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

Abstract

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.