Muscarinic receptor heterogeneity in guinea pig intestinal smooth muscle: binding studies with AF-DX 116.
Muscarinic receptor subtypes in longitudinal and circular smooth muscles of the guinea pig ileum were characterized with the use of the cardioselective antagonist AF-DX 116 in binding competition experiments against 0.3 nM [3H] N-methylscopolamine [( 3H]NMS). This compound recognized a heterogeneous receptor population in both smooth muscles, revealing the existence of different percentages of the cardiac (KD = 92-110 nM) and the glandular (KD = 1150-2541 nM) muscarinic receptor subtypes. These results, together with the low potency displayed by AF-DX 116 to inhibit the agonist-stimulated smooth muscle contraction and salivary secretion allow the suggestion that the glandular muscarinic receptor subtype, showing a low affinity for AF-DX 116, is involved in smooth muscle contraction.
Giraldo
E
E
Department of Biochemistry, Istituto De Angeli, Milan, Italy.
Monferini
E
E
Ladinsky
H
H
Hammer
R
R
D000818:Animals; D006168:Guinea Pigs; D066298:In Vitro Techniques; D008297:Male; D009130:Muscle, Smooth / Q000187:drug effects / Q000378:metabolism*; D009206:Myocardium / Q000378:metabolism; D010890:Pirenzepine / Q000031:analogs & derivatives* / Q000378:metabolism; D011976:Receptors, Muscarinic / Q000378:metabolism*; D012469:Salivary Glands / Q000378:metabolism
D011976:Receptors, Muscarinic; D010890:Pirenzepine; C048593:otenzepad