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Biol Psychiatry. 2017 Jul 1;82(1):40-48. doi: 10.1016/j.biopsych.2016.09.018. Epub 2016 Sep 29.

Alterations in a Unique Class of Cortical Chandelier Cell Axon Cartridges in Schizophrenia.

Author information

1
Department of Psychiatry, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania.
2
Department of Psychiatry, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania; Department Neuroscience, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania.
3
Department of Psychiatry, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania. Electronic address: fishkn@upmc.edu.

Abstract

BACKGROUND:

The axons of chandelier cells (ChCs) target the axon initial segment of pyramidal neurons, forming an array of boutons termed a cartridge. In schizophrenia, the density of cartridges detectable by gamma-aminobutyric acid (GABA) membrane transporter 1 immunoreactivity is lower, whereas the density of axon initial segments detectable by immunoreactivity for the α2 subunit of the GABAA receptor is higher in layers 2/superficial 3 of the prefrontal cortex. These findings were interpreted as compensatory responses to lower GABA levels in ChCs. However, we recently found that in schizophrenia, ChC cartridge boutons contain normal levels of the 67 kDa isoform of glutamic acid decarboxylase (GAD67) protein, the enzyme responsible for GABA synthesis in these boutons. To understand these findings we quantified the densities of ChC cartridges immunoreactive for vesicular GABA transporter (vGAT+), which is present in all cartridge boutons, and the subset of cartridges that contain calbindin (CB+).

METHODS:

Prefrontal cortex tissue sections from 20 matched pairs of schizophrenia and unaffected comparison subjects were immunolabeled for vGAT, GAD67, and CB.

RESULTS:

The mean density of vGAT+/CB+ cartridges was 2.7-fold higher, exclusively in layer 2 of schizophrenia subjects, whereas the density of vGAT+/CB- cartridges did not differ between subject groups. Neither vGAT, CB, or GAD67 protein levels per ChC bouton nor the number of boutons per cartridge differed between subject groups.

CONCLUSIONS:

Our findings of a greater density of CB+ ChC cartridges in prefrontal cortex layer 2 from schizophrenia subjects suggests that the normal developmental pruning of these cartridges is blunted in the illness.

KEYWORDS:

Axo-axonic cell; Development; GAD67; Gamma-aminobutyric acid; Quantitative microscopy; vGAT

PMID:
27884423
PMCID:
PMC5374057
DOI:
10.1016/j.biopsych.2016.09.018
[Indexed for MEDLINE]
Free PMC Article

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