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

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Abstract
Either systemic or central administration of apomorphine produced dose-related decreases in rectal temperature at ambient temperatures (Ta) of 8 and 22 °C in rats. At Ta = 8 °C, the hypothermia was brought about by a decrease in metabolic rate (M). At Ta = 22 °C, the hypothermia was due to an increase in mean skin temperature, an increase in respiratory evaporative heat loss (Eres) and a decrease in M. This increased mean skin temperature was due to increased tail and foot skin temperatures. However, at Ta = 29 °C, apomorphine produced increased rectal temperatures due to increased M and decreased Eres. 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.