Intracellular effects of QX-314 and Cs+ in hippocampal pyramidal neurons in vivo.
The effects of intracellular diffusion of the lidocaine derivative anesthetic QX-314 and of Cs+, which block Na+ and K+ conductances, respectively, were investigated in vivo in rat CA1 and CA3 pyramidal neurons to demonstrate slow Ca(2+)-related events. QX-314 loading prevented fast Na+ spikes, but slower presumably Ca2+ spikes remained. A slower and a faster duration type of QX-314-resistant spikes were observed. The former had high thresholds, while the latter was activated at moderate depolarized levels. The slower and the faster QX-314-resistant spikes fired at frequencies up to 8/s and 35/s and were 35-60 and 5-10 ms in duration, respectively. With Cs+ loading, pyramidal neurons depolarized and slow, presumably Ca2+, and fast Na+ spikes widened. Fast spikes usually showed a prominent shoulder and a slower repolarization. No differences were observed between drug effects in CA1 and CA3 neurons. In terms of their possible participation in theta rhythm genesis the slow QX-314-resistant events display the correct frequency and duration and can oscillate regeneratively.
Nuñez
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Departamento de Morfologia, Facultad de Medicina UAM, Madrid, Spain.
Buño
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D000779:Anesthetics, Local / Q000494:pharmacology*; D000818:Animals; D002586:Cesium / Q000494:pharmacology*; D002712:Chlorides; D004558:Electric Stimulation; D006624:Hippocampus / Q000187:drug effects / Q000502:physiology*; D008012:Lidocaine / Q000031:analogs & derivatives* / Q000494:pharmacology; D008564:Membrane Potentials / Q000187:drug effects; D009474:Neurons / Q000187:drug effects / Q000502:physiology*; D011712:Pyramidal Tracts / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D011919:Rats, Inbred Strains; D013997:Time Factors
D000779:Anesthetics, Local; D002712:Chlorides; D002586:Cesium; C012647:QX-314; D008012:Lidocaine; C028019:cesium chloride