REACTIVITY OF HELICAL STRIPS OF CAROTID ARTERIES FROM COLD-ACCLIMATED AND WARM-ACCLIMATED RABBITS - EFFECTS OF ADRENERGIC AGENTS, ANGIOTENSIN-II, AND KCL

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  • 1 January 1981
    • journal article
    • research article
    • Vol. 253  (1) , 68-79
Abstract
Increased quantities of catecholamines are found in the adrenals of animals exposed to cold and many studies have focused on determining the effects of catecholamines on metabolism (calorigenesis) and thermoregulation (vasomotor control of superficial blood vessels) during severe cold stress. Many of those studies showed 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 KCl) on vascular smooth muscle which is thought not to participate in 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 KCl 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. Apparently, arterial smooth muscle throughout the body is affected by prolonged cold exposure in its responses to a wide range of constrictor agents.