[Changes in muscular thermogenesis in cold adapted rats following beta-adrenoreceptor blockade]

The administration of beta-adrenergic blocking agent propranolol to cold adapted rats entailed some decrease of the total metabolic reaction and body temperature as well as an additive (compensatory) increase of electrical muscle activity. The compensatory effect was more obvious in postural-tonic groups of muscles (m. trapezius, m. masseter) and in deeper portions of muscles (m. tibialis ant., m. trapezius), mainly presented by the red fibers. An adaptive increase of non-shivering thermogenesis and temperature effect of muscular contraction seem to be mainly controlled by beta-adrenergic mechanisms.