Independent roles of dopamine D 1 and D 2/3 receptors in rat thermoregulation

Abstract

The present study was designed to examine a possible interaction between dopamine D 1 and D 2/3 receptors involved in thermoregulation in rats. The dose-dependent hypothermia produced by the dopamine D 1 receptor agonist A 68930 (0.9–15.0 μmol kg −1, s.c.), was augmented in an additive manner by pretreatment with the dopamine D 2/3 receptor agonist 7-OH-DPAT (0.06 μmol kg −1, s.c.). The dose-dependent hypothermia produced by 7-OH-DPAT (0.06–1.00 μmol kg −1 s.c.) was also augmented in an additive manner by pretreatment with A 68930 (0.9 μmol kg −1 s.c.). In contrast to these observations, locomotor activity measurements disclosed a marked interaction between the dopamine D 1 and D 2/3 receptor agonists. Thus, A 68930 (0.9–15.0 μmol kg −1, s.c.) produced a dose-dependent suppression of open-field locomotor activity. The addition of 7-OH-DPAT (1.00 μmol kg −1, s.c.), which by itself produced a weak suppression of locomotor activity, resulted in a gradual reversal of the A 68930-induced suppression of the locomotor activity. Thus, the present results provides strong support for an independent role of dopamine D 1 receptors in rat thermoregulatory mechanisms, distinct from effects mediated via the dopamine D 2 receptor family.