Acetylcholine-evoked currents in cultured neurones dissociated from rat parasympathetic cardiac ganglia

Lynne A Fieber, D. J. Adams

Research output: Contribution to journalArticle

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Abstract

The properties of acetylcholine (ACh)-activated ion channels of parasympathetic neurones from neonatal rat cardiac ganglia grown in tissue culture were examined using patch clamp recording techniques. Membrane currents evoked by ACh were mimicked by nicotine, attenuated by neuronal bungarotoxin, and unaffected by atropine, suggesting that the ACh-induced currents are mediated by nicotinic receptor activation. The current-voltage (I-V) relationship for whole-cell ACh-evoked currents exhibited strong inward rectification and a reversal (zero current) potential of -3 mV (NaCl outside, CsCl inside). The rectification was not alleviated by changing the main permeant cation or by removal of divalent cations from the intracellular or extracellular solutions. Unitary ACh-activated currents exhibited a linear I-V relationship with slope conductances of 32 pS in cell-attached membrane patches and 38 pS in excised membrane patches with symmetrical CsCl solutions. Acetylcholine-induced currents were reversibly inhibited in a dose-dependent manner by the ganglionic antagonists, mecamylamine (K(d) = 37 nM) and hexamethonium (IC50 ~ 1 μM), as well as by the neuromuscular relaxant, d-tubocurarine (K(d) = 3 μM). Inhibition of ACh-evoked currents by hexamethonium could not be described by a simple blocking model for drug-receptor interaction. The amplitude of the ionic current through the open channel was dependent on the extracellular Na+ concentration. The direction of the shift in reversal potential upon replacement of NaCl by mannitol indicates that the neuronal nicotinic receptor channel is cation selective and the magnitude suggests a high cation to anion permeability ratio. The cation permeability (P(X)/P(Na)) followed the ionic selectivity sequence Cs+ (1.06) > Na+ (1.0) > Ca2+ (0.93). Anion substitution experiments showed a relative anion permeability, P(Cl)/P(Na) ≤ 0.05. The nicotinic ACh-activated channels described mediate the responses of postganglionic parasympathetic neurones of the mammalian heart to vagal stimulation.

Original languageEnglish
Pages (from-to)215-237
Number of pages23
JournalJournal of Physiology
Volume434
StatePublished - Jan 1 1991

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Parasympathetic Ganglia
Acetylcholine
Neurons
Cations
Anions
Permeability
Hexamethonium
Nicotinic Receptors
Mecamylamine
Drug Receptors
Tubocurarine
Membranes
Divalent Cations
Mannitol
Patch-Clamp Techniques
Nicotine
Atropine
Drug Interactions
Ion Channels
Ganglia

ASJC Scopus subject areas

  • Physiology

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Acetylcholine-evoked currents in cultured neurones dissociated from rat parasympathetic cardiac ganglia. / Fieber, Lynne A; Adams, D. J.

In: Journal of Physiology, Vol. 434, 01.01.1991, p. 215-237.

Research output: Contribution to journalArticle

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