Two functional inhibitory circuits are comprised of a heterogeneous population of fast-spiking cortical interneurons.
Cortical fast spiking (FS) interneurons possess autaptic, synaptic, and electrical synapses that serve to mediate a fast, coordinated response to their postsynaptic targets. While FS interneurons are known to participate in numerous and diverse actions, functional subgroupings within this multi-functional interneuron class remain to be identified. In the present study, we examined parvalbumin-positive FS interneurons in layer 4 of the primary somatosensory (barrel) cortex - a brain region well-known for specialized inhibitory function. Here we show that FS interneurons fall into two broad categories identified by the onset of the first action potential in a depolarizing train as: "delayed firing FS interneurons (FSD) and early onset firing FS interneurons (FSE). Subtle variations in action potential firing reveal six subtypes within these two categories: delayed non-accommodating (FSD-NAC), delayed stuttering (FSD-STUT), early onset stuttering (FSE-STUT), early onset-late spiking (FSE-LS), early onset early-spiking (FSE-ES), and early onset accommodating (FSE-AC). Using biophysical criteria previously employed to distinguish neuronal cell types, the FSD and FSE categories exhibit several shared biophysical and synaptic properties that coincide with the notion of specificity of inhibitory function within the cortical FS interneuron class.
Center for Neuroscience Research, Children's National Medical Center, Washington, DC 20010, USA.
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Department of Pharmaceutical Sciences, Skaggs School of Pharmacy, University of Colorado, Anschutz Medical Campus, Aurora, CO 80045, USA; Department of Pediatrics, School of Medicine, University of Colorado, Anschutz Medical Campus, Aurora, CO 80045, USA. Electronic address: Molly.Huntsman@UCDenver.edu.
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D000200:Action Potentials; D000818:Animals; D005260:Female; D007395:Interneurons / Q000378:metabolism / Q000502:physiology*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D009415:Nerve Net / Q000502:physiology*; D009433:Neural Inhibition / Q000502:physiology*; D010320:Parvalbumins / Q000378:metabolism; D013003:Somatosensory Cortex / Q000502:physiology*
D010320:Parvalbumins
basket cells; inhibitory neurotransmission; interneuron