Muscarinic receptor-mediated excitation of rat intracardiac ganglion neurons.

Abstract

Modulation of the membrane excitability of rat parasympathetic intracardiac ganglion neurons by muscarinic receptors was studied using an amphotericin B-perforated patch-clamp recording configuration. Activation of muscarinic receptors by oxotremorine-M (OxoM) depolarized the membrane, accompanied by repetitive action potentials. OxoM evoked inward currents under voltage-clamp conditions at a holding potential of -60 mV. Removal of extracellular Ca(2+) markedly increased the OxoM-induced current (IOxoM). The inward IOxoM in the absence of extracellular Ca(2+) was fully inhibited by removal of extracellular Na(+), indicating the involvement of non-selective cation channels. The IOxoM was inhibited by organic cation channel antagonists including SKF-96365 and ML-204. The IOxoM was antagonized by muscarinic receptor antagonists with the following potency: 4-DAMP > pirenzepine = darifenacin > methoctramine. Muscarinic toxin 7 (MT-7), a highly selective inhibitor for M1 receptor, produced partial inhibition of the IOxoM. In the presence of MT-7, concentration-inhibition curve of the M3-preferring antagonist darifenacin was shifted to the left. These results suggest the contribution of M1 and M3 receptors to the OxoM response. The IOxoM was inhibited by U-73122, a phospholipase C inhibitor. The membrane-permeable IP3 receptor blocker xestospongin C also inhibited the IOxoM. Furthermore, pretreatment with thapsigargin and BAPTA-AM inhibited the IOxoM, while KN-62, a blocker of Ca(2+)/calmodulin-dependent protein kinase II, had no effect. These results suggest that the activation mechanism involves a PLC pathway, release of Ca(2+) from intracellular Ca(2+) stores and calmodulin. The cation channels activated by muscarinic receptors may play an important role in neuronal membrane depolarization in rat intracardiac ganglion neurons.

• Authors: Michiko Hirayama, Masanori Ogata, Tomoyuki Kawamata, Hitoshi Ishibashi
• Journal: Neuropharmacology (Neuropharmacology) Vol. 95 Pg. 395-404 (Aug 2015) ISSN: 1873-7064 [Electronic] England
• PMID: 25937214 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
• Copyright: Copyright © 2015 Elsevier Ltd. All rights reserved.

Chemical References

• Calmodulin
• Muscarinic Agonists
• Receptor, Muscarinic M1
• Receptor, Muscarinic M3
• Oxotremorine
• oxotremorine M
• Sodium
• Calcium-Calmodulin-Dependent Protein Kinase Type 2
• Type C Phospholipases
• Calcium

Topics

• Animals
• Calcium (metabolism)
• Calcium-Calmodulin-Dependent Protein Kinase Type 2 (antagonists & inhibitors, metabolism)
• Calmodulin (metabolism)
• Cells, Cultured
• Ganglia, Parasympathetic (drug effects, physiology)
• Membrane Potentials (drug effects, physiology)
• Muscarinic Agonists (pharmacology)
• Neurons (drug effects, physiology)
• Oxotremorine (analogs & derivatives, pharmacology)
• Patch-Clamp Techniques
• Rats, Wistar
• Receptor, Muscarinic M1 (agonists, metabolism)
• Receptor, Muscarinic M3 (agonists, metabolism)
• Sodium (metabolism)
• Type C Phospholipases (antagonists & inhibitors, metabolism)