EFFECT OF CHRONIC STRESS ON THE SYMPATHETIC COMPONENT OF THE RAT THYMUS

It is well known that different stressing agents, such as sound exposu re, rotation, intermittent shock or forced immobilization, produce alt erations of the immune system. Having in mind recent studies about the effects of stress on the immune system, we investigated whether chron ic stress induced by a forced swimming procedure alters the sympatheti c component of the autonomic nervous system in the rat thymus. For tha t purpose we exposed AO strain male rats, 22 days old, to a swim test during 21 days. The experimental animals were divided into two groups, and sacrificed by decapitation, the first group the day after the las t treatment, and the second group one month later. Their thymuses were used for determination of the distribution and density of sympathetic nervous profiles, as well as the concentrations of noradrenaline (NA) , dopamine (DA), and serotonin (5-HT). When compared with controls, th e results for the first group showed that chronic stress did not affec t the distribution of sympathetic nervous profiles, but significantly reduced the density and intensity of fluorescence,as well as the conce ntrations of NA, DA and 5-HT. The results for the second group showed the same changes but of lower degree. These changes indicate that chro nic stress might influence thymus development and T cell maturation by altering the sympathetic component, and that these altrations persist for one month.