Comparison of effect of environmental and preoptic cooling on plasma cortisol levels

Abstract

The acute exposure of dogs to an environmental temperature of 0 C evoked an elevation in plasma cortisol concentration which was apparent within 15 min and persisted for the 45 min of exposure. Gradual cooling of the environment over a 45-min period to a minimal temperature of 0 C failed to elevate plasma cortisol concentrations, although other compensatory mechanisms such as cutaneous vasoconstriction were active. Acute lowering of preoptic temperature also evoked a rise in plasma cortisol concentrations associated with lowering of pinna and elevation of rectal temperature. In this case the response was transient; plasma cortisol levels began to fall after 15 min of cooling even though cutaneous vasoconstriction was maintained. The results are interpreted to mean that acute lowering of environmental or preoptic temperature can activate the pituitary-adrenal system.