BODY-TEMPERATURE, MOTOR-ACTIVITY, AND FEEDING-BEHAVIOR OF MICE TREATED WITH BETA-CHLORNALTREXAMINE

The effects of an irreversible long term opioid antagonism on circadia n rhythms in body temperature (T-b), locomotor activity (Act) and feed ing under normal conditions and following lipopolysaccharide administr ation (LPS; 2.5 mg/kg) have been investigated in unrestrained mice hou sed at their thermoneutral zone (30 degrees C). beta-chlornaltrexamine (beta-CNA; 5 mg/kg) given intraperitoneally decreased T-b on the day of injection, depressed Act, and reduced food and water intake for sev eral days. The drug destroyed circadian rhythm in T-b for 4 consecutiv e days after administration due to prevention of the night time increa ses in temperature, whereas mean day time T-b of mice treated with bet a-CNA remained similar to controls. Between days 5-8 the day-time T-b of beta-CNA-injected mice decreased, and the mice started displaying r egular daily variations albeit with smaller amplitude and at lower lev el than controls. The depressive effect of beta-CNA on circadian varia tion in activity was more prolonged than its effect on T-b suggesting that these two variables are independently regulated. beta-CNA prevent ed the febrile response of the mice to LPS and enhanced the hypophagic effect of LPS. We conclude that normal circadian rhythms in T-b and A ct, as well as certain symptoms of sickness behavior, have an opioid c omponent.