Modulation of postjunctional alpha-adrenergic responsiveness by local changes in temperature.

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