title: Electrophysiological and morphological properties of pyramidal and nonpyramidal neurons in the cat motor cortex in vitro.
abstract: Electrophysiological and morphological properties of the neurons in cat motor cortex were investigated using intracellular recording and staining techniques in a brain slice preparation. In response to intracellular injection of depolarizing current pulses, four distinct types of firing patterns were observed among cat neocortical neurons. Regular-spiking neurons were characterized by their repetitive firing from which conspicuous frequency adaptation was observed. Doublet-or-burst firing cells were marked with their tendency to fire 2-5 clustered spikes at the onset of depolarizing pulse. In doublet-or-burst firing neurons, but not in regular-spiking neurons, a low-threshold calcium current was revealed by single-electrode voltage clamp. Both regular-spiking and doublet-or-burst firing neurons had relatively wide action potentials. Fast-spiking neurons could fire extremely narrow action potentials at a very high frequency. Their frequency-to-intensity slope of steady-state firing was significantly higher than that of the other neurons. In contrast, narrow-spiking neurons had the smallest frequency-to-intensity slope for steady-state firing, although their action potentials were as narrow as those of the fast-spiking neurons. Both regular-spiking and doublet-or-burst firing neurons were identified as pyramidal neurons, and were found in all layers below layer I. Their apical dendrites were densely coated with dendritic spines. Narrow-spiking neurons were only recorded in layer V. They were large pyramidal cells with scare spines on their apical dendrites. Fast-spiking neurons were all nonpyramidal interneurons. Seven out of eight labelled fast-spiking cells had beaded dendrites without spines. Their axons had a large number of varicosities, and arborized extensively to form a dense plexus of terminals in the vicinity of their soma. The remaining neuron was found to be a spiny nonpyramidal neuron in layer V. These results demonstrate that, in addition to the three types of firing patterns previously identified in rodent neocortex, a group of neurons in the cat motor cortex express another type of firing behaviour which is characterized by extremely narrow action potential and very small frequency-to-intensity slope. Correlation with the morphological data shows that these neurons are large layer V pyramidal cells rather than nonpyramidal interneurons.
authors.affiliation: Shanghai Brain Research Institute, Chinese Academy of Sciences, P.R. China.
authors.forename: W
authors.initials: W
authors.lastname: Chen
authors.forename: J J
authors.initials: JJ
authors.lastname: Zhang
authors.forename: G Y
authors.initials: GY
authors.lastname: Hu
authors.forename: C P
authors.initials: CP
authors.lastname: Wu
mesh_terms: D000200:Action Potentials / Q000187:drug effects / Q000502:physiology; D000818:Animals; D001369:Axons / Q000187:drug effects / Q000502:physiology / Q000648:ultrastructure; D002415:Cats; D003712:Dendrites / Q000187:drug effects / Q000502:physiology / Q000648:ultrastructure; D004594:Electrophysiology; D005260:Female; D066298:In Vitro Techniques; D007395:Interneurons / Q000187:drug effects / Q000502:physiology / Q000648:ultrastructure; D008239:Lysine / Q000031:analogs & derivatives; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D008854:Microscopy, Electron; D009044:Motor Cortex / Q000166:cytology / Q000502:physiology* / Q000648:ultrastructure*; D009474:Neurons / Q000187:drug effects / Q000502:physiology* / Q000648:ultrastructure*; D018408:Patch-Clamp Techniques; D017966:Pyramidal Cells / Q000187:drug effects / Q000502:physiology* / Q000648:ultrastructure*; D013779:Tetrodotoxin / Q000494:pharmacology
chemical_list: D013779:Tetrodotoxin; C013411:biocytin; D008239:Lysine