Effects of depolarization and QX-314 injection on slow prepotentials in rat hippocampal pyramidal neurones in vitro.
A slow prepotential preceding the action potential elicited by 40-80 ms depolarizing current pulses injected in CA1 pyramidal cells in rat hippocampal slices was isolated and characterized using a subtraction procedure. The exponentially rising slow prepotential showed enhanced amplitude at depolarized membrane potential levels. In sufficient doses, intracellular injection of the lidocaine derivative QX-314 selectively blocked the slow prepotential, leaving the action potential largely unchanged. These results suggest that the slow prepotential might be mediated by a persistent sodium conductance or threshold channels recently found in various nerve cells, and could trigger action potentials in situations with a long-lasting depolarization.
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Institute of Neurophysiology, University of Oslo, Norway.
D000200:Action Potentials / Q000187:drug effects; D000779:Anesthetics, Local / Q000008:administration & dosage / Q000494:pharmacology*; D000818:Animals; D006624:Hippocampus / Q000187:drug effects* / Q000502:physiology; D008012:Lidocaine / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000494:pharmacology; D008297:Male; D008845:Microinjections; D009474:Neurons / Q000187:drug effects* / Q000502:physiology; D051381:Rats; D011919:Rats, Inbred Strains
D000779:Anesthetics, Local; C012647:QX-314; D008012:Lidocaine