AUTONOMIC AND BEHAVIORAL THERMOREGULATION IN THE GOLDEN-HAMSTER DURING SUBCHRONIC ADMINISTRATION OF CLORGYLINE

Chronic administration of clorgyline, a type-A monoamine oxidase inhib itor, leads to a decrease in peritoneal (i.e., core) temperature of go lden hamsters. To better understand the mechanisms of clorgyline's the rmoregulatory effects, autonomic and behavioral thermoregulatory effec ters were measured in Syrian hamsters following chronic infusion of cl orgyline via a minipump (2 mg/kg/day). Metabolic rate, evaporative wat er loss, motor activity, and core temperature were measured after 60 m in of exposure to ambient temperatures (T-a) of 5, 20, 30, and 35 degr ees C. Behavioral thermoregulatory responses were assessed by measurin g 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 w ere significantly elevated in clorgyline-treated hamsters exposed to a T-a of 5 degrees C. There were no effects of clorgyline on evaporativ e water loss. In the temperature gradient the mean selected T-a of clo rgyline-treated hamsters was nearly equal to that of the saline-treate d hamsters, 30.7 and 31.2 degrees C, respectively. On the other hand, the mode of selected T-a in the clorgyline group was 2.8 degrees C hig her than that of the saline group. Motor activity in the gradient was significantly elevated and food consumption was depressed by clorgylin e treatment. Overall, these findings indicate that chronic clorgyline treatment in the golden hamster results in novel autonomic and behavio ral modification; it stimulates metabolic thermogenesis during cold ex posure, but appears to increase the behavioral zone of thermoneutralit y. This latter effect may mean an improvement in heat tolerance, sugge sting that this drug might assist in the adaptation to warm temperatur es.