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Activation of neurokinin 3 receptor increases Na v 1.9 current in enteric neurons
Author(s) -
Copel Carine,
Osorio Nancy,
Crest Marcel,
Gola Maurice,
Delmas Patrick,
Clerc Nadine
Publication year - 2009
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.2009.169409
Subject(s) - patch clamp , endocrinology , agonist , medicine , chemistry , desensitization (medicine) , biophysics , protein kinase c , myenteric plexus , tetrodotoxin , receptor , enteric nervous system , biology , signal transduction , biochemistry , immunohistochemistry
The intrinsic primary afferent neurons (IPANs) of the guinea pig enteric nervous system express Na v 1.9 sodium channels that produce a persistent TTX‐resistant current having a low activation threshold and slow gating kinetics. These neurons receive slow EPSPs induced mainly by the activation of neurokinin 3 receptors (NK3r). Here, we demonstrate that senktide, a specific NK3r agonist, potentiates the Na v 1.9 current ( I Nav1.9 ) in IPANs. Using whole‐cell patch‐clamp recordings from IPANs in duodenum longitudinal muscle/myenteric plexus preparations, we show that short (1–5 s) and long (up to 1 min) applications of senktide, increase the I Nav1.9 peak current up to 13‐fold. The effect, blocked by a NK3r antagonist SB235375 is transient, lasting ∼2 min and is due to a negative shift of the activation voltage by ∼20 mV and of fast inactivation by ∼10 mV. As a consequence, the window current resulting from the product of the activation and fast inactivation curves is shifted and enlarged. The transient effect of senktide is likely to be due to the fast desensitization of NK3r. Protein kinase C (PKC) activation with phorbol or oleoyl acetylglycerol also increases I Nav1.9 , although persistently, by inducing similar voltage‐dependent changes. Current‐clamp experiments showed that I Nav1.9 modulation by senktide lowers action potential threshold and increases excitability. The increase in I Nav1.9 by NK3r activation is also likely to amplify slow EPSPs generated in the IPANs. These changes in excitability potentially have a profound effect on the entire enteric synaptic circuit and ultimately on gut motility and secretion.