Analysis of regional variations in the affinities of muscarinic agonists in the rat brain

John Ellis, Wayne Hoss

Research output: Contribution to journalArticlepeer-review

30 Scopus citations


The brain stem of the rat has a higher affinity toward muscarinic agonists than does the forebrain. Receptor occupancy curves of both regions of the brain deviate from simple mass-action binding. The characteristics of the binding in each region are compatible with the existence of two non-interacting binding sites, and are not attributable to desensitization or to negatively cooperative binding within a small oligomer; however, the possibility of large oligomers remains to be excluded. The agonist binding data were analyzed by a linear transformation of Scatchard-like inhibition curves of the binding of the antagonist [3H]quinuclidinyl benzilate (QNB). Such analysis, based on a model of two subpopulations of receptors in each area, shows the subpopulations of the brain stem and the forebrain to be distinct. Brain stem: 44% of receptors possess high affinity with dissociation constant for carbachol,KH = 2.8 × 10-8M, dissociation constant of low-affinity receptor,KL = 2.3 × 10-6M; forebrain: 41% high affinity,KH = 2.1 × 10-7M, KL = 1.7 × 10-5M. The data suggest that whole brain contains at least three major muscarinic receptors, which can be distinguished on the basis of their affinities for agonists.

Original languageEnglish (US)
Pages (from-to)189-198
Number of pages10
JournalBrain research
Issue number1
StatePublished - Jul 7 1980

All Science Journal Classification (ASJC) codes

  • General Neuroscience
  • Molecular Biology
  • Clinical Neurology
  • Developmental Biology


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