STIMULATION OF NONSHIVERING THERMOGENESIS IN THE SYRIAN-HAMSTER BY NOREPINEPHRINE AND BETA-SELECTIVE ADRENERGIC AGENTS - A PHENOMENON OF REFRACTORINESS

The ability of different adrenergic agents to stimulate nonshivering t hermogenesis in Syrian hamsters was investigated. The hamsters were co ld-acclimated to 6 degrees C and their thermogenic response was invest igated in an open-circuit system at 24 degrees C. Both norepinephrine and the beta(3)-specific adrenergic agonist CGP-12177 induced a high r ate of nonshivering thermogenesis. However, neither CGP-12177 nor othe r beta(3)-selective agonists (BRL-37344, ICI-D7114) could induce nonsh ivering thermogenesis fully to the extent induced by norepinephrine. I t was further observed that an apparent ''thermogenic refractoriness'' was induced by certain adrenergic agents (isoprenaline, CGP-12177) bu t not by others (norepinephrine, BRL-37344, ICID-7114). It is discusse d whether the refractoriness could be secondary to effects of these ag ents on the vascular system. It is pointed out that the thermogenic re sponse to adrenergic stimulation observed in the intact animal does no t always fully correspond to what would be predicted from correspondin g studies with isolated brown-fat cells.