Local temperature modulates alpha 1- and alpha 2-adrenergic vasoconstriction in men

Area of Science:

• Physiology
• Pharmacology
• Dermatology

Background:

• Previous studies in canine saphenous veins indicated temperature-dependent alpha-adrenergic receptor responses.
• Cutaneous vascular beds, like the human finger, may exhibit distinct thermal modulation of adrenergic signaling.

Purpose of the Study:

• To investigate the effects of local cooling and warming on alpha 1- and alpha 2-adrenergic vasoconstriction in the human finger.
• To determine if temperature modulates alpha-adrenergic receptor-mediated vascular tone in human cutaneous vasculature.

Main Methods:

• Healthy men underwent brachial artery infusions of phenylephrine (alpha 1 agonist) and clonidine (alpha 2 agonist) with and without yohimbine (alpha 2 antagonist).
• Finger blood flow was measured using venous occlusion plethysmography on cooled and uncooled fingers.
• Sympathetic tone was modulated by leg immersion in cold water.

Main Results:

• Cooling augmented alpha 2-adrenergic vasoconstriction (clonidine-induced) and suppressed alpha 1-adrenergic vasoconstriction (phenylephrine-induced).
• Warming produced opposite effects, augmenting alpha 1- and reducing alpha 2-adrenergic vasoconstriction.
• Yohimbine partially blocked the cooling-induced augmentation of alpha 2-adrenergic vasoconstriction.

Conclusions:

• Local temperature significantly modulates alpha-adrenergic receptor function in the human finger.
• Cooling enhances alpha 2-adrenergic vasoconstriction and inhibits alpha 1-adrenergic vasoconstriction in cutaneous vascular beds.
• Warming has opposing effects, highlighting temperature-dependent regulation of vascular tone via adrenergic mechanisms.