Influence of mating and intra-uterine oestradiol infusion on peripheral oxytocin concentrations in the sow

Abstract

ABSTRACT Oxytocin concentrations were measured radioimmunologically in sows on the day of standing oestrus over a 6-h period (controls, n=6) or 1 h before and 5 h after mating (n=5) or transcervical infusion of either 100 ml saline (0·9% (w/v) NaCl, n=7) or saline plus 10 μg oestradiol (simulation of seminal oestrogens, n=5). In the controls, oxytocin was low, at around 1·0 pmol/l, throughout the investigation period. Similarly, saline infusion did not lead to a noticeable change in oxytocin concentrations in six out of seven sows. In one sow, however, infusion led to a maximum of 86 pmol/l at 1 min after infusion. Oestradiol led to no immediate increase in oxytocin concentrations. Later in the post-treatment period (2–5 h) they were only slightly increased (1 pmol/l vs 3 pmol/l). All mated sows reacted with a rapid and clear increase in oxytocin. Maximal concentrations (42·0±5·1 pmol/l; mean ± s.e.m.) appeared 2 min after the onset of ejaculation. Clearly increased concentrations were found for 40 min. It was concluded that mating specifically leads to a rise in oxytocin, probably due to both mechanical and pheromonal stimuli provided by the boar. Journal of Endocrinology (1990) 126, 361–365