Pentobarbital and ketamine suppress serum concentrations of sex hormones in the female rat

Purpose. To investigate the potential effects of pentobarbital and ketamine on serum concentrations of sex hormones, the present study was performed using pregnant mare serum gonadotropin (PMSG)-primed cyclic female Sprague-Dawley rats. Methods. Pentobarbital sodium (37 mg·kg⁻¹, i. p.) or ketamine-hydrochloride (229 mg·kg⁻¹, i. m.) was injected 2 and 3 days after PMSG treatment. At 0, 1, 2, 3, 4, and 5 days after PMSG treatment, sera were collected by cardiac puncture. The serum concentrations of progesterone (P₄), testosterone (T), and estradiol-17β (E₂) were determined by radioimmunoassay. Results. The serum concentrations of P₄ tended to be lower in both the pentobarbital- and the ketamine-treated groups compared with the control group. Significant differences were found on days 3 and 4 after pentobarbital and on days, 1, 4, and 5 after ketamine administration. Serum concentrations of T were also suppressed in both the pentobarbital and the ketamine-treated groups, whereas E₂ concentrations decreased only in the ketamine-treated group. Conclusion. Pentobarbital and ketamine decrease serum sex hormone concentrations in PMSG-primed female rats. Received: March 18, 2000 / Accepted: June 26, 2000