Thermoregulatory effects of intraventricularly injected dopamine in the goat

Dopamine (DA) was injected in the third brain ventricle of goats and the thermoregulatory effects were studied under different ambient conditions. The effects depended on dose, ambient conditions and cannula used. In the cold, there was a drop in body temperature, sometimes accompanied by suppression of shivering and by vasodilatation. Both temperature decrease and suppression of shivering were dose-dependent but there was no relation between magnitude of temperature drop and occurrence of shivering suppression. In a thermoneutral environment, there was either a slight vasoconstriction or hypothermia, occasionally accompanied by induction of panting. In the heat, either hypothermia or hyperthermia was observed. Hypothermia was accompanied by an increase in panting. Hyperthermia only occurred when the animals became excited as a result of the injection of DA. It is concluded that DA acts by stimulating the thermoregulatory pathway from heat sensors to heat loss effectors at a locus similar to that for 5-hydroxytryptamine in the thermoregulation model of Bligh et al. (1971).