Cytoarchitecture of nitrergic neurons in the human striatum and subthalamic nucleus

Morphology and morphometry of interneuron subpopulations of the marmoset monkey (Callithrix jacchus) striatum

The mammalian striatum has long been considered a homogeneous entity. However, neuroanatomical and histochemical studies reveal that the striatum is much more heterogeneous than previously suspected. The caudate (Cd) and putamen (Pu) are composed of two chemical compartments: the matrix and the striosomes. Striatal interneurons have been classified into a variety of morphological and neurochemical subtypes. In this study, we compared the distribution of multiple neurochemical markers in the striatum of marmosets and described the morphology of different types of striatum interneurons. The immunoreactivities of choline-acetyl transferase (ChAT), neuropeptide Y (NPY), nitric oxide synthase (NOS), calretinin (CR), parvalbumin (PV) were analyzed along the entire rostrocaudal extent of the marmoset striatum. Calbindin immunohistochemistry is useful in identifying medium spiny neurons (MSNs), with efficient soma staining. Based on the size of the CB-positive cells, considered medium-sized, as expected, cholinergic cells are larger in area and diameter than the other subpopulations investigated, followed by NOS, NPY, PV and CR. In adjacent CB and PV-stained sections, the matrix and striosomes were clearly distinguished. The matrix is strongly reactive to CB and PV neuropils, while the striosomes exhibit low reactivity, especially in the dorsal Cd. Therefore, we provide a detailed description morphology and distribution of striatal interneuron populations in a model as a valuable tool for studying neurodegenerative pathogenesis, progression and treatment strategies.

The Stereological Analysis and Spatial Distribution of Neurons in the Human Subthalamic Nucleus

The subthalamic nucleus (STN) is a small, ovoid structure, and an important site of deep brain stimulation (DBS) for the treatment of Parkinson’s disease. Although the STN is a clinically important structure, there are many unresolved issues with regard to it. These issues are especially related to the anatomical subdivision, neuronal phenotype, neuronal composition, and spatial distribution. In this study, we have examined the expression pattern of 8 neuronal markers [nNOS, NeuN, parvalbumin (PV), calbindin (CB), calretinin (CR), FOXP2, NKX2.1, and PAX6] in the adult human STN. All of the examined markers, except CB, were present in the STN. To determine the neuronal density, we have performed stereological analysis on Nissl-stained and immunohistochemical slides of positive markers. The stereology data were also used to develop a three-dimensional map of the spatial distribution of neurons within the STN. The nNOS population exhibited the largest neuronal density. The estimated total number of nNOS STN neurons is 281,308 ± 38,967 (± 13.85%). The STN neuronal subpopulations can be divided into two groups: one with a neuronal density of approximately 3,300 neurons/mm³ and the other with a neuronal density of approximately 2,200 neurons/mm³. The largest density of STN neurons was observed along the ventromedial border of the STN and the density gradually decreased toward the dorsolateral border. In this study, we have demonstrated the presence of 7 neuronal markers in the STN, three of which were not previously described in the human STN. The human STN is a collection of diverse, intermixed neuronal subpopulations, and our data, as far as the cytoarchitectonics is concerned, did not support the tripartite STN subdivision.

Levodopa-induced dyskinesias in Parkinson's disease increase cerebrospinal fluid nitric oxide metabolites' levels

Levodopa-induced dyskinesia (LID) is a common complication of Parkinson's disease (PD) therapy. Nitric oxide in the central nervous system may have a role in its pathophysiology. The present work investigates plasma and CSF levels of nitric oxide metabolites nitrite and nitrate in patients with PD, LID, and healthy control. We measured plasma and CSF nitrite and nitrate levels in patients with PD with and without LID and in healthy controls. The levels of plasma and CSF nitrite and nitrate were measured by ozone-based chemiluminescence. Sixty-seven participants were enrolled. CSF nitrite levels in patients with PD and LID were higher than in patients with PD without LID and healthy controls. CSF/plasma ratio of nitrite was higher in patients with PD and LID than in patients with PD without LID. The CSF/plasma ratio of nitrite in patients with PD and LID was higher than 1, indicating an intrathecal production of NO in patients with this motor complication. There was an increase in nitrate levels of CSF and CSF/plasma ratio of nitrate in patients with PD and LID compared to the healthy controls. Sex, age at evaluation, disease duration, and levodopa equivalent daily doses, as well as processing and storage time, did not critically influence these results. The present study demonstrated an increase in nitrite and nitrate levels in the central nervous system of patients with PD and LID. This finding strengthens the role of NO on LID pathophysiology.

Pattern of nitrergic cells and fibers organization in the central nervous system of the Australian lungfish, Neoceratodus forsteri (Sarcopterygii: Dipnoi)

The Australian lungfish Neoceratodus forsteri is the only extant species of the order Ceratodontiformes, which retained most of the primitive features of ancient lobe finned-fishes. Lungfishes are the closest living relatives of land vertebrates and their study is important for deducing the neural traits that were conserved, modified, or lost with the transition from fishes to land vertebrates. We have investigated the nitrergic system with neural nitric oxide synthase (NOS) immunohistochemistry and NADPH-diaphorase (NADPH-d) histochemistry, which yielded almost identical results except for the primary olfactory projections and the terminal and preoptic nerve fibers labeled only for NADPH-d. Combined immunohistochemistry was used for simultaneous detection of NOS with catecholaminergic, cholinergic, and serotonergic structures, aiming to establish accurately the localization of the nitrergic elements and to assess possible interactions between these neurotransmitter systems. The results demonstrated abundant nitrergic cells in the basal ganglia, amygdaloid complex, preoptic area, basal hypothalamus, mesencephalic tectum and tegmentum, laterodorsal tegmental nucleus, reticular formation, spinal cord, and retina. In addition, low numbers of nitrergic cells were observed in the olfactory bulb, all pallial divisions, lateral septum, suprachiasmatic nucleus, prethalamic and thalamic areas, posterior tubercle, pretectum, torus semicircularis, cerebellar nucleus, interpeduncular nucleus, the medial octavolateral nucleus, nucleus of the solitary tract, and the dorsal column nucleus. Colocalization of NOS and tyrosine hydroxylase was observed in numerous cells of the ventral tegmental area/substantia nigra complex. Comparison with other vertebrates, using a neuromeric analysis, reveals that the nitrergic system of Neoceratodus shares many neuroanatomical features with tetrapods and particularly with amphibians.