Cholinergic and dopaminergic blocking agents modulate water intake elicited by deprivation, hypovolemia, hypertomicity and isoproterenol.

In order to identify and differentiate separate components of an overall drinking system on neurochemical grounds, a few neuropharmacological blocking agents, already shown to affect the mediation of some thirst-related behaviors, were tested against a wide range of manipulations that elicit drinking behavior. Peripheral injections of scopolamine, an anticholinergic agent, or haloperidol, a catecholamine blocking agent with pronounced antidopaminergic actions, substantially reduced the water intake of rats induced to drink by periods of deprivations or by subcutaneous injections of either hypertonic saline, polyethylene glycol, or isoproterenol. When a combined injection of both scopolamine and haloperidol was given, hypovolemic and isoproterenol-induced drinking were about entirely eliminated but salt-aroused or deprivation-induced drinking were not totally abolished. In control studies, eating behavior elicited by either food deprivation or peripheral injection of 2-deoxy-d-glucose was not affected by these blocking agents. These experiments suggest that activation of cholinergic and dopaminergic neurons within central thirst-related systems are important physiological events underlying drinking behavior.