In vivo electrophysiological analysis of lucifer yellow-coupled hippocampal pyramids.
Small transient all-or-none depolarizations (also termed in the literature fast prepotentials, spikelets, pseudospikes, d-spikes, or short latency depolarizations) and their association with lucifer yellow (LY) dye-coupling were analyzed in CA1-CA3 hippocampal pyramidal cells in urethane anesthetized rats. It was found that (a) 15 of the 24 LY-injected pyramidal neurons (63%) showed dye-coupling; (b) spontaneous, anti- and orthodromically evoked spikelets (3-7 ms in duration; 3- to 12-mV peak) were recorded in 40 of 95 cells (42%); (c) there was a significantly higher probability of dye-coupled neurons with spikelets and of uncoupled ones without spikelets; (d) spikelet waveform and amplitude were unaffected by spontaneous or imposed polarizations; (e) large hyperpolarizations could reduce the rate and even prevent spikelets; and (f) spikelets could precede or follow spikes, the latter were more frequent with large depolarizations. Electrophysiological findings, and the association of dye-coupling and spikelets, suggest strongly that at least some spikelets are coupling potentials. This implies that pyramidal cells may be electronically coupled under physiological conditions.
Núñez
A
A
Departamento de Investigación, Hospital Ramón y Cajal, Madrid, Spain.
García-Austt
E
E
Buño
W
W
D000200:Action Potentials; D000818:Animals; D004553:Electric Conductivity; D004558:Electric Stimulation; D004594:Electrophysiology; D005071:Evoked Potentials; D005456:Fluorescent Dyes; D006624:Hippocampus / Q000166:cytology / Q000502:physiology*; D007546:Isoquinolines; D008564:Membrane Potentials; D008856:Microscopy, Fluorescence; D009474:Neurons / Q000502:physiology*; D011712:Pyramidal Tracts / Q000166:cytology / Q000502:physiology*; D051381:Rats; D011919:Rats, Inbred Strains
D005456:Fluorescent Dyes; D007546:Isoquinolines; C017475:lucifer yellow