Sex differences in the effects of dexamethasone phosphate on behavior in rats.

The effect of dexamethasone phosphate (DEX) administered in rats' drinking water on running activity and open field behavior was investigated. In Experiment 1 males were given DEX continuously from either five days or one day prior to and throughout testing. Only 5 day treatment significantly increased running wheel activity. DEX had no significant effect on males' 4 day open field activity, but significantly reduced open field and home cage defecation. In Experiment 2 females given DEX defecated significantly more in the open field than controls. This effect on females does not appear to be due to a general metabolic change, since DEX females, like males, defecated significantly less than controls in the home cage. Females' open field activity was not significantly affected. Weight loss and plasma corticosterone analysis confirmed the effectiveness of the dosage used. There appears to be a sex difference in the effects of DEX on open field defecation, possibly due to interaction with gonadal hormones.