Muscarinic effects on cellular functions in cultured human ciliary muscle cells

S. Matsumoto, Thomas Yorio, L. DeSantis, Iok-Hou Pang

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Abstract

Purpose. To characterize the pharmacology of the carbachol-induced changes of phospholipase C (PLC) activity and intracellular calcium concentration ([Ca2+](i)) in cultured human ciliary muscle cells. Methods. Changes in PLC activity of cultured human ciliary muscle cells were determined by production of inositol phosphates. Single-cell dynamic fluorescence ratio imaging was used to determine [Ca2+](i). Results. Carbachol, oxotremorine-M, aceclidine, and pilocarpine stimulated PLC with mean EC50s of 20, 8, 17, and 2 μM, respectively. The effect of carbachol on PLC was partially suppressed by extracellular Ca2+ depletion. This muscarinic effect was blocked by muscarinic antagonists, such as atropine (apparent pK(i) = 9.12, nonselective for muscarinic receptor subtypes), pirenzepine (pK(i) = 6.76, selective for the M1 receptor subtype), 4DAMP (pK(i) = 9.25, selective for the M1 and M3 subtypes), and fHHSiD (pK(i) = 7.77, selective for the M3 subtype). In [Ca2+](i) experiments, carbachol increased [Ca2+](i) transients in human ciliary muscle cells in a dose-dependent manner with a mean EC50 of 7 μM. 4DAMP was approximately 100 times more potent than pirenzepine in the inhibition of the carbachol-induced [Ca2+](i) increase. [Ca2+](i) oscillations were observed after carbachol stimulation and persisted after extracellular Ca2+ depletion. Conclusions. Muscarinic agonists activate PLC and increase [Ca2+](i) in cultured human ciliary muscle cells through an M3-like muscarinic receptor subtype.

Original languageEnglish
Pages (from-to)3732-3738
Number of pages7
JournalInvestigative Ophthalmology and Visual Science
Volume35
Issue number10
Publication statusPublished - 1 Jan 1994

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Keywords

  • human ciliary muscle cell
  • intracellular calcium
  • M- muscarinic receptor subtype
  • muscarinic agonist
  • phospholipase C

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