α2-Adrenergic receptors on the circular smooth muscle of canine small intestine Academic Article uri icon

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abstract

  • We have studied the distribution and properties of α2-adrenergic receptors in the circular muscle layer (containing deep muscular plexus) of canine small intestine. Using radioactively labelled rauwolscine, we located the binding sites to the neuronal membranes supporting the prejunctional action of α2-adrenergic agents in the gut. Moreover, although the functional data to suggest the existence of postjunctional α2-adrenergic receptors coupled to contraction are not available so far, we measured a substantial number of rauwolscine binding sites on the smooth muscle plasma membranes. Scatchard and Hill analyses of the saturation data were indicative of the presence of a single high affinity site (Hill coefficient 0.996) with a KD value of 8.8 nM and the maximum number of binding sites (Bmax) of 313 fmol/mg of protein. Competition studies suggested the presence of multiple subtypes of α2-adrenoceptors.Key words: [3H]rauwolscine, prejunctional, postjunctional, smooth muscle, enteric neurons.

publication date

  • June 1, 1991