The anxiogenic-like effects of pentylenetetrazole in mice treated chronically with carbamazepine or valproate.

The chronic effects of carbamazepine administration (5, 10, 20 mg/kg i.p. daily for 14 days) on the anxiogenic response to pentylenetetrazole were studied in the light/dark aversion test. In mice, these effects were compared with those of sodium valproate (100, 200 and 300 mg/kg i.p.), a putative anxiolytic drug, and lorazepam (0.025, 0.05 and 0.10 mg/kg i.p.), a well-established anxiolytic drug. The results showed that the anxiogenic-like behavior induced by subconvulsant doses of pentylenetetrazole (15 mg/kg i.p.) was antagonized by the chronic administration of lorazepam as well as sodium valproate, a GABA agonist. In fact, the increased aversion of mice for the light compartment of the light/dark box was reduced. Carbamazepine failed to significantly alter the anxiogenic-like behavior of mice. These findings provide further evidence for the absence of anxiolytic properties of carbamazepine and for a behavioral anxiolytic profile of valproate similar to that of benzodiazepines.