[Changes in plasma prolactin levels during physical exercise in man: effect of preliminary mental activity related to...

1. Eighteen male volunteers, from 19 to 21 years, were studied immediately before and after submaximal exercise (50-70% VO2 max and from 0.30 to 0.50 p.m.). These subjects accomplished from 10 to 11:30 a.m. two kinds of mental work: group A (n = 10) was attending a lecture and group B (n = 8) was sitting for an examination (i.e. mental work associated with emotional stress). 2. Plasma prolactin levels were measured before and after exercise by radioimmunoassay method. Results were compared between these two groups and with control groups C (n = 6) and D (n = 6), at rest from 0.30 to 0.50 p.m., and respectively placed in the same situations as groups A and B prior exercise. 3. Plasma prolactin rose during exercise following mental work as generally observed in exercise. On the contrary plasma prolactin decreased during exercise following an examination but prolactin levels before exercise were significantly higher if stress was prior to exercise. This marked increment in plasma prolactin could be related to stress associated with examination if compared to control groups; the previous emotional stress could inhibit prolactin response to a future excitement.