Autonomic and behavioral thermoregulation in the golden hamster during subchronic administration of clorgyline

Abstract

Chronic administration of glorgyline, a type-A monoamine oxidase inhibitor, leads to a decrease inperitoneal (i.e., core) temperature of golden hamsters. To better understand the mechanisms of clorgyline's thermoregulatory effects, autonomic and behavioral thermoregulatory effectors were measured in Syrian hamsters following chronic infusion of clorgyline via a minipump (2 mg/kg/day). Metabolic rate, evaporative water loss, motor activity, and core temperature were measured after 60 min of exposure to ambient temperatures ( T a) of 5, 20, 30, and 35°C. Behavioral thermoregulatory responses were assessed by measuring selected T a and motor activity of the same animals in a temperature gradient over the course of 23 h. Metabolic rate and motor activity were significantly elevated in clorgyline-treated hamsters exposed to a T a of 5°C. There were no effects of clorgyline on evaporative water loss. In the temperature gradient the mean selected T a of clorgyline-treated hamsters was nearly equal to that of the saline-treated hamsters, 30.7 and 31.2°C, respectively. On the other hand, the mode of selected T a in the clorgyline group was 2.8°C higher than that of the saline group. Motor activity in the gradient was significantly elevated and food consumption was depressed by clorgyline treatment. Overall, these findings indicated the chronic clorgyline treatment in the golden hamsters results in novel autonomic and behavioral modification; it stimulates metabolic thermogenesis during cold exposure, but appears to increase the behavioral zone of thermoneutrality. This latter effect may mean an improvement in heat tolerance, suggesting that this drug might assist in the adaptation to warm temperatures.