Characterization of muscarinic receptor subtypes in human tissues

Life Sci. 1988;43(19):1507-15. doi: 10.1016/0024-3205(88)90398-0.


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.

MeSH terms

  • Brain / metabolism*
  • Cerebellum / metabolism
  • Heart Atria / metabolism
  • Heart Ventricles / metabolism
  • Humans
  • Kinetics
  • Myocardium / metabolism*
  • N-Methylscopolamine
  • Organ Specificity
  • Pirenzepine / metabolism*
  • Receptors, Muscarinic / metabolism*
  • Scopolamine Derivatives / metabolism*
  • Submandibular Gland / metabolism*


  • Receptors, Muscarinic
  • Scopolamine Derivatives
  • Pirenzepine
  • N-Methylscopolamine