MALES LOCATED CAUDALLY IN THE UTERUS AFFECT SEXUAL-BEHAVIOR OF MALE-RATS IN ADULTHOOD

It has been suggested that the sexual differentiation of female rats i s affected by androgens from male fetuses in the uterine horn (intra-u terine position phenomenon). Effects of adjacent males, as well as of males located caudally in the uterus have been reported. The present s tudy investigated whether male rats, like females, are affected by the presence of either caudal or adjacent male littermates. When tested i n adulthood for sexual behavior, males that had male fetuses located c audally in the uterine horn showed shorter latencies to the first moun t or intromission and shorter latencies to ejaculation, and exhibited more mounts and intromissions per minute than males that lacked caudal male siblings in the uterus. The presence of adjacent males did not s ignificantly affect the parameters studied in this experiment.