Effects of prolactin-secreting tumour on copulatory behaviour in male rats

The effect of the transplantable prolactin- and ACTH-secreting tumour 7315a on male copulatory behaviour was investigated. Castrated tumour-bearing rats implanted with testosterone-filled capsules exhibited significantly longer latencies to first mount or intromission and to ejaculation than castrated control animals. In contrast to the number of intromissions, the number of mount before ejaculation of the tumour-bearing rats was considerably increased. However, when castration was carried out in addition to adrenalectomy, the differences in copulatory behaviour between tumour-bearing rats and control rats were no longer present. During the last tests for copulatory behaviour the tumour-bearing rats had serum prolactin concentrations or more than 4000 ng/Ml while control rats had less than 100 ng/ml. Plasma testosterone levels produced by silicone elastomer capsules were neither affected by the presence of the tumour nor by adrenalectomy. It was concluded that hyperprolactinaemia does not suppress the copulatory behaviour of adrenalectomized rats.