REM sleep deprivation facilitates the estrogen effect on heterotypical sexual behavior in male rats

Gonadectomized male rats were submitted to REM sleep deprivation (REMd) for 120 hr and their hetero and homotypical sexual response to estradiol benzoate (EB) was tested. Subjects (Ss) receiving 20 micrograms EB showed lordosis quotients (LQ) twice as high as those receiving 10 micrograms EB and at the same time the LQs in these groups were higher than in the non-REMd groups. Gonadectomized-adrenalectomized control Ss showed the highest levels of lordosis throughout the experiment. REMd by itself does not produce lordosis response. The results indicate that the brain structures underlying this behavior in males are probably similar to those in females, since REMd increases lordosis in both cases. The lack of homotypical sexual behavior normally observed in gonadectomized male rats does not seem to be affected by this treatment. The issue of adequate controls for REMd experiments is discussed.