[Effect of age on the copulatory behavior of the male rat]

Fifteen male SPF Wistar-Imamichi rats, aged 10, 27 and 44 weeks, that had been raised in the authors' laboratory, were used for the observation of copulatory behavior. Each male was given the opportunity to mate with a proestrous female. During a two hour period, standard measures of copulatory behavior, e.g., mounting, intromission and ejaculation, were documented by a video recording. The following results were obtained; the number of ejaculations in 10-week-old rats, over a two hour period, was 6 to 8. Males showed a subsequent post-ejaculatory interval. The males aged 27 weeks performed 3 to 4 times during the first hour, and then refrained from sexual activity. The copulatory behavior in males aged 44 weeks declined, as compared with that of their 10 and 27 weeks old counterparts.