Effects of cocaine self-administration on plasma corticosterone in rats: relationship to hippocampal type II glucocorticoid receptors.

1. The effects of chronic (i.e., 30-day), high-dose (i.e., 1.0 mg/kg/infusion) intravenous cocaine self-administration and non-contingent infusions of cocaine and saline on plasma corticosterone and hippocampal Type II glucocorticoid receptors (GR) were investigated in adult male Wistar rats implanted with indwelling jugular catheters using a self-administration/yoked infusion triad design. 2. In self-administering rats and rats receiving yoked infusions of cocaine, basal corticosterone measured 24 hours after the experimental sessions was reduced relative to yoked-saline controls and to pre-acquisition values. 3. In contrast, corticosterone measured immediately following the self-administration sessions remained unaltered throughout the course of the experiment. 4. In cocaine self-administering rats, the effects on basal corticosterone were observed earlier than they were in rats receiving yoked infusions of cocaine. 5. The effects of self-administered and yoked cocaine were associated with statistically non-significant increases in hippocampal GR density relative to yoked-saline controls as measured by Western blot analysis using the anti-GR monoclonal antibody BuGR2.