Dissociation of androgen-dependent sociosexual behaviors in response to castration in Long-Evans rats

Copulatory behavior and associated social behaviors such as ultrasonic vocalizations and scent marking are reduced in frequency following castration and are restored by exogenous administration of androgens. In the present study, we report the behavior of a subgroup of male Long-Evans rats in which there was a dissociation between the responses of androgen-dependent behaviors to castration. Five weeks after castration, 52% of the males tested (13 of 25) had higher 50 kHz vocalization frequencies than during precastration tests. This group continued to emit vocalizations after castration and actually increased their number of vocalizations over postcastration tests (pretest: 34.5 +/- 4.8 to week 15: 62.8 +/- 10.9/10 min test). The remaining males (n = 12) exhibited a decline in vocalizations (pretest: 29.7 +/- 5.1 to week 15: 6.5 +/- 2.7) that we typically observe in our laboratory. Both groups showed the expected decline in scent-marking frequency over the postcastration tests and were impaired in performance of copulatory behavior. Seminal vesicle and adrenal gland weights did not differ between the two groups. The 25 males were of the same genetic strain as previous animals in our laboratory except that they were born and raised in a different location prior to shipment to our laboratory. Androgens, therefore, may be only one of the possible influences mediating ultrasonic vocalizations.