[show abstract][hide abstract] ABSTRACT: gamma-aminobutyric acid (GABA)ergic neurons in the neocortex have been regarded as interneurons and speculated to modulate the activity of neurons locally. Recently, however, several experiments revealed that neuronal nitric oxide synthase (nNOS)-positive GABAergic neurons project cortico-cortically with long axons. In this study, we illustrate Golgi-like images of the nNOS-positive GABAergic neurons using a nicotinamide adenine dinucleotide phosphate diaphorase (NADPH-d) reaction and follow the emanating axon branches in cat brain sections. These axon branches projected cortico-cortically with other non-labeled arcuate fibers, contra-laterally via the corpus callosum and anterior commissure. The labeled fibers were not limited to the neocortex but found also in the fimbria of the hippocampus. In order to have additional information on these GABAergic neuron projections, we investigated green fluorescent protein (GFP)-labeled GABAergic neurons in GAD67-Cre knock-in/GFP Cre-reporter mice. GFP-labeled axons emanate densely, especially in the fimbria, a small number in the anterior commissure, and very sparsely in the corpus callosum. These two different approaches confirm that not only nNOS-positive GABAergic neurons but also other subtypes of GABAergic neurons project long axons in the cerebral cortex and are in a position to be involved in information processing.
Frontiers in Neuroanatomy 01/2009; 3:25. · 4.06 Impact Factor
[show abstract][hide abstract] ABSTRACT: The cadaver of an 89-year-old woman who had died of cerebral apoplexy and which was dedicated to anatomy practice for medical students at Kumamoto University, was found to have complete lack of the right ventral root of the seventh cervical segment (C7). Observation of the peripheral spinal nerve indicated that the branch, which appeared to be a descending collateral of the ventral root of C6, became confluent with the dorsal root of C7 at the point just distal to the dorsal root ganglion. Following this confluence, new fiber elements ran out of the intervertebral foramen as the seventh cervical nerve. More peripherally, this fiber bundle joined the brachial plexus, its outward appearance was normal in the manner of ramification and each nerve's supply to muscles. Additionally, the inside view of the spinal cord of C6, C7 and C8 was examined neuroanatomically. Nissl staining of transverse sections at C7 (block 2) showed that motor neurons existed in the right anterior horn and their histological features were normal. Subsequently, horizontal sections were made from the two blocks, each of which contained C6/C7 (block 1) or C7/C8 (block 3), and were treated dually with Nissl and myelin staining. These sections also had a normal picture of cells and myelinated fibers on the right side as compared with those on the left side. The results suggested that motor neurons of the right C7 had a normal supply to the targets, although the trajectory of their axons in the spinal cord was obscure.
Anatomical science international / Japanese Association of Anatomists 10/2007; 82(3):133-8. · 0.63 Impact Factor
[show abstract][hide abstract] ABSTRACT: Neocortical gamma-aminobutyric acid (GABA)ergic neurons have been previously described as largely involved in local intracortical circuitry. However, our recent findings in the murine model described select neocortical GABAergic neurons that project to both neighboring and more distant neocortical regions. Here, we investigated whether such GABAergic projection neurons are also found in the cat neocortex. Wheat germ agglutinin-conjugated horseradish peroxidase (WGA-HRP) was injected into the visual, auditory, or somatosensory cortex, in order to label efferent cortical neurons retrogradely and to label axons and terminals orthogradely. Staining for nicotinamide adenine dinucleotide phosphate diaphorase (NADPH-d), an enzyme involved in nitric oxide synthesis, was employed, and co-localization with WGA-HRP was determined by means of both polarizing and brightfield microscopy. We concluded that neurons double-labeled with WGA-HRP and NADPH-d in a distant region from the WGA-HRP-injection site are GABAergic neurons with long-range projection axons. All double-labeled neurons were found in cortical layers VIa and VIb and in the white matter. Neurons with intense NADPH-d reactivity (type I) were determined to be neuronal nitric oxide synthase (nNOS) positive in all cases. However, weakly NADPH-d-reactive neurons (type II) lacked nNOS immunoreactivity. Moreover, nNOS often co-localized with GABA, neuropeptide-Y, and somatostatin in the cat neocortex. In summary, the GABAergic neurons described here projected in a manner similar to that previously described for neocortical principal neurons, although some unique GABAergic long-range projections were also demonstrated.
The Journal of Comparative Neurology 08/2007; 503(3):421-31. · 3.66 Impact Factor