PT  - JOURNAL ARTICLE
AU  - Jones, S V
AU  - Barker, J L
AU  - Buckley, N J
AU  - Bonner, T I
AU  - Collins, R M
AU  - Brann, M R
TI  - Cloned muscarinic receptor subtypes expressed in A9 L cells differ in their coupling to electrical responses.
DP  - 1988 Oct 01
TA  - Molecular Pharmacology
PG  - 421--426
VI  - 34
IP  - 4
4099  - http://molpharm.aspetjournals.org/content/34/4/421.short
4100  - http://molpharm.aspetjournals.org/content/34/4/421.full
SO  - Mol Pharmacol1988 Oct 01; 34
AB  - 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.