Sex differences in open-field behavior in response to the beta-carboline FG 7142 in rats.

Sex differences in animal models of anxiety and depression that employ external stimuli have been previously reported. This study examined the effect of gender on pharmacologically induced anxiety in rats coupled with novel handling, injection, and activity in an open-field test. The anxiogenic compound FG 7142 significantly decreased male open-field exploratory at 5, 10, and 20 mg/kg, while rearing behavior was decreased only at the 20 mg/kg dose. Female rats were more resistant to the effects of FG 7142 on open-field exploratory behavior, decreasing open-field activity, and rearing behavior only after the administration of a dose of 40 mg/kg. In addition, a significant sex difference was observed in the open-field activity of rats injected with the vehicle control. Male rats were less active but showed a similar level of rearing behavior when compared to female rats. The greater sensitivity of male rats to the activity-suppressant effects of FG 7142 could explain the sex differences observed in several other animal models of anxiety and depression.