![]() |
|
|
SV Jones, JL Barker, NJ Buckley, TI Bonner, RM Collins and MR Brann
Laboratory of Neurophysiology, National Institute of Neurological and Communicative Disorders and Stroke, Bethesda, Maryland 20892.
The electrophysiological responses to cholinergic stimulation of four cloned muscarinic receptor subtypes (m1-m4) were studied in A9 L cells transfected with the expression plasmids of each of the different subtypes, using the tight-seal whole-cell recording technique. Cells transfected with m1 and m3 muscarinic receptor subtypes were hyperpolarized by acetylcholine (ACh), whereas m2- and m4-transfected cells did not respond to ACh concentrations of up to 1 mM. Stimulation of both m1 and m3 muscarinic receptor subtypes evoked outward currents in cells voltage-clamped at -50 mV, associated with an increase in membrane conductance. These outward currents were blocked by atropine but not by tubocurarine. The ACh-induced currents of m1- and m3- transfected cells primarily involved potassium ions, although chloride ions also contributed to a minor extent. The potassium and chloride conductances were blocked by barium or cobalt and by buffering the intracellular calcium to low levels with 5 mM 1,2-bis(2- aminophenoxy)ethane-N,N,N'N'-tetraacetic acid, showing a dependence of these conductances on calcium. Thus, m1- and m3-transfected cells respond to ACh in a manner that is qualitatively similar, evoking calcium-dependent potassium and chloride conductances, whereas m2- and m4-transfected cells are not coupled to electrically detectable responses in A9 L cells.
This article has been cited by other articles:
![]() |
D. J. Ford, A. Essex, T. A. Spalding, E. S. Burstein, and J. Ellis Homologous Mutations Near the Junction of the Sixth Transmembrane Domain and the Third Extracellular Loop Lead to Constitutive Activity and Enhanced Agonist Affinity at all Muscarinic Receptor Subtypes J. Pharmacol. Exp. Ther., March 1, 2002; 300(3): 810 - 817. [Abstract] [Full Text] [PDF] |
||||
![]() |
C. Fromm, O. A. Coso, S. Montaner, N. Xu, and J. S. Gutkind The small GTP-binding protein Rho links G protein-coupled receptors and Galpha 12 to the serum response element and to cellular transformation PNAS, September 16, 1997; 94(19): 10098 - 10103. [Abstract] [Full Text] [PDF] |
||||
![]() |
J. Rousell, E.-B. Haddad, J. C. W. Mak, and P. J. Barnes Transcriptional Down-regulation of m2 Muscarinic Receptor Gene Expression in Human Embryonic Lung (HEL 299) Cells by Protein Kinase C J. Biol. Chem., March 31, 1995; 270(13): 7213 - 7218. [Abstract] [Full Text] [PDF] |
||||