Effects of apomorphine on thermoregulatory responses of rats to different ambient temperatures

Abstract

Either systemic or central administration of apomorphine produced dose-related decreases in rectal temperature at ambient temperatures (T_a) of 8 and 22 °C in rats. At T_a = 8 °C, the hypothermia was brought about by a decrease in metabolic rate (M). At T_a = 22 °C, the hypothermia was due to an increase in mean skin temperature, an increase in respiratory evaporative heat loss (E_res) and a decrease in M. This increased mean skin temperature was due to increased tail and foot skin temperatures. However, at T_a = 29 °C, apomorphine produced increased rectal temperatures due to increased M and decreased E_res. Moreover, the apomorphine-induced hypothermia or hyperthermia was antagonized by either haloperidol or 6-hydroxydopamine, but not by 5,6-dihydroxytryptamine. The data indicate that apomorphine acts on dopamine neurons within brain, with both pre- and post-synaptic sites of action, to influence body temperature.