Abstract
Modulation of the standing outward current (I (SO)) by muscarinic acetylcholine (ACh) receptor (MAChR) stimulation is fundamental for the state-dependent change in activity mode of thalamocortical relay (TC) neurons. Here, we probe the contribution of MAChR subtypes, G proteins, phospholipase C (PLC), and two pore domain K(+) (K(2P)) channels to this signaling cascade. By the use of spadin and A293 as specific blockers, we identify TWIK-related K(+) (TREK)-1 channel as new targets and confirm TWIK-related acid-sensitve K(+) (TASK)-1 channels as known effectors of muscarinic signaling in TC neurons. These findings were confirmed using a high affinity blocker of TASK-3 and TREK-1, namely, tetrahexylammonium chloride. It was found that the effect of muscarinic stimulation was inhibited by M(1)AChR-(pirenzepine, MT-7) and M(3)AChR-specific (4-DAMP) antagonists, phosphoinositide-specific PLCβ (PI-PLC) inhibitors (U73122, ET-18-OCH(3)), but not the phosphatidylcholine-specific PLC (PC-PLC) blocker D609. By comparison, depleting guanosine-5'-triphosphate (GTP) in the intracellular milieu nearly completely abolished the effect of MAChR stimulation. The block of TASK and TREK channels was accompanied by a reduction of the muscarinic effect on I (SO). Current-clamp recordings revealed a membrane depolarization following MAChR stimulation, which was sufficient to switch TC neurons from burst to tonic firing under control conditions but not during block of M(1)AChR/M(3)AChR and in the absence of intracellular GTP. These findings point to a critical role of G proteins and PLC as well as TASK and TREK channels in the muscarinic modulation of thalamic activity modes.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Action Potentials / drug effects
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Action Potentials / physiology*
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Animals
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Cholinergic Neurons / drug effects
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Cholinergic Neurons / physiology*
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Electrophysiological Phenomena / drug effects
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Electrophysiological Phenomena / physiology
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GTP-Binding Protein alpha Subunits, Gq-G11 / genetics
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Gene Expression / genetics
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Guanosine Diphosphate / analogs & derivatives
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Guanosine Diphosphate / pharmacology
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Guanosine Triphosphate / antagonists & inhibitors
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Guanosine Triphosphate / metabolism
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Hydrogen-Ion Concentration
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Lateral Thalamic Nuclei / cytology
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Lateral Thalamic Nuclei / physiology
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Membrane Potentials / drug effects
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Membrane Potentials / physiology
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Muscarine / pharmacology
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Muscarinic Agonists / pharmacology
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Muscarinic Antagonists / pharmacology
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Nerve Tissue Proteins
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Oxotremorine / analogs & derivatives
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Oxotremorine / pharmacology
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Patch-Clamp Techniques
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Phospholipase C beta / antagonists & inhibitors
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Phospholipase C beta / genetics
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Phospholipase C beta / metabolism
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Potassium Channels, Tandem Pore Domain / antagonists & inhibitors
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Potassium Channels, Tandem Pore Domain / genetics
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Potassium Channels, Tandem Pore Domain / metabolism
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Rats
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Rats, Long-Evans
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Receptor, Muscarinic M1 / agonists
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Receptor, Muscarinic M1 / antagonists & inhibitors
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Receptor, Muscarinic M1 / genetics
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Receptor, Muscarinic M1 / metabolism
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Receptor, Muscarinic M3 / antagonists & inhibitors
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Receptor, Muscarinic M3 / genetics
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Receptor, Muscarinic M3 / metabolism
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Signal Transduction / drug effects
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Signal Transduction / physiology*
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Sleep / physiology*
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Thalamus / cytology
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Thalamus / physiology*
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Thionucleotides / pharmacology
Substances
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Kcnk9 protein, rat
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Muscarinic Agonists
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Muscarinic Antagonists
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Nerve Tissue Proteins
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Potassium Channels, Tandem Pore Domain
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Receptor, Muscarinic M1
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Receptor, Muscarinic M3
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Thionucleotides
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potassium channel protein TREK-1
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Guanosine Diphosphate
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potassium channel subfamily K member 3
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Oxotremorine
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oxotremorine M
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guanosine 5'-O-(2-thiodiphosphate)
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Muscarine
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Guanosine Triphosphate
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Phospholipase C beta
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GTP-Binding Protein alpha Subunits, Gq-G11