Densities and Laminar Distributions of Kv3.1b-, PV-, GABA-, and SMI-32-Immunoreactive Neurons in Macaque Area V1

Cereb Cortex. 2019 May 1;29(5):1921-1937. doi: 10.1093/cercor/bhy072.

Abstract

The Kv3.1b potassium channel subunit is associated with narrow spike widths and fast-spiking properties. In macaque primary visual cortex (V1), subsets of neurons have previously been found to be Kv3.1b-immunoreactive (ir) but not parvalbumin (PV)-ir or not GABA-ir, suggesting that they may be both fast-spiking and excitatory. This population includes Meynert cells, the large layer 5/6 pyramidal neurons that are also labeled by the neurofilament antibody SMI-32. In the present study, triple immunofluorescence labeling and confocal microscopy were used to measure the distribution of Kv3.1b-ir, non-PV-ir, non-GABA-ir neurons across cortical depth in V1, and to determine whether, like the Meynert cells, other Kv3.1b-ir excitatory neurons were also SMI-32-ir pyramidal neurons. We found that Kv3.1b-ir, non-PV-ir, non-GABA-ir neurons were most prevalent in the M pathway-associated layers 4 Cα and 4B. GABAergic neurons accounted for a smaller fraction (11%) of the total neuronal population across layers 1-6 than has previously been reported. Of Kv3.1b-ir neurons, PV expression reliably indicated GABA expression. Kv3.1b-ir, non-PV-ir neurons varied in SMI-32 coimmunoreactivity. The results suggest the existence of a heterogeneous population of excitatory neurons in macaque V1 with the potential for sustained high firing rates, and these neurons were particularly abundant in layers 4B and 4 Cα.

Keywords: Kv3.1b potassium channel subunit; excitatory neurons; fast-spiking; parvalbumin; primary visual cortex.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Animals
  • Cell Count
  • Macaca fascicularis
  • Macaca mulatta
  • Male
  • Neurofilament Proteins / analysis*
  • Neurons / cytology*
  • Neurons / metabolism
  • Parvalbumins / analysis*
  • Shaw Potassium Channels / analysis*
  • Visual Cortex / cytology*
  • Visual Cortex / metabolism
  • gamma-Aminobutyric Acid / analysis*

Substances

  • Neurofilament Proteins
  • Parvalbumins
  • Shaw Potassium Channels
  • gamma-Aminobutyric Acid