The effect of experimental frost-bite on the responses of the rabbit ear-artery to adrenergic and electrical stimulation.

The aim of the present investigation was to study the effect of sub-zero temperatures on the adrenergic activated, smooth muscle-contraction of a peripheral blood-vessel. The central ear-artery of the rabbit was used for this purpose. The artery was stimulated to contract in vitro by activation of phentolamine sensitive, post-junctional, alpha-adrenoceptors by use of noradrenaline, or by noradrenaline released from noradrenergic nerves in the blood-vessel following electrical field stimulation. The effect of freezing the tissue in vivo for 15 min at sub-zero temperatures (-4, -6 and -9 degrees C) was studied in vitro. Exposure to -4 and -6 degrees C did not alter the apparent affinity (ED50) of noradrenaline significantly, when measured immediately, or 2 or 6 days after exposure. The maximal response to noradrenaline was reduced by approximately 54, 74 and 100% following exposure to -4, -6 and -9 degrees C, respectively. The response was completely restored after 2 and 6 days of regeneration in vivo following exposure to -6 degrees C, whereas the response after exposure to -9 degrees C was restored by only about 8 and 30% after 2 and 6 days regeneration, respectively. The maximal response to electrical field stimulation, which was completely inhibited by tetrodotoxin and phentolamine, was reduced by approximately 92% after exposure for 15 min to -4 and -6 degrees C, while it was completely inhibited after exposure to -9 degrees C. The response was restored by only 15-20% following 2 and 6 days in vivo after exposure to -6 degrees C.(ABSTRACT TRUNCATED AT 250 WORDS)