Reactivity of helical strips of carotid arteries from cold- and warm-acclimated rabbits: effects of adrenergic agents, angiotensin II, and KCI.

Increased quantities of catecholamines are found in the adrenals of animals exposed to cold and thus, many studies have focused on determining the effects of catecholamines on metabolism (calorigenesis) and thermoregulation (vasomotor control of superficial blood vessels) during severe cld stress. Many of those studies have shown that the vasoconstriction which occurs in rabbit ears subsequent to an infusion of norepinephrine is diminished in cold-acclimated animals. The present in vitro study investigates the effects of 3 adrenergic agents (phenylephrine, norepinephrine, epinephrine) and 2 non-adrenergic agents (angiotensin II and KC1) on vascular smooth muscle which is though not to participate in the thermoregulatory processes. The sensitivity of helical strips of carotid arteries from cold-acclimated (CA) rabbits to phenylephrine, norepinephrine and angiotensin was decreased from control level (WA), as was the maximum developed tension. Epinephrine showed no statistically relevant decrease in sensitivity, and KC1, showed changes in neither sensitivity nor maximal tension. Histological examination of cross-sections of carotid arteries did not reveal any decrease in wall thickness which might account for the decrease in sensitivity and maximal tension. It is suggested that arterial smooth muscle throughout the body is affected by prolonged cold exposure in its responses to a wide range of constrictor agents.