Muscarinic and β-adrenergic prejunctional modulation of adrenergic neurotransmission in the blood vessel wall

Abstract

Many prejunctional inhibitory and excitatory receptors have been described on adrenergic nerve endings in animal arteries and veins, and studies to date have identified some of these in human blood vessels. The latter include muscarinic receptors in cutaneous veins which when activated by acetylcholine inhibit the evoked release of norepinephrine, and β-adrenoceptors which when stimulated by isoproterenol or epinephrine facilitate it. Animal studies suggest that cholinergic vasodilatation can result from prejunctional inhibition of adrenergic neurotransmission. The human saphenous vein appears to contain more prejunctional β-adrenoceptors than the canine, with a consequential greater enhancement of norepinephrine release when these receptors are activated.