Characterization of rat exploratory behavior using the exploration box test.

A method to measure various aspects of exploratory behavior was further characterized using standard pharmacological treatments known to induce anxiety, or anxiolysis, or locomotor activation. FG 7142, an anxiogenic beta-carboline, induced a dose-dependent reduction in the rat exploratory behavior. A single FG 7142 (20 mg/kg) treatment before behavioral testing had a carry-over effect on rats' behavioral performance on the two subsequent days. When FG 7142 (20 mg/kg) was administered during five consecutive days before behavioral testing, its anxiogenic-like effect first deepened, but waned off by the fifth session. Diazepam at the dose of 0.5 mg/kg had no effect of its own, but blocked the anxiogenic-like effect of FG 7142 (10 mg/kg) treatment. At a higher dose (1 mg/kg), diazepam treatment reduced exploratory behavior, but this effect was not carried over to the drug-free sessions on the subsequent day. Buspirone and gepirone (both 1 mg/kg), the 5-HT1A receptor agonists, had no effect. D-Amphetamine, a locomotion-enhancing drug which has anxiogenic-like properties in several tests of exploratory behavior, increased the activity of rats at the dose of 0.5 mg/kg, but at the dose of 1 mg/kg the only effect was a reduction in the number of rearings: this effect was not carried over to the subsequent retest. On the basis of the results described in this article and elsewhere, we suggest that this technique can be useful for separating a true anxiogenic drug from other compounds which influence exploratory activity.