NORADRENALINE INDUCES NONSHIVERING THERMOGENESIS IN BOTH THE NAKED MOLE-RAT (HETEROCEPHALUS-GLABER) AND THE DAMARA MOLE-RAT (CRYPTOMYS DAMARENSIS) DESPITE VERY DIFFERENT MODES OF THERMOREGULATION

1. An important component of endothermy in small mammals is achieved by the employment of nonshivering thermogenesis (NST). 2. Nonshivering thermogenic abilities of two subterranean mammals, the Damara mole-rat (Cryptomys damarensis) and the naked mole-rat (Heterocephalus glaber), were assessed by administering noradrenaline (0.8 mg/kg) to anaesthetized animals. These two species show very different modes of thermoregulation in that the former regulates body temperature whereas in the latter species body temperature closely tracks ambient temperature. 3. Both species showed the characteristic NST response by significantly increasing metabolic rate (C. damarensis), 194 +/- 57%; H. glaber, 356 +/- 199%) and body temperature (C. damarensis, 4.1 +/- 0.5 degrees C; H. glaber, 2.8 +/- 0.9 degrees C) with noradrenaline intervention. 4. These animals can therefore employ endothermy. While the Damara mole-rat conforms to mammalian thermoregulatory dogma and is homeothermic, the naked mole-rat may by definition be an 'endothermic poikilotherm'.