Effect of stress on the uptake of 3H-norepinephrine into rat myocardium.

Spontaneously beating atria from rats previously exposed to irregular, signalled footshock were incubated with 3H-norepinephrine. A significant reduction in the uptake and retention of radioactivity was found in the atria from stressed animals compared with unstressed controls. A kinetic study of the uptake process in both the stressed and control groups showed a similar Km value but a significantly different Vmax. It was concluded that the enhanced myocardial sensitivity to catecholamines previously reported can be explained in part, on the basis of an inhibition of neuronal uptake.