Quantitative distribution of GABA-immunopositive and-immunonegative neurons and synapses in the monkey striate cortex (Area 17)

C. Beaulieu, Z. Kisvárday, P. Somogyi, M. Cynader, A. Cowey

Research output: Contribution to journalArticle

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Abstract

The number of GABA-immunoreactive [GABA(+)] neurons and synapses was determined in functionally distinct subregions delineated as rich and poor in cytochrome oxidase (CO) in the visual cortex of adult macaque monkeys. The average numerical density (number per unit volume, NV) of GABA(+) neurons and synapses was not significantly different between the CO-rich and -poor regions. Twenty percent of the total number of cortical neurons and 17% of the synapses were GABA(+). On average, each visual cortical neuron receives 3900 synapses, 660 of them being GABA(+). The latter were distributed on the target cell in a pattern that predicts the site of GABA influences in cortex. The major targets of GABA(+) synapses were dendritic shafts, comprising nearly two-thirds of the postsynaptic elements. About every fourth and every eighth GABA(+) synapse was devoted to dendritic spines and to neuronal somata, respectively. Axon initial segments, although the exclusive targets of GABA(+) cells, comprise less than 0.1% of structures postsynaptic to GABA(+) boutons. From this distribution, we estimate that in each cubic millimeter of striate cortex there were about 20 million GABA(+) synapses on dendritic spines, 47 million on dendritic trunks, 9 million on somata, and fewer than 0.1 million on axon initial segments. The sites of influences of GABA-immunonegative [GABA(-)] synapses were different in that they target mainly dendritic spines and dendritic trunks. About two-thirds of GABA(-) synapses were on dendritic spines, and the remainder were devoted to dendritic trunks. Only a minute fraction innervate somata. We estimate that in 1 mm3 of striate cortex there were about 235 million GABA(-) synapses on spines, 133 million on dendrites, and about 2 million on somata. The proportions of GABA(+) neurons and synapses and their target distribution did not appreciably differ from those of the visual cortex of the cat even though the numerical density of neurons was 2.5 times higher in the monkey.

Original languageEnglish
Pages (from-to)295-309
Number of pages15
JournalCerebral Cortex
Volume2
Issue number4
Publication statusPublished - 1992

Fingerprint

Synapse
Visual Cortex
Cortex
Synapses
gamma-Aminobutyric Acid
Neurons
Haplorhini
Neuron
Spine
GABAergic Neurons
Dendritic Spines
Carisoprodol
Target
Electron Transport Complex IV
Unit of volume
Dendrite
Cell
Macaca
Dendrites
Remainder

ASJC Scopus subject areas

  • Neuroscience(all)
  • Statistics, Probability and Uncertainty
  • Applied Mathematics
  • Public Health, Environmental and Occupational Health
  • Molecular Biology
  • Cellular and Molecular Neuroscience
  • Cognitive Neuroscience

Cite this

Quantitative distribution of GABA-immunopositive and-immunonegative neurons and synapses in the monkey striate cortex (Area 17). / Beaulieu, C.; Kisvárday, Z.; Somogyi, P.; Cynader, M.; Cowey, A.

In: Cerebral Cortex, Vol. 2, No. 4, 1992, p. 295-309.

Research output: Contribution to journalArticle

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