Anxiolytic effect of indole-3-pyruvic acid (IPA) in mice

In an elevated plus-maze indole-3-pyruvic acid (IPA, 100-200 mg/kg), an endogenous metabolite of tryptophan, possesses in mice an activity typical of anxiolytics. IPA increased the ratio of the number of entries into open arms over the total number of entries into open and closed arms and the time spent in open arms. Similar effect was observed for diazepam, a standard anxiolytic. Pretreatment with IPA attenuated the anxiogenic effect of caffeine (50 mg/kg) and 3-hydroxykynurenine (1.2 micrograms, i.c.v.) but not that of pentylenetetrazole (10 mg/kg), or phenylethylamine (5 and 10 mg/kg). Pretreatment with IPA (50-200 mg/kg) did not attenuate pentylenetetrazole- or phenylethylamine-induced seizures in contrast to diazepam which prevents both types of seizures. The data suggest that IPA is an endogenous anxiolytic with novel profile.