Thermogenic changes with chronic cold exposure in the naked mole-rat (Heterocephalus glaber)

The naked mole-rat (Heterocephalus glaber) lives communally in a thermally buffered underground habitat. Here, it relies primarily on ectothermic (behavioral) mechanisms to maintain body temperature (T(b)). Outside this milieu, it is unable to effectively regulate T(b) and T(b) tracks that of ambient temperature (T(a)). Although naked mole-rats, in their natural habitat have little need for cold-tolerance, we questioned whether or not thermogenic capacity would change with prolonged (>1 year) exposure to cooler conditions. We hypothesized that these rodents would not conform to common mammalian patterns and that non-shivering thermogenic (NST) capacity would be unchanged with chronic cold exposure. The capacity for NST was assessed following noradrenaline administration (0.8 mg/kg, s.c.) to lightly anesthetized (pentobarbital 6% m/v 40 mg/kg) animals and monitoring the concomitant changes in oxygen consumption and T(b). Results concur with the null hypothesis in that prolonged cold exposure did not elicit any increase in NST capacity (1.52+/-0.17 ml O(2)/g/h, cold-acclimated; 1.73+/-0.31 ml O(2)/g/h, control; P>0.05). Rapid heat loss across their uninsulated integument may necessitate continuous maximal stimulation of brown adipose tissue (BAT), and as such, prevent any further increase in thermogenic capacity following cold exposure.