LESIONS OF THE SUPRACHIASMATIC NUCLEUS DO NOT DISTURB SEXUAL ORIENTATION OF THE ADULT MALE-RAT

An enlarged suprachiasmatic nucleus (SCN) has been found earlier in a group of homosexual men, as compared to heterosexual controls. In orde r to assess a possible relationship between the SCN and sexual orienta tion, the present study was undertaken to investigate whether the rat SCN might play a role with respect to the expression of sexual orienta tion. Sexual orientation was measured in partner preference tests as t he percentage of time spent in the vicinity of sexually active male an d female incentives, that were separated from the experimental animal by a wire mesh. The results show that established patterns of sexual o rientation towards female incentives by the adult male rat are not inf luenced by SCN-lesions. Disturbances in circadian rhythmicity of activ ity in SCN-lesioned animals did not affect this conclusion.