rats. Similarly, capsaicin-treated rats dra nk more water than did control rats when stimulated by plasma hyperosm olality after intraperitoneal administration of hypertonic NaCl or by isosmotic hypovolemia after subcutaneous administration of a hyperonco tic colloidal solution. Finally, during chronic administration of the mineralocorticoid deoxycorticosterone acetate, capsaicin treated rats consumed more concentrated saline than did control rats. In all tests, intakes by capsaicin-treated rats were significantly greater than tho se by control rats within 5-15 min. These results suggest that early s ignals of gastric distension, such as those that occur during normal e pisodes of food, water, or NaCl intake, may modulate ongoing ingestion and that, with the attenuation of such general inhibitory signals, in gestion continues until gastric distension becomes larger and/or later postgastric signals are detected.