The thermal responses of three groups of control, 6-hydroxydopamine (6-OHDA) treated and 5,7-dihydroxytryptamine (5,7-DHT) treated rabbits to the administration of chlorpromazine (CPZ) were assessed at three different ambient temperatures (Ta: 2, 22, and 32 °C). Depleting catecholamines (CA) in brain with 6-OHDA produced a decrease in metabolic rate, in respiratory evaporative heat loss, and in ear blood flow at both Ta's of 2 and 22 °C, while depleting 5-hydroxytryptamine (5-HT) contents in brain with 5,7-DHT produced the opposite responses at the same Ta's. However, these amine-depleted animals maintained their rectal temperatures within normal limits over a wide range of Ta's tested. Furthermore, intraperitoneal administration of CPZ produced hypothermia at both Ta's of 2 and 22 °C. The major cause of the CPZ-induced hypothermia was an inhibition of metabolic heat production at Ta of 2 °C. At Ta of 22 °C, the CPZ-induced hypothermia was due to both a decrease in heat production and an increase in ear blood flow. However, CPZ hypothermia was attenuated in the CA-depleted animals, but was potentiated in the 5-HT-depleted animals. The data indicate that brain monoamines are involved in the central mechanisms of CPZ-induced hypothermia.
Monoamine Depletion by Reuptake Inhibitors [Expression of Concern]