Mechanisms underlying anoxic hyperpolarization of hippocampal neurons.
The outward current evoked in CA1 neurons by brief anoxia is strongly voltage dependent and is abolished by an atropine-sensitive action of carbachol (and also when recording with a GTP gamma S-containing microelectrode). In this respect, it closely resembles the M-type K current, but the involvement of other, voltage-independent, carbachol-sensitive K channels has not been excluded. When the anoxic outward current is eliminated, an anoxic inward current is revealed, which may be Cl- mediated. It is suggested that an early release of Ca2+ from a dantrolene (and perhaps GTP)-sensitive internal store activates Ca-sensitive Cl channels, as well as carbachol-sensitive (mainly M-type?) K channels. The opposing Cl- and K currents would account for the variable depolarizing and hyperpolarizing effects of anoxia.
Krnjević
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K
Anaesthesia Research Department, McGill University, Montréal, Qué.
Xu
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D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D002217:Carbachol / Q000494:pharmacology; D002712:Chlorides / Q000378:metabolism; D003620:Dantrolene / Q000494:pharmacology; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000494:pharmacology; D006624:Hippocampus / Q000378:metabolism*; D000860:Hypoxia / Q000378:metabolism*; D066298:In Vitro Techniques; D007473:Ion Channels / Q000187:drug effects / Q000378:metabolism*; D009474:Neurons / Q000378:metabolism*; D015221:Potassium Channels / Q000187:drug effects; D011712:Pyramidal Tracts / Q000166:cytology / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D011976:Receptors, Muscarinic / Q000187:drug effects
D002712:Chlorides; D007473:Ion Channels; D015221:Potassium Channels; D011976:Receptors, Muscarinic; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D002217:Carbachol; D003620:Dantrolene