Behavioral and autonomic thermoregulation in the rat following chlordimeform administration

This study was designed to assess the effects of a single acute injection of chlordimeform (CDM) on some behavioral and autonomic effectors of the thermoregulatory system of the Sprague-Dawley rat. In one experiment rats injected intraperitoneally with 60 mg/kg CDM were placed in an environmental chamber set at an ambient temperature (Ta) of 5, 10, 15, 20, 25 or 30 degrees C for 60 min. Exposure to CDM resulted in hypothermia at Ta's of 5 to 25 degrees C and had no effect on body temperature at a Ta of 30 degrees C. In a second experiment, rats injected with 60 mg/kg CDM were placed in a temperature gradient which permitted the continuous recording of preferred Ta (i.e., behavioral thermoregulation), oxygen consumption (i.e., metabolic rate), and total activity. CDM-treated rats preferred Ta's of 20 degrees C after 60 min in the temperature gradient in spite of a hypothermic body temperature (35.3 degrees C). That is, the animals could have moved to the warm end of the gradient and thereby prevented a fall in body temperature. CDM also led to a significant reduction in oxygen consumption. In a third experiment, foot and tail skin temperature, and heart rate were recorded in anesthetized rats maintained under normothermia while treated with CDM. Tail and foot skin temperature rapidly increased following CDM administration which was indicative of peripheral vasodilation and increased heat loss. The changes in temperature were concomitant with an abrupt drop in heart rate.(ABSTRACT TRUNCATED AT 250 WORDS)