Sympatho-adrenomedullary system responses to various chronic stress situations

We studied the effects of four different chronic stressors: isolation, crowding, forced swimming and isolation followed by forced swimming, on the level of plasma noradrenaline (NA) and adrenaline (A), both under basal conditions and in response to acute immobilization and cold as additional stressors. None of these chronic stressors changed basal plasma NA and A concentrations. When chronically isolated rats are exposed to immobilization they show significant elevation of plasma NA and A, but cold stress significantly increases only NA level and not the concentration of A. When animals exposed to chronic crowding, forced swimming and isolation plus forced swimming are exposed to immobilization plasma catecholamine also increases, but less in comparison to the chronically isolated rats. Based on these results, it may be concluded that chronic isolation seems to be a stronger stressor for animals than other chronic stressors. Chronic forced swimming stress and crowding seem to be the weakest stressors, if measured by the activity of sympathoadrenomedullary system. However, daily short-term swimming stress seems to attenuate the effect of chronic isolation on the activity of the sympatho-adrenomedullary system. .