Dopamine involvement in thermoregulatory responses to heat in rats

The role of dopamine in thermoregulatory challenges was studied in rats exposed to thermoneutrality then to heat with pretreatment by SCH23390 (i.p., D1/D5 receptor antagonist), sulpiride (i.p., D2 receptor antagonist) or piribedil (i.p., D2/D3 receptor agonist). Heat exposure leads to a rise in rectal temperature followed by a steady plateau ending with a terminal increase. The duration of both heat exposure and the plateau increased largely after SCH23390 and rose slightly after sulpiride. Piribedil was ineffective on these parameters but lowered rectal temperature at thermoneutrality. It is suggested that the thermoregulatory failure observed in heat-exposed rats may implicate dopamine through D1/D5 and in a lesser extent through D2 receptors. The inefficacy of piribedil suggests that dysregulations in synaptic transmission may exist.