For this study, we compared the thermoregulatory involvement of noradrenaline (NA) in the medial preoptic area (mPOA) of non-cold acclimated rats to that of cold-acclimated rats. We quantified the release of NA in the mPOA during 3 h cold (5 °C) exposure in room-
temperature-acclimated rats (RA group, kept at 23 °C for 2 weeks) and cold-acclimated rats (CA group, kept at 5 °C for 2 weeks). We concurrently monitored the
core body temperature (
Tc), heart rate (HR), and tail skin
temperature (
Tt). Cold exposure significantly increased
Tc and HR, and decreased
Tt in both groups. However, the cold-induced increase of the extracellular NA levels in mPOA was observed only in the RA group: not in the CA group. To elucidate these different results in NA levels further, and to evaluate participation of the mPOA in thermoregulation in the cold, we measured
Tc, HR, and
Tt during perfusion of
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-adrenoceptor antagonist phenoxybenzamine during cold exposure (5 °C). This pharmacological procedure induced marked hypothermia, with decreases in HR only in the RA group; no changes were observed in
Tc or any thermoregulatory parameter in the CA group. These results suggest that NA in the mPOA modulates
heat production in response to acute cold stress in the RA group. However, this thermoregulatory action of NA in the mPOA was attenuated in the CA group.