Electrical Activity of Skeletal Muscle of Normal and Acclimatized Rats on Exposure to Cold

Abstract

O2 consumption, body temp. and electrical activity of skeletal muscle of the rat were recorded simultaneously. At room temp. the electrical activity of the muscles of rats acclimatized to cold was less than that of non-acclimatized controls. In cold air (2-10[degree]C) electrical activity of the muscles increased before shivering was visible. The increase in electrical activity was greater in the non-acclimatized than in the acclimatized rats. At 30[degree]C the O2 consumption of the acclimatized rat was considerably higher than that of the non-acclimatized control; while at 2[degree]C the O2 consumption of acclimatized animals was of the same order, but still slightly higher, as in non-acclimatized rats (during the period in which body temp. was maintained). Anesthesia (urethane) while affecting the degree of muscle activity, did not affect the type of response observed. The increased rate of metabolism of visceral tissues plays an important part in the continued elevation of heat production in the acclimatized rat, and increased muscular activity is a "second line of defence" in the maintenance of body temp.