Purinergic control of anxiety: direct behavioral evidence in the rat.

The purines inosine and hypoxanthine have been implicated in neurobiological effects associated with benzodiazepine-receptor occupancy, and may be endogenous ligands of benzodiazepin receptors. The behavioral effects of purinergic activation upon anxious behaviors have been less well characterized and understood. We present evidence that purinergic stimulation is sufficient to produce an operationally defined conditioned anxiety response, and that the effect is specific to the benzodiazepine receptor. These findings suggest anxiogenic potency for purines, which may be associated with their normal behavioral and motivational mode of action.