Distinct classes of pyramidal cells exhibit mutually exclusive firing patterns in hippocampal area CA3b.
It is thought that CA3 pyramidal neurons communicate mainly through bursts of spikes rather than so-called trains of regular firing action potentials. Reports of both burst firing and nonburst firing CA3 cells suggest that they may fire with more than one output pattern. With the use of whole-cell recording methods we studied the firing properties of rat hippocampal pyramidal neurons in vitro within the CA3b subregion and found three distinct types of firing patterns. Approximately 37% of cells were regular firing where spikes generated by minimal current injection (rheobase) were elicited with a short latency and with stronger current intensities trains of spikes exhibited spike frequency adaptation (SFA). Another 46% of neurons exhibited a delayed onset at rheobase with a weakly-adapting firing pattern upon stronger stimulation. The remaining 17% of cells showed a burst-firing pattern, though only elicited in response to strong current injection and spontaneous bursts were never observed. Control experiments indicated that the distinct firing patterns were not due to our particular slicing methods or recording techniques. Finally, computer modeling was used to identify how relative differences in K+ conductances, specifically K(C), K(M), and K(D), between cells contribute to the different characteristics of the three types of firing patterns observed experimentally.
Hemond
Peter
P
Department of Biology, The University of Texas at San Antonio, San Antonio, Texas 78249, USA.
Epstein
Daniel
D
Boley
Angela
A
Migliore
Michele
M
Ascoli
Giorgio A
GA
Jaffe
David B
DB
D000200:Action Potentials / Q000502:physiology*; D000818:Animals; D002462:Cell Membrane / Q000502:physiology*; D003198:Computer Simulation; D006624:Hippocampus / Q000502:physiology*; D008959:Models, Neurological; D009434:Neural Pathways / Q000502:physiology; D009924:Organ Culture Techniques; D018408:Patch-Clamp Techniques; D015221:Potassium Channels / Q000502:physiology*; D017966:Pyramidal Cells / Q000166:cytology / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D011930:Reaction Time / Q000502:physiology; D013569:Synapses / Q000502:physiology; D009435:Synaptic Transmission / Q000502:physiology; D013997:Time Factors
D015221:Potassium Channels