Biogenic amines and thermoregulatory changes.

This review recapitulates the general principles of the organization of the thermoregulatory system, describes the thermoregulatory reactions of small and large mammals to hot environment and analyzes the probable roles of biogenic amines in these responses. Catecholamines found in peripheral blood plasma or excreted in urine represent a spillover of mediators released partly from sympathetic nerve endings and partly from the adrenal medulla. Since the thermoregulatory efforts differ between small and large mammals in cold and hot environments, the peripheral release of catecholamines is also different in these animals. The levels of these signal substances in the blood, as well as their peripheral metabolic and functional effects, serve as feedback signals for the hypothalamic integrative circuitry. The roles of antagonistic modulatory monoaminergic systems, ascending from the lower brain stem to the hypothalamus, in these integrations were discussed only partly, because this was a topic of another recent review (Zeisberger and Roth, 1996).