1. In canine cutaneous veins, local moderate warming (37°-41°C) augments the responsiveness to postjunctional α1-adrenergic stimulation but depresses that to postjunctional α2-adrenergic activation. Moderate cooling (37°-24°C) has the opposite effect.
2. The effects of warming and cooling on α1-adrenergic responses are buffered by a large receptor reserve, allowing for the predominance of alterations in α2-adrenergic responsiveness.