Wheel running behavior and thermoregulation in mice: effects of MDMA and methamphetamine

Abstract

MDMA and methamphetamine (METH) have profound effects on locomotor activity and thermoregulation in rodents. Similarly, spontaneous wheel running behavior increases core temperature in rodents. To study the interaction of these pharmacological and behavioral variables, rediotelemetry probes capable of measuring core temperature were surgically implanted into the peritoneal cavities of male Swiss Wesbter mice. Upon recovery, mice were housed in light‐ and sound‐attenuating chambers containing computer interface equipment for the radiotelemetry probes, a house light (lights off at 13:00 h and on at 01:00 h), a data logger to record ambient temperature, and an exhaust fan. Each mouse had access to ad lib food and water within its home cage, as well as a low profile running wheel, allowing simultaneous collection of wheel running behavior and core temperature across the circadian cycle. Under baseline conditions, ~95% of all wheel running behavior occurred during the subjective dark phase. During wheel running bouts, core temperature increased ~2.5°C, and was tightly correlated with wheel running activity. Injections of MDMA (5 and 10 mg/kg) and METH (1 and 5 mg/kg) were administered at 12:45 h, 15 m prior to the onset of the subjective dark phase and wheel running activity. The effects of these drugs on core temperature and wheel running behavior will be presented. These studies funded, in part, by NIH grant RR020146.