Network of GABAergic large basket cells in cat visual cortex (area 18): Implication for lateral disinhibition

Zoltán F. Kisvárday, Clermont Beaulieu, Ulf T. Eysel

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Abstract

Anatomical and immunohistochemical data indicate that, in addition to pyramidal neurons, nonpyramidal cells are exposed to perisomatic inhibition mediated by γ‐aminobutyric acid (GABA)‐containing terminals. However, no direct information is available as yet for the origin of GABAergic inputs to morphologically identified GABAergic neurons. In the present paper, we studied the topographical and synaptic relationship between identified GABAergic large basket cells and their immunohistochemically characterized target neurons revealed by parvalbumin‐(PV) and GABA immunostaining in the same material. Extracellularly applied biocytin labelled a total of 36 and 9 large basket cells in layers III and V, respectively. Of these, the axonal arborizations of two basket cells, BC1 and BC2, were reconstructed. The axon of BC1 occupied an area of about 2.3 × 2.2 mm2 in layer III, providing a total of 2,755 terminals. The axon of BC2 showed an overall extent of 3.8 × 1.7 mm2 in layer V elongated in the anteroposterior direction, and gave off 1,599 terminals. Immunostaining for PV was carried out to reveal putative nonpyramidal targets for BC1 and BC2. It was found that in addition to immunonegative cells, they established an average of 4–6 perisomatic contacts onto each of 58 (BC1) and 33 (BC2) PV‐immunopositive neurons. For electron microscopic verification, 23 terminals apposing the somata of 12 PV‐immunopositive neurons were selected. Each terminal was found to establish symmetrical (type II) contacts with its targeted cell. Furthermore, the distribution of soma area of the targeted PV‐immunopositive cells and of identified large basket cells showed remarkable similarity, implying that the two populations were actually the same. In addition, the average horizontal distance between neighbouring PV‐immunopositive target cells was found to be about 100 μm both in layers III and V. The results suggest that in area 18 the same large basket cell provides direct inhibition to certain pyramidal cells and facilitation to other pyramidal neurons, by inhibiting their presynaptic large basket cells at regular intervals. 1993 Wiley‐Liss, Inc.

Original languageEnglish
Pages (from-to)398-415
Number of pages18
JournalJournal of Comparative Neurology
Volume327
Issue number3
DOIs
Publication statusPublished - Jan 15 1993

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Keywords

  • 3‐dimensional reconstruction
  • GABA immunostaining
  • calcium‐binding protein
  • electron microscopy

ASJC Scopus subject areas

  • Neuroscience(all)

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