Post-ejaculatory vocalization in castrated rats treated with various steroids.

Five groups of rats were observed for sexual behavior as intact subjects and in the 3 weeks following castration. Particular emphasis was placed upon ultrasonic vocalization recorded during the refractory period (RP) following ejaculation. All rats received daily injections (100 mug test steroid + 100 mug dihydrotestosterone propionate, DHTP) from the day of castration. Treatment groups were: Testosterone propionate (TP) + DHTP, N = 5; 19-hydroxytestosterone propionate (19HTP) + DHTP, N = 6; Oestradiol dipropionate (OP) + DHTP, N = 5; DHTP (200 mug/day), N = 6; Vehicle only, N = 7. Ejaculation and normal RPs were maintained with TP, 19HTP and OP treatments. In rats treated with DHTP alone or vehicle only ejaculatory ability declined and RPs increased in length. Ultrasonic vocalization was normal in all rats except those treated with OP, where it was either reduced or absent. In Week 4 treatments in TP + DHTP and OP + DHTP groups were reversed. During Weeks 5-7 vocalization was gradually restored in rats that previously received OP and partially inhibited in animals previously treated with TP. These results indicate that; (1) vocalization may not be dependent on the presence of testicular androgens and, (2) OP has a gradual inhibitory effect on vocalization when given at high doses and this effect is reversible.