Plasma catecholamines in rats exposed to cold: effects of ganglionic and adrenoreceptor blockade.

Exposure to cold (4 degrees C) of catheterized rats acclimated to 20 degrees C resulted in a progressive increase in plasma noradrenaline (NA) concentrations which reached values consistently more than twice the basal ones (20 degrees C) by about 30 min. No further increase in plasma NA levels were detected when the cold exposure was continued for 24 h. Plasma adrenaline (A) and dopamine levels did not change at any time studied. Adrenalectomized rats exposed to cold exhibited percent rises in plasma NA similar to those in intact rats. An increase in plasma A levels concomitant with that of NA was observed following exposure to cold of rats in which either basal catecholamine release was impaired by chlorisondamine or the vasoconstrictor response was impeded by phentolamine. Propranolol did not modify the acute neurosympathetic response to cold. Exposure to cold (4 degrees C) for short periods of time combined with the measurement of plasma catecholamines is proposed as a useful and reproducible method for studying a pure neurosympathetic response in the rat.