Age Differences in the Diurnal Periodicity of Male Sexual Behavior

Abstract

The diurnal variation of sexual activity in two age groups of male rats was investigated. In one group of 38 animals the age was 5-7 months, in the other group the age was 14-16 months. No significant difference in the performance during the active phase was seen. In the passive phase, however, 48.8% of the older animals did not ejaculate while the corresponding percentage for the younger rats was 10.8%. This highly significant decrease in the number of ejaculating animals was interpreted as depending on changes in the central nervous system accompanying age and intensifying the effect of inhibitory unconditioned or conditioned stimuli.