Effect of High Gz Forces on Sympathetic Nervous Activity.

摘要

Plasma epinephrine, norepinephrine and dopamine-beta-hydroxylase were used to quantitate the degree of sympathetic activation undergone by miniature swine and by men. Swine exposed to high Gz forces have massive output of norepinephrine which falls off rapidly during return to 1 G. Repeated exposures are characterized by a further increase of norepinephrine demonstrating large reserve stores and increased norepinephrine to prolonged stress. These animals also had a massive adrenomedullary output of epinephrine during the stress of high Gz and epinephrine output was even greater after repeated stresses. High Gz exposed swine increased circulating levels of dopamine-beta-hydroxylase and greatly increased levels after five exposures to high Gz. Dopamine-beta-hydroxylase levels, unlike those of norepinephrine and epinephrine, may provide a measure of sympathetic nervous stress that occurred minutes or hours in the past. Human subjects exposed to high Gz forces had basal norepinephrine levels and norepinephrine levels after the termination of high Gz similar to miniature swine. People who have severe head injuries have increased circulating norepinephrine and are subject to development of myocardial lesions. It is possible for men to develop cardiac lesions similar to those previously noted in the adult miniature swine, and these lesions may be caused by the release of endogenous catecholamines. Keywords: Response biology; Physiological effects; Acceleration tolerance; Stress physiology.(kt)