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Functional role of cyclic nucleotide‐gated channels in rat medial vestibular nucleus neurons
Author(s) -
Podda Maria Vittoria,
D'Ascenzo Marcello,
Leone Lucia,
Piacentini Roberto,
Azzena Gian Battista,
Grassi Claudio
Publication year - 2008
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.2007.146019
Subject(s) - depolarization , cyclic nucleotide gated ion channel , medial vestibular nucleus , membrane potential , hyperpolarization (physics) , chemistry , biophysics , patch clamp , reversal potential , neuroscience , microbiology and biotechnology , cyclic nucleotide , vestibular nuclei , electrophysiology , biology , vestibular system , biochemistry , nucleotide , stereochemistry , nuclear magnetic resonance spectroscopy , gene
Although cyclic nucleotide‐gated (CNG) channels are expressed in numerous brain areas, little information is available on their functions in CNS neurons. The aim of the present study was to define the distribution of CNG channels in the rat medial vestibular nucleus (MVN) and their possible involvement in regulating MVN neuron (MVNn) excitability. The majority of MVNn expressed both CNG1 and CNG2 A subunits. In whole‐cell current‐clamp experiments carried out on brainstem slices containing the MVNn, the membrane‐permeant analogues of cyclic nucleotides, 8‐Br‐cGMP and 8‐Br‐cAMP (1 m m ), induced membrane depolarizations (8.9 ± 0.8 and 9.2 ± 1.0 mV, respectively) that were protein kinase independent. The cGMP‐induced depolarization was associated with a significant decrease in the membrane input resistance. The effects of cGMP on membrane potential were almost completely abolished by the CNG channel blockers, Cd 2+ and l ‐ cis ‐diltiazem, but they were unaffected by blockade of hyperpolarization‐activated cyclic nucleotide‐gated channels. In voltage‐clamp experiments, 8‐Br‐cGMP induced non‐inactivating inward currents (−22.2 ± 3.9 pA) with an estimated reversal potential near 0 mV, which were markedly inhibited by reduction of extracellular Na + and Ca 2+ concentrations. Membrane depolarization induced by CNG channel activation increased the firing rate of MVNn without changing the action potential shape. Collectively, these findings provide novel evidence that CNG channels affect membrane potential and excitability of MVNn. Such action should have a significant impact on the function of these neurons in sensory–motor integration processes. More generally, it might represent a broad mechanism for regulating the excitability of different CNS neurons.