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 thermogenesis in Syrian hamsters was investigated. The hamsters were cold-acclimated to 6 degrees C and their thermogenic response was investigated in an open-circuit system at 24 degrees C. Both norepinephrine and the beta(3)-specific adrenergic agonist CGP-12177 induced a high rate of nonshivering thermogenesis. However, neither CGP-12177 nor other beta(3)-selective agonists (BRL-37344, ICI-D7114) could induce nonshivering thermogenesis fully to the extent induced by norepinephrine. It was further observed that an apparent ''thermogenic refractoriness'' was induced by certain adrenergic agents (isoprenaline, CGP-12177) but not by others (norepinephrine, BRL-37344, ICID-7114). It is discussed whether the refractoriness could be secondary to effects of these agents on the vascular system. It is pointed out that the thermogenic response to adrenergic stimulation observed in the intact animal does not always fully correspond to what would be predicted from corresponding studies with isolated brown-fat cells.