Effect of Age on the Sexual Behaviour of the Male Rat

Abstract

The male rat mating behaviour was studied in four different groups, aged 103-114, 125-164, 450-510 and 573-651 days respectively. The subjects were allowed to mate until they attained a specific criterion of exhaustion. It was found that the animal''s capacity to attain repeated ejaculations increased with age, the youngest subjects being most rapidly exhausted and the oldest ones most resistant against exhaustion. There occurred great changes in the mating pattern with increasing age. The number of intromissions preceding ejaculation was highest in the youngest age group and progressively decreased with age. The response latencies were progressively reduced up to 450-510 days of age but become prolonged in the oldest age group. While the young male copulated with maximal speed immediately after having been presented with the receptive female, the subjects in the two oldest age groups responded by minimal response latencies only in the presence of facilitatory effects from one and two series of copulations. This was interpreted as indicating a heightened threshold in old age for the arousal of the copula-tory response.