Naloxone-induced hypodipsia: a CNS mapping study.

Opiate antagonists have been shown to reliably attenuate drinking behavior. Recent research points to a central site of action for this antidipsogenic effect. To pursue this issue of site specificity, naloxone, a specific opiate antagonist, was delivered into a number of discrete subcortical areas in 23 hour water-deprived rats. Water intake was measured at 5, 15, 30 and 60 minutes post drug injection. Compared to saline control injections, naloxone reliably depressed water intake, in a dose-related manner, in lateral hypothalamus, preoptic area and zona incerta. Previous research has repeatedly implicated these areas in drinking behavior. Placements which were not generally effective included lateral ventricle, nucleus accumbens, substantia nigra and cortex/corpus callosum. Latency to drink was never affected by any dose of naloxone injected into any site, suggesting an opioid influence on mechanisms involved in termination and/or maintenance rather than on initiation of drinking.