Experimental induction and termination of acute psychological stress in human volunteers: effects on immunological, neuroendocrine, cardiovascular, and psychological parameters

The present research investigated the effects of controlled experimental manipulations of stress on biological and psychological reactions. Fifty young adult male volunteers were exposed to a 12-min period of stress induced by the threat of an unavoidable, painful electric shock. A 12-min period without this threat preceded or followed the stress period. Blood was drawn during the 4th and the 12th minute of each period. Anticipatory threat led to significant elevations in the proportions and cytotoxic activity of natural killer (NK) lymphocytes, plasma epinephrine levels, pulse rate, and reported level of tension, and to a reduction in the CD4/CD8 ratios. The no-threat period induced a return to baseline values for epinephrine, pulse rate, and tension, and lower than baseline levels for cytotoxic activity of NK lymphocytes, within a similarly short time span. The findings underline the rapidity with which physiological changes may transpire in the course of a brief and acute period of psychological stress, and the rapidity of their reversal upon relief from the stressor.

Restraint stress-induced changes in lymphocyte subsets and the expression of adhesion molecules

The effect of restraint stress on the distribution of lymphocyte subsets were studied in young BALB/c male mice. Loss of whole body weight, a reduction in the weights of spleen and lymph nodes, and higher levels of serum corticosterone were evident after a single continuous restraint period of 16-18 h. Tissue sections of spleens from restrained animals revealed erythrocyte depletion in the contracted red pulp. Furthermore, there was a significantly higher proportion of CD4+, but not of CD8+, lymphocytes in the spleen. The proportion of the CD4+ subset was markedly diminished in peripheral blood, whereas no changes were detected in lymph nodes. Restraint resulted in enhanced allogeneic mixed lymphocyte reactivity and in altered expression of some CD4+, but not CD8+, splenocyte adhesion molecules (CD44, LFA-1 and VLA-4). Removal of circulating corticosteroids by surgical adrenalectomy abolished the restraint-induced changes in lymphocyte adhesion molecule expression. The findings suggest that the observed differences in lymphocytes subset distribution of lymphoid organs may be due to changes in the pattern of adhesion molecule expression.