Effects of Immobilization Stress on Renal Sympathetic Neurotransmission

Abstract

The effects immobilization stress on renal sympathetic neurotransmission as well as on heart, spleen and adrenal catecholamine content were examined in the rat. A single 2.5 hr stress period produced significant increases in blood pressure, heart rate, plasma norepinephrine and plasma epinephrine concentrations. However, no changes in renal catecholamine content or in stimulus-induced (1 Hz, 120 pulses, supramax. V) overflow of catecholamines were observed when the isolated perfused rat kidney was studied immediately after the 2.5 hr stress period. In contrast, the single stress period produced a 3-4 fold increase in cardiac epinephrine content while no effects on spleen or adrenal catecholamine content were observed. When stress was applied for 7 daily 2.5 hr periods, the repetition of the stress failed to produce any changes in renal neurotransmitter content or stimulus-induced overflow from the isolated perfused rat kidney. The data suggest that the accumulation of epinephrine into peripheral sympathetic nerves as a result of stress-induced adrenal catecholamine release is not a phenomenon which can be generalized to all regions of the cardiovascular system.