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Pharmacological characterization of native ?7 nicotinic ACh receptors and their contribution to depolarization-elicited exocytosis in human chromaffin cells.
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ABSTRACT: Background and purpose
Expression of ?7 nicotinic acetylcholine receptors (nAChRs) and their role in exocytosis have not yet been examined in human chromaffin cells.Experimental approach
To characterize these receptors and investigate their function, patch-clamp experiments were performed in human chromaffin cells from organ donors.Key results
The nicotinic current provoked by 300µM ACh in voltage-clamped cells was blocked by the nicotinic receptor antagonists ?-bungarotoxin (?-Bgtx; 1µM; 6 ± 1.7%) or methyllycaconitine (MLA; 10nM; 7 ± 1.6%), respectively, in an irreversible and reversible manner, without affecting exocytosis. Choline (10mM) pulses induced a biphasic current with an initial quickly activated (5.5 ± 0.4ms rise time) and inactivated component (8.5 ± 0.4ms time constant) (termed ?7), which was blocked by ?-Bgtx or MLA, followed by a slower component (non-?7). ?7 nAChR currents were dissected by blocking the non-?7 nAChR current component of the ACh and choline response with the ?6* nAChR blocker ?-conotoxin (?-Ctx) MII[S4A, E11A, L15A]. PNU-282987, an ?7 nAChR-specific agonist, elicited rapidly activated and rapidly inactivated currents. ?7 nAChR-positive allosteric modulators, such as 5-hydroxyindole (1mM) and PNU-120596 (10µM), potentiated responses that were blocked by ?-Bgtx or MLA. Exocytosis was evoked by depolarization-elicited ?7 nAChR currents, using choline in the presence of ?-Ctx MII[MS4A, E11A, L15A] or PNU-282987 as agonists.Conclusions and implications
Our electrophysiological recordings of pure ?7 nAChR currents elicited by rapid application of agonists demonstrated that functional ?7 nAChRs are expressed and contribute to depolarization-elicited exocytosis in human chromaffin cells.
SUBMITTER: Perez-Alvarez A
PROVIDER: S-EPMC3312488 | biostudies-literature | 2012 Feb
REPOSITORIES: biostudies-literature
Publications
Pharmacological characterization of native α7 nicotinic ACh receptors and their contribution to depolarization-elicited exocytosis in human chromaffin cells.
British journal of pharmacology 20120201 4
<h4>Background and purpose</h4>Expression of α7 nicotinic acetylcholine receptors (nAChRs) and their role in exocytosis have not yet been examined in human chromaffin cells.<h4>Experimental approach</h4>To characterize these receptors and investigate their function, patch-clamp experiments were performed in human chromaffin cells from organ donors.<h4>Key results</h4>The nicotinic current provoked by 300µM ACh in voltage-clamped cells was blocked by the nicotinic receptor antagonists α-bungaroto ...[more]