The release of catechols from the adrenal medulla on activation of the sympathetic vasodilator nerves to the skeletal muscles in the cat by hypothalamic stimulation.

Abstract

Summary. The amount of catechols secreted from the adrenal glands concomitant with activation of the sympathetic vasodilator outflow by hypothalamic stimulation was studied in 14 cats. Blood samples from the left adrenal vein were collected during control and stimulation periods, and were tested (rat uterus and rat colon) after separating adrenaline and noradrenaline by paper chromatography. The mean values for the adrenaline output in the control samples and those taken during hypothalamic stimulation of the sympathetic vasodilator area were 0.06 and 0.32 μg/kg/min (increase 433 per cent). The corresponding figures for noradrenaline were 0.19 and 0.35 μg/kg/min (increase 84 per cent). As will be seen from these values the increase of catechol output consisted predominantly of adrenaline. The conclusion is drawn that in most experiments the amounts of adrenaline released were of such a low magnitude as to have only minor vascular effects, they may have been sufficient to produce metabolic effects. The findings are discussed in view of our hypothesis that activation of the vasodilator outflow under physiologic conditions is an integral part of emergency reactions.