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Long-range GABAergic projection neurons in the cat neocortex
Shigeyoshi Higo1, Naoko Udaka, Nobuaki Tamamaki
1Department of Morphological Neural Science, Graduate School of Medical Sciences, Kumamoto University, Kumamoto 860-8556, Japan. neuro2@kaiju.medic.kumamoto-u.ac.jp
The Journal of Comparative Neurology
|May 16, 2007
Summary
Long-range projecting gamma-aminobutyric acid (GABA)ergic neurons were identified in the cat neocortex. These GABAergic projection neurons, found in deep cortical layers, exhibit unique long-range projections, expanding our understanding of cortical circuitry.
Area of Science:
- Neuroscience
- Cortical Circuitry
- Neuroanatomy
Background:
- Neocortical gamma-aminobutyric acid (GABA)ergic neurons traditionally function in local circuits.
- Recent murine studies revealed GABAergic neurons with long-range projections.
- The presence of such neurons in feline neocortex remained uninvestigated.
Purpose of the Study:
- To investigate the existence and characteristics of GABAergic projection neurons in the cat neocortex.
- To determine if GABAergic neurons in cats exhibit long-range projections similar to those found in mice.
- To characterize the neurochemical profile of these projection neurons.
Main Methods:
- Wheat germ agglutinin-conjugated horseradish peroxidase (WGA-HRP) injections into visual, auditory, or somatosensory cortex.
- Retrograde and orthograde labeling of efferent cortical neurons, axons, and terminals.
- Staining for nicotinamide adenine dinucleotide phosphate diaphorase (NADPH-d) and co-localization with WGA-HRP using microscopy.
Main Results:
- Identified double-labeled neurons (WGA-HRP and NADPH-d) in cortical layers VIa, VIb, and white matter, indicating GABAergic neurons with long-range projections.
- Intensely NADPH-d-reactive neurons (type I) were neuronal nitric oxide synthase (nNOS) positive.
- Weakly NADPH-d-reactive neurons (type II) lacked nNOS; nNOS often co-localized with GABA, neuropeptide-Y, and somatostatin.
Conclusions:
- GABAergic neurons in the cat neocortex possess long-range projection capabilities, similar to principal neurons.
- Unique GABAergic long-range projections were demonstrated in the feline brain.
- These findings contribute to a more comprehensive understanding of neocortical network organization and function.
