LOWERING OF BODY CORE TEMPERATURE BY EXPOSURE TO A COLD ENVIRONMENT AND BY A 5-HT(1A) AGONIST - EFFECTS OF PHYSIOLOGICAL AND PSYCHOLOGICAL VARIABLES AND BLOOD SEROTONIN LEVELS

The present study was designed to compare the effects of a pharmacolog ically induced decrease in body core temperature to the effects observ ed with lowering of body temperature by exposure to a cold environment . Our special interest was the involvement of 5-HT in thermoregulatory responses. Sixty healthy male volunteers were randomly assigned to on e of the following conditions: exposure to normal ambient temperature (28-degrees-C) and placebo, exposure to cold ambient temperature (5-de grees-C) and placebo, or normal ambient temperature and 10 mg of the p artial 5-HT1A agonist ipsapirone. As indicators of physiological respo nses to lowering of body temperature, tympanic temperature, skin tempe rature, EMA, metabolic rate, and heart rate were monitored and saliva cortisol levels and peripheral 5-HT concentrations were determined. In addition, ratings on ambient temperature, thermal discomfort, and fee lings of irritability were obtained. While lowering of body core tempe rature was associated with marked counterregulations (decrease of skin temperature, increase in EMA and metabolic rate) and feelings of disc omfort, this was not observed with ipsapirone. An increase in cortisol levels was primarily observed in the ipsapirone group and was not ref lected by respective changes in whole blood or platelet 5-HT indicatin g that brain and platelet 5-HT are not related.