Evidence of 2-Adrenoceptors in the Nasal Blood Vessels of the Dog

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Abstract
• α-Adrenoceptor subtypes were demonstrated in an in vitro preparation of the vascular smooth muscle of the canine nasal mucosa. α1-Receptors were located on the surface of vascular smooth muscle (postsynaptic). α2 Subtypes were situated both at postsynaptic and presynaptic sites on adrenergic nerve terminals. Presynaptic α2-adrenoceptor stimulation yielded an inhibition of excessive norepinephrine release from nerve terminals. Stimulation of postsynaptic receptors, either α1 or α2, produced vasoconstriction. Although there was good evidence of the presence of postsynaptic α2-receptors, they did not appear to be dominant among the postsynaptic receptors. (Arch Otolaryngol 1984;110:647-651)