Clonazepam selectively increases saccharin ingestion in a two-choice test

Twenty-two-hour water-deprived rats were trained with a choice between a sodium saccharin solution (0.01% or 0.05%) and water in a 30-min drinking test. The potent benzodiazepine agonist, clonazepam, produced highly significant dose-related (0.1-1.0 mg/kg, i.p.) increases in total fluid consumption. The most important finding was that clonazepam selectively enhanced ingestion of the preferred 0.05% solution, while producing no change in the consumption of water. It did not selectively affect ingestion of the marginally preferred 0.01% solution. These data can be linked to recent evidence that benzodiazepines facilitate positive ingestive reactions elicited by palatable tastes. Together, the evidence indicates that benzodiazepines can selectively affect consumption of preferred solutions through enhancement of positive reactions to palatable tastes. In contrast to the results with clonazepam, the novel compound zolpidem, which binds preferentially to cerebellar-type benzodiazepine sites, failed to affect fluid intake or sweet taste preference. This suggests that hippocampal-type, as distinct from cerebellar-type receptors, may be necessary in the mediation of effects of benzodiazepines on taste-palatability processing and ingestion.