Characteristics of body temperature, vasopressin, and oxytocin responses to endotoxin in the rat

Abstract

Several physiological variables were measured after endotoxin administration in the rat to examine the relationship between these variables. Rats responded to endotoxin with a biphasic body temperature response, an initial decrease and a subsequent increase in body temperature. Plasma vasopressin and oxytocin levels increased markedly after endotoxin administration. Diarrhea occurred in some animals. There was a strong negative correlation between increase in body temperature and base-line body temperature, and weak correlations between body weight and plasma vasopressin release and between base-line body temperature and minimum body temperature reached. Plasma vasopressin and oxytocin levels were correlated if samples from all time points were analyzed together, whereas they were not correlated if data from each time point were analyzed separately or if total peptide release for each rat was evaluated. These data suggest similar regulation for the release of vasopressin and oxytocin, that is, release by a common stimulus, but the magnitude of release of vasopressin and oxytocin appears to be independent, probably reflecting differences in synthesis and storage of these two peptides.