BETA-ENDORPHIN, BUT NOT SUBSTANCE-P, IS INCREASED BY ACUTE STRESS IN HUMANS

The role of neuropeptides in the psychoneuroendocrinological stress re sponse is largely unknown. In this study the effect of acute psycholog ical stress on beta-endorphin and substance-P plasma concentrations wa s investigated and further the effect of different anxiety levels or c ontrol attributions on beta-endorphin or substance-P levels was determ ined. Blood samples were obtained from 47 inexperienced tandem-parachu tists 2 h before, immediately after, and 1 h after a parachute jump an d plasma concentrations of beta-endorphin and substance-P were analyse d. Anxiety levels and control attributions were assessed by psychometr ic scales. Whereas substance-P concentrations seemed to be unaffected by the jump stress, there was a transient but significant increase in beta-endorphin levels immediately after jumping. However, subjects hig her in state-anxiety at the point of jumping (exit) displayed higher s ubstance-P values at all three time points compared to the ''low anxie ty'' jumpers. In addition, stress-induced beta-endorphin secretion was dependent on subjective control attributions.