Atropine decreases drinking but not feeding and induces less hypothalamic acetylcholine release in diabetic rats

Drinking, feeding and hypothalamic extracellular acetylcholine (ACh) release was measured before and after the administration of several doses of atropine sulfate in streptozotocin (STZ)-diabetic and normal rats. Drinking but not feeding was dose-relatedly decreased by i.p. or intrahypothalamic injections of atropine in STZ-diabetic rats. Hypothalamic ACh release, as measured by microdialysis, increased less (dose-related) in diabetic than normal rats following an i.p. administration of atropine. Ach basal levels were the same in both groups. These results are discussed in terms of a hyperactive hypothalamic cholinergic (muscarinic) system involved in the diabetic polydipsia.