Experiments were designed to determine the effects of cooling on α1- and α2-adrenergic responses in isolated canine cutaneous veins. Rings of saphenous veins were suspended for isometric tension recording in physiological salt solution. Cooling (from 37 to 24°C) augmented contractions to norepinephrine under control conditions and after α1-adrenergic blockade (prazosin) but not following α2-adrenergic blockade (rauwolscine). Cooling augmented contractions evoked by the α2-adrenergic agonists B-HT 920 and UK 14304 but did not affect responses to the full α1-adrenergic agonist phenylephrine. These experiments suggest that cooling augments α2-adrenergic responsiveness without affecting α1-adrenergic responsiveness. However, the contractions evoked by the partial α1-adrenergic agonist St 587 were virtually abolished by cooling. Moreover, following partial irreversible blockade of the α1-adrenoceptors with phenoxybenzamine, cooling also reduced the contractions evoked by phenylephrine. Therefore, cooling reduces α1-adrenergic responsiveness in canine cutaneous veins, but in the case of full α1-adrenergic agonists such as norepinephrine and phenylephrine the inhibitory effect of cooling is buffered by an α1-adrenoceptor reserve. With norepinephrine, this permits the potentiating effect of cooling on the α2-adrenergic component of the response to predominate.
|Original language||English (US)|
|Journal||American Journal of Physiology - Heart and Circulatory Physiology|
|Publication status||Published - 1985|
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