Effects of diazepam, FG 7142, and RO 15-1788 on schedule-induced polydipsia and the temporal control of behavior.

Although benzodiazepine agonists and inverse agonists have opposite effects on drinking elicited by water deprivation, there is much less information about the effects of these drugs on nonhomeostatic drinking. In this experiment the effects of diazepam (0.3-5.0 mg/kg), a benzodiazepine receptor agonist, and FG 7142 (1.0-9.0 mg/kg), an inverse agonist, were determined on drinking elicited by a FT-60 schedule of food delivery (SIP). Both diazepam and FG 7142 dose-dependently reduced SIP, measured as either licking or volume consumed. In addition, diazepam reduced panel pressing for food, decreased locomotor activity, and changed the time course of each behavior. In contrast, FG 7142 reduced schedule-induced drinking without significantly altering other behaviors. The antagonist RO 15-1788, when given in combination with these drugs, only partially restored the reductions in licking produced by diazepam, but was much more effective in reversing the effects of FG 7142 at doses of the antagonist that failed by themselves to affect responding. The opposite pattern of effects was seen on the volume of water consumed. These effects are discussed in terms of the behavioral and pharmacological specificity of these drugs.