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

• Published in: Cerebral cortex (New York, N.Y. 1991) Vol. 29; no. 5; pp. 1921 - 1937
• Main Authors: Kelly, Jenna G, García-Marín, Virginia, Rudy, Bernardo, Hawken, Michael J
• Format: Journal Article
• Language: English
• Published: United States Oxford University Press 01.05.2019
• Subjects: Animals; Cell Count; gamma-Aminobutyric Acid - analysis; Macaca fascicularis; Macaca mulatta; Male; Neurofilament Proteins - analysis; Neurons - cytology; Neurons - metabolism; Original; Parvalbumins - analysis; Shaw Potassium Channels - analysis; Visual Cortex - cytology; Visual Cortex - metabolism; Kv3.1b potassium channel subunit; primary visual cortex; excitatory neurons; fast-spiking; parvalbumin
• ISSN: 1047-3211; 1460-2199
• 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.