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Direct muscarinic and nicotinic receptor‐mediated excitation of rat medial vestibular nucleus neurons in vitro
Author(s) -
Phelan Kevin D.,
Gallagher Joel P.
Publication year - 1992
Publication title -
synapse
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.809
H-Index - 106
eISSN - 1098-2396
pISSN - 0887-4476
DOI - 10.1002/syn.890100410
Subject(s) - muscarinic acetylcholine receptor , chemistry , depolarization , nicotinic antagonist , nicotinic agonist , neuroscience , mecamylamine , muscarine , bicuculline , muscarinic acetylcholine receptor m2 , postsynaptic potential , biophysics , receptor , biology , gabaa receptor , biochemistry
We have utilized intracellular recording techniques to investigate the cholinoceptivity of rat medial vestibular nucleus (MVN) neurons in a submerged brain slice preparation. Exogenous application of the mixed cholinergic agonists, acetylcholine (ACh) or carbachol (CCh), produced predominantly membrane depolarization, induction of action potential firing, and decreased input resistance. Application of the selective muscarinic receptor agonist muscarine (MUSC), or the selective nicotinic receptor agonists nicotine (NIC) or 1,1‐dimethyl‐4‐phenylpiperazinium (DMPP) also produced membrane depolarizations. The MUSC‐induced depolarization was accompanied by decreased conductance, while an increase in conductance appeared to underlie the NIC‐ and DMPP‐induced depolarizations. The muscarinic and nicotinic receptor mediated depolarizations persisted in tetrodotoxin and/or low Ca 2+ /high Mg 2+ containing media, suggesting direct postsynaptic receptor activation. The MUSC‐induced depolarization could be reversibly blocked by the selective muscarinic‐receptor antagonist, atropine, while the DMPP‐induced depolarization could be reversibly suppressed by the selective ganglionic nicotinicreceptor antagonist, mecamylamine. Some neurons exhibited a transient membrane hyperpolarization during the depolarizing response to CCh or MUSC application. This transient inhibition could be reversibly blocked by the γ‐aminobutyric acid (GABA) antagonist, bicuculline, suggesting that the underlying hyperpolarization results indirectly from the endogenous release of GABA acting at GABA receptors. This study confirms the cholinoceptivity of MVN neurons and establishes that individual MVN cells possess muscarinic as well as nicotinic receptors. The data provide support for a prominent role of cholinergic mechanisms in the direct and indirect regulation of the excitability of MVN neurons.