Accumulation of adrenaline in sympathetic nerve endings in various organs of the rat exposed to swimming stress.

Swimming produced a marked increase in adrenaline content, but produced no change or slight decrease in noradrenaline content in the heart, spleen and submaxillary gland of the rat. Pretreatment with desmethylimipramine abolished the swimming-induced increase in adrenaline in the three organs. It was also found that the administration of 6-hydroxydopamine caused almost complete depletion of both adrenaline and noradrenaline from these organs of control and swimming-treated rats. Furthermore, a differential centrifugation study revealed that the microsomal fraction had the highest concentrations of both adrenaline and noradrenaline in the heart and spleen of control and stress-treated rats. These findings suggest that adrenaline, like noradrenaline, exists in sympathetic nerve endings in the peripheral organs of the rats under basal conditions, and the adrenaline contents in the nerve endings are increased under stress situations.