Effects of adrenalectomy and chronic guanethidine treatment on tissue adrenaline concentrations in swimming-exposed rats.

Adrenaline is known to increase in extra-adrenal peripheral organs as well as urine and plasma in the rat after swimming stress. In order to clarify the physiological significance of adrenaline in stress responses, the origin and location of adrenaline in the peripheral organs were examined by measuring adrenaline in the heart, spleen, submaxillary gland and some other organs after adrenalectomy or guanethidine treatment. After bilateral adrenalectomy, adrenaline in the peripheral organs mostly disappeared. Swimming stress caused no increase in the adrenaline content of the organs in the adrenalectomized rats, while a marked increase was observed in the sham-operated animals. In guanethidine-treated rats, the adrenaline content of the peripheral organs was extremely low as compared to that in the saline-treated animals, and the swimming-induced increase in adrenaline level in the organs was greatly suppressed. These observations suggest that the organ adrenaline, which exists in sympathetic nerve endings, is mostly derived from the adrenal gland. It is considered that adrenaline would be involved in sympathetic neurotransmission, especially under stressful conditions.