The role of the sympathoadrenergic reaction in adaptation of the organism to the action of + 6 Gz acceleration.

In experiments on rats the symphathoadrenergic reactivity after a + 6 Gz acceleration was investigated. Hypergravitation produced as a rule a short initial bradycardia, followed by tachycardia. Hexamethonium (C6), a peripheric ganglion-blocking agent, produced bradycardia, diminution or vanishing of the initial bradycardic episode, and a decreased tachycardic reaction. No initial bradycardic response was observed ater atropine. Atropinized and C6-treated rats showed an increased heart frequency response. Centrifugation produced a decreased adrenal catecholamine content and a blood noradrenaline elevation. C6 importantly decreased both catecholamines content in blood. On this background the acceleration produced a slight increase of both blood catecholamines.