Desensitization of muscarinic M1 receptors of murine neuroblastoma cells (clone N1E-115) without receptor down-regulation and protein kinase C activity

Shigenobu Kanba, Kiyoko S. Kanba, Michael McKinney, Michael Pfenning, Robert Abraham, Soichiro Nomura, Lori Enloes, Scott Mackey, Elliott Richelson

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13 Citations (Scopus)


Acute desensitization of M1 muscarinic receptor-mediated responses (cyclic GMP formation and inositol phosphate release) was studied in murine neuroblastoma cells (N1E-115 clone). After a 45-min incubation at 37° of N1E-115 cells either in monolayer or in suspension, with the muscarinic agonist carbachol (1 mM), the receptor-mediated cyclic GMP response to carbachol was nearly completely lost. This loss was associated with > 80% loss of carbachol-mediated inositol phosphate release. The protein kinase C activator phorbol 12-myristate 13-acetate (PMA) inhibited both responses with similar potencies. Carbachol or PMA reduced by 30-40% the number of muscarinic receptor sites for antagonist and agonist on intact cells (determined in binding assays using [3H]N-methylscopolamine) only for cells in monolayer and not for those in suspension. PMA but not carbachol pretreatment of cells in monolayer or in suspension caused a translocation of [3H]phorbol 12,13-dibutyrate binding and protein kinase C activity. In addition, desensitization to carbachol occurred in cells largely depleted of protein kinase C by chronic exposure to PMA. Thus, agonist-mediated down-regulation is not needed for muscarinic M1 receptor desensitization, which may be a result of the activation of a receptor-activated kinase different from protein kinase C.

Original languageEnglish
Pages (from-to)1005-1014
Number of pages10
JournalBiochemical Pharmacology
Issue number5
Publication statusPublished - Sep 1 1990
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Biochemistry
  • Pharmacology


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