Intravenous self-administration of gamma-hydroxybutyrate (GHB) in baboons

Background: Abuse of gamma-hydroxybutyrate (GHB) poses a public health concern. In previous studies, intravenous (IV) self-administration of GHB doses up to 10. mg/kg was not maintained in non-human primates under limited-access conditions, which was inconsistent with the usual good correspondence between drugs abused by humans and those self-injected by laboratory animals. Methods: Self-administration of GHB was studied in 10 baboons using procedures standard for our laboratory to assess drug abuse liability. Each self-injection depended on completion of 120 or 160 lever responses. Sessions ran continuously; a 3-h timeout limited the number of injections per 24. h to 8. Self-injection was established at 6-8 injections/day with cocaine (0.32. mg/kg/injection) prior to substitution of each GHB dose (3.2-178. mg/kg/injection) or vehicle for 15. days. Food pellets were available 24. h/day. Results: GHB maintained significantly greater numbers of injections when compared to vehicle in 6 of the 9 baboons that completed GHB evaluations that included 32. mg/kg/injection or higher. The baboons that self-administered GHB at high rates were ones for which GHB was the first drug each had tested under the 24-h/day cocaine baseline procedure. Self-injection of the highest doses of GHB decreased food-maintained responding. Conclusions: High-dose GHB can function as a reinforcer in non-human primates under 24-h access, but self-administration history may be important. The findings are consistent with the demonstrated abuse liability of GHB in humans, and remove GHB as an exception to the typical good correspondence between those drugs abused by humans and those self-administered by nonhuman primates.