Characterization of muscarinic receptor subtypes in human tissues |
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Authors: | E Giraldo F Martos A Gomez A Garcia M A Vigano H Ladinsky F Sanchez de La Cuesta |
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Institution: | Department of Biochemistry, Istituto De Angeli S.p.A., Milan, Italy. |
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Abstract: | The affinities of selective, pirenzepine and AF-DX 116, and classical, N-methylscopolamine and atropine, muscarinic cholinergic receptor antagonists were investigated in displacement binding experiments with 3H]Pirenzepine and 3H]N-methylscopolamine in membranes from human autoptic tissues (forebrain, cerebellum, atria, ventricle and submaxillary salivary glands). Affinity estimates of N-methylscopolamine and atropine indicated a non-selective profile. Pirenzepine showed differentiation between the M1 neuronal receptor of the forebrain and the receptors in other tissues while AF-DX 116 clearly discriminated between muscarinic receptors of heart and glands. The results in human tissues confirm the previously described selectivity profiles of pirenzepine and AF-DX 116 in rat tissues. These findings thus reveal the presence also in man of three distinct muscarinic receptor subtypes: the neuronal M1, the cardiac M2 and the glandular M3. |
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