title: Muscarinic m3 receptors and dynamics of intracellular Ca2+ cerebellar granule neurons.
abstract: Activation of muscarinic receptors with carbachol has no effect on intracellular Ca2+ concentration in cerebellar granule cell cultures. Only after elevating intracellular Ca2+ concentrations using either 40 mM KCl or activating glutamatergic receptors was carbachol able to increase intracellular Ca2+. The response lasted about 10 s, and the median increase in intracellular Ca2+ with either 100 microM or 300 microM carbachol was about 85 nM. Carbachol at 30 microM elicited an increase in intracellular calcium that was half maximal. After a 16 min or 32 min delay following cell depolarization, responses to carbachol were only found in about 20% of the cells studied and the median increase in intracellular Ca2+ was about 14 nM. (-)-Quinuclidinylxanthene-9-carboxylate hemioxalate (QNX) at 10 nM (a muscarinic m3 antagonist), but not methoctramine at 5 microM (a muscarinic m2 antagonist), attenuated the action of 100 microM carbachol. This carbachol-mediated response was elicited in the absence of extracellular Ca2+ and in the presence of 10 microM dantrolene, but was blocked by 1 microM thapsigargin. Lastly, treatments of cerebellar granule cell cultures with carbachol (100 microM) for up to 12 h results in a desensitization of the carbachol-mediated release of stored Ca2+. Thus, carbachol acts on muscarinic m3 receptors to induce the release of Ca2+ from IP3-sensitive Ca2+ stores that must be filled by a prior period of high intracellular Ca2+.
authors.affiliation: Fidia Georgetown Institute for the Neurosciences, Georgetown University School of Medicine, Washington, DC.
authors.forename: E B
authors.initials: EB
authors.lastname: Fohrman
authors.forename: G
authors.initials: G
authors.lastname: de Erausquin
authors.forename: E
authors.initials: E
authors.lastname: Costa
authors.forename: W J
authors.initials: WJ
authors.lastname: Wojcik
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002217:Carbachol / Q000494:pharmacology*; D002478:Cells, Cultured; D002531:Cerebellum / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D003620:Dantrolene / Q000494:pharmacology; D003959:Diamines / Q000494:pharmacology; D016257:Fura-2; D005971:Glutamates / Q000494:pharmacology; D018698:Glutamic Acid; D008856:Microscopy, Fluorescence; D009474:Neurons / Q000187:drug effects / Q000378:metabolism*; D010276:Parasympatholytics / Q000494:pharmacology; D011812:Quinuclidines / Q000494:pharmacology; D051381:Rats; D017470:Receptors, Glutamate / Q000378:metabolism; D011976:Receptors, Muscarinic / Q000187:drug effects / Q000378:metabolism*; D013729:Terpenes / Q000494:pharmacology; D019284:Thapsigargin; D014966:Xanthenes / Q000494:pharmacology
chemical_list: D003959:Diamines; D005971:Glutamates; D010276:Parasympatholytics; D011812:Quinuclidines; D017470:Receptors, Glutamate; D011976:Receptors, Muscarinic; D013729:Terpenes; D014966:Xanthenes; C067669:3-quinuclidinyl xanthene-9-carboxylate; D018698:Glutamic Acid; D019284:Thapsigargin; D002217:Carbachol; D003620:Dantrolene; C054938:methoctramine; D002118:Calcium; D016257:Fura-2