Discriminative-stimulus and time-course effects of kava-kava (Piper methysticum) in rats

Kava-kava is a widely available and used herbal medicine that is not regulated in many countries, including the United States. There are many questions concerning kava-kava's stimulus properties, potential for therapeutic use, and potential for abuse. Although there is evidence that kava may possess some anxiolytic properties, the supplement's mechanism of action and the extent to which it may serve as an alternative to pharmaceutical anxiolytics are unknown. To date, there is no research examining whether kava shares discriminative-stimulus properties with a standard pharmaceutical anxiolytic such as chlordiazepoxide (CDP). The current study compared different doses of kava in two groups of rats trained to discriminate either a high or low training dose of CDP (i.p.). In order to assess time-course effects of kava (p.o.), two tests were conducted per session at 60 (Test One) and 90 (Test Two) min following administration of kava, CDP, or d-amphetamine. Dose-dependent substitution of CDP was found in both training groups. d-Amphetamine did not substitute for either group at Test One, but marginal substitution was found in both groups at the lower doses of d-amphetamine during Test Two. Kava (560 mg/kg) occasioned responding indicative of partial substitution in both groups during Test One and only the low-dose group during Test Two. Several procedural variables that may have influenced the present results are discussed.