Immunocytochemistry of glycine in small neurons of the granule cell areas of the guinea pig dorsal cochlear nucleus: a post-embedding ultrastructural study

The axon terminals of the acoustic nerve contact different part of the cochlear nucleus including granule cell areas. Little is known of the cell composition and neural circuits of granule cell areas present in the fusiform and upper polymorphic layers of the dorsal cochlear nucleus in the guinea pig. The present ultrastructural immunocytochemical study exploits the technique of post-embedding immunogold and silver intensification to reveal the characteristics of small neurons in granule cell areas. Few neurons (Golgi-stellate cells) use glycine as inhibitory neurotransmitter which is present in symmetric synaptic boutons with pleomorphic and flat vesicles. In contrast, most neurons (granule and unipolar brush cells) are not glycine-positive, and presumably not excitatory. Most of the large axons (mossy fibres) in granule areas are probably excitatory (glycine-negative and storing round synaptic vesicles) and contact unipolar brush cells forming large synapses or granule cell dendrites by small synapses. A few large glycinergic boutons (inhibitory) also contact unipolar brush cells. The excitatory circuit of mossy fibre-unipolar brush and granule cells may be inhibited by the glycinergic terminals from the few glycinergic cells (Golgi-stellate neurons) present within the granule cell areas. The latter are not contacted by large mossy-like glycine terminals.     

Development of Cerebellar Neurons and Glias Revealed by in Utero Electroporation: Golgi-Like Labeling of Cerebellar Neurons and Glias

Cerebellar cortical functions rely on precisely arranged cytoarchitectures composed of several distinct types of neurons and glias. Studies have indicated that cerebellar excitatory and inhibitory neurons have distinct spatial origins, the upper rhombic lip (uRL) and ventricular zone (VZ), respectively, and that different types of neurons have different birthdates. However, the spatiotemporal relationship between uRL/VZ progenitors and their final phenotype remains poorly understood due to technical limitations. To address this issue, we performed in utero electroporation (IUE) of fluorescent protein plasmids using mouse embryos to label uRL/VZ progenitors at specific developmental stages, and observed labeled cells at maturity. To overcome any potential dilution of the plasmids caused by progenitor division, we also utilized constructs that enable permanent labeling of cells. Cerebellar neurons and glias were labeled in a Golgi-like manner enabling ready identification of labeled cells. Five types of cerebellar neurons, namely Purkinje, Golgi, Lugaro and unipolar brush cells, large-diameter deep nuclei (DN) neurons, and DN astrocytes were labeled by conventional plasmids, whereas plasmids that enable permanent labeling additionally labeled stellate, basket, and granule cells as well as three types of glias. IUE allows us to label uRL/VZ progenitors at different developmental stages. We found that the five types of neurons and DN astrocytes were labeled in an IUE stage-dependent manner, while stellate, basket, granule cells and three types of glias were labeled regardless of the IUE stage. Thus, the results indicate the IUE is an efficient method to track the development of cerebellar cells from uRL/VZ progenitors facing the ventricular lumen. They also indicate that while the generation of the five types of neurons by uRL/VZ progenitors is regulated in a time-dependent manner, the progenitor pool retains multipotency throughout embryonic development.     

Widespread contribution of Gdf7 lineage to cerebellar cell types and implications for hedgehog-driven medulloblastoma formation

The roof plate is a specialized embryonic midline tissue of the central nervous system that functions as a signaling center regulating dorsal neural patterning. In the developing hindbrain, roof plate cells express Gdf7 and previous genetic fate mapping studies showed that these cells contribute mostly to non-neural choroid plexus epithelium. We demonstrate here that constitutive activation of the Sonic hedgehog signaling pathway in the Gdf7 lineage invariably leads to medulloblastoma. Lineage tracing analysis reveals that Gdf7-lineage cells not only are a source of choroid plexus epithelial cells, but are also present in the cerebellar rhombic lip and contribute to a subset of cerebellar granule neuron precursors, the presumed cell-of-origin for Sonic hedgehog-driven medulloblastoma. We further show that Gdf7-lineage cells also contribute to multiple neuronal and glial cell types in the cerebellum, including glutamatergic granule neurons, unipolar brush cells, Purkinje neurons, GABAergic interneurons, Bergmann glial cells, and white matter astrocytes. These findings establish hindbrain roof plate as a novel source of diverse neural cell types in the cerebellum that is also susceptible to oncogenic transformation by deregulated Sonic hedgehog signaling.     

Ptf1a, a bHLH transcriptional gene, defines GABAergic neuronal fates in cerebellum

The molecular machinery governing glutamatergic-GABAergic neuronal subtype specification is unclear. Here we describe a cerebellar mutant, cerebelless, which lacks the entire cerebellar cortex in adults. The primary defect of the mutant brains was a specific inhibition of GABAergic neuron production from the cerebellar ventricular zone (VZ), resulting in secondary and complete loss of external germinal layer, pontine, and olivary nuclei during development. We identified the responsible gene, Ptf1a, whose expression was lost in the cerebellar VZ but was maintained in the pancreas in cerebelless. Lineage tracing revealed that two types of neural precursors exist in the cerebellar VZ: Ptf1a-expressing and -nonexpressing precursors, which generate GABAergic and glutamatergic neurons, respectively. Introduction of Ptf1a into glutamatergic neuron precursors in the dorsal telencephalon generated GABAergic neurons with representative morphological and migratory features. Our results suggest that Ptf1a is involved in driving neural precursors to differentiate into GABAergic neurons in the cerebellum.     

Argyrophilic and Nitric Oxidergic Bipolar Neurons (Lugaro Cells) in Cerebellum of the Opisthocentrus Pholidapus dybowskii

Nitric oxidergic and argyrophilic Lugaro neurons were revealed in cerebellum of the opisthocentrus by using histochemical method of detection of NADPH-diaphorase and by Cajal impregnation. The argyrophilic cell population is located in the paleocerebellar part of the cerebellum. NADPH-D-positive Lugaro cells are revealed in the base of the cerebellar body, in the lateral prominence of granular eminence and a slight portion, in the paleocerebellar area. Neurons of the two populations form different types of junctions with each other as well as with Golgi cells and axons of basket neurons. It is possible that, with participation of NO molecules, they take part in formation of inhibitory processes in the cerebellum.     

SMAD4 is essential for generating subtypes of neurons during cerebellar development

Cerebellum development involves the coordinated production of multiple neuronal cell types. The cerebellar primordium contains two germinative zones, the rhombic lip (RL) and the ventricular zone (VZ), which generate different types of glutamatergic and GABAergic neurons, respectively. What regulates the specification and production of glutamatergic and GABAergic neurons as well as the subtypes for each of these two broad classes remains largely unknown. Here we demonstrate with conditional genetic approaches in mice that SMAD4, a major mediator of BMP and TGFβ signaling, is required early in cerebellar development for maintaining the RL and generating subsets of RL-derived glutamatergic neurons, namely neurons of the deep cerebellar nuclei, unipolar brush cells, and the late cohort of granule cell precursors (GCPs). The early cohort of GCPs, despite being deficient for SMAD4, is still generated. In addition, the numbers of GABAergic neurons are reduced in the mutant and the distribution of Purkinje cells becomes abnormal. These studies demonstrate a temporally and spatially restricted requirement for SMAD4 in generating subtypes of cerebellar neurons.     

Cerebellar localization and colocalization of GABA and calcium binding protein-D28K

Immunocytochemical studies using antibodies raised against the inhibitory neurotransmitter, gamma-aminobutyric acid (GABA) and against the 28 Kd vitamin D dependent calcium binding protein (calbindin) in the cerebellum, are reviewed. The GABA immunoreactive neurones found in the cerebellar cortex were the Purkinje cell (PC), the three classes of intrinsic inhibitory interneurones, stellate, basket and Golgi cells and the cells of Lugaro. Some of the neurons of the cerebellar nuclei were also found to be GABA immunoreactive. A part of these could be identified as extrinsic neurones projecting either back to the cerebellar cortex, or to the inferior olive, both these pathways being topographically highly organized but arising from independent parent neurons. The presumed inhibitory function of these two pathways are discussed. Calbindin immunoreactivity in the cerebellum was confined to the PCs, staining concerned the whole cell including soma, branching dendrites, axons and axons terminals. The antibody, which appears to be tightly bound to the PC in vivo, failed to stain some of the PC when cerebellar slices maintained in vitro were studied. The stability of the antigen-antibody binding and the use of calbindin as a marker specific for the PC in the cerebellum, is discussed. Co-localization of GABA with calbindin as well as with other calcium binding proteins are reported to be found in the PCs. While these co-localizations have led to much speculation, conclusive functional roles for them have not been identified at present.     

Localization of Hexokinase in Neural Tissue: Electron Microscopic Studies of Rat Cerebellar Cortex

: The distribution of hexokinase (ATP:d -hexose 6-phosphotransferase, EC 2.7.1.1) in the rat cerebellar cortex has been studied at the electron microscopic level using the peroxidase-antiperoxidase procedure. Extensive staining of cytoplasmic regions, with some increased staining at mitochondrial profiles, was seen in the cell bodies of both neurons (basket, stellate, Lugaro, Golgi, and granule cells) and astrocytes. Oligodendrocytes showed little or no detectable staining. Purkinje cell perikarya were much less intensely stained than were the perikarya of other neurons. The initial portion of the Purkinje dendrite was, like the perikaryon from which it emerged, lightly stained. More intense staining was seen in the secondary and tertiary branches of the Purkinje dendrite, but the terminal branches were devoid of stain. Granule cell dendrites were well stained in their initial portions but devoid of stain in their terminal dendritic digits which form part of the cerebellar glomeruli. In contrast to the unstained granule cell dendritic digits, the central mossy fiber nerve terminal of the glomerulus exhibited intense staining of the mitochondrial profiles and of synaptic vesicles adjacent to the mitochondria. Axons of basket cells showed intense staining in the segments adjacent to the Purkinje cell soma, while terminal twigs of the basket axons in the pinceau surrounding the (unstained) initial segment of the Purkinje axon showed markedly decreased staining intensity. These results indicate that there may be substantial variation in hexokinase levels between the various regions of neuronal processes. Hexokinase was seen at both cytoplasmic and mitochondrial locations in a variety of cells. It does not appear likely that location of hexokinase can be directly correlated with cell type, i.e., with neurons versus glia.     

Atrial natriuretic peptide-like immunoreactivity in neurons and astrocytes of human cerebellum and inferior olivary complex.

Atrial natriuretic peptide (ANP) has previously been localized in areas of mammalian brain associated with olfaction, cardiovascular function, and fluid/electrolyte homeostasis. Despite the presence of several types of natriuretic peptide receptors in mammalian cerebellum, neither intrinsic nor extrinsic sources of the natriuretic peptides have been described. In this report we describe the immunohistochemical localization of both intrinsic and extrinsic sources for ANP in human cerebellum. ANP-like immunoreactivity (ANP-LIR) was observed in climbing fibers in the cerebellar molecular layer that probably originated from isolated immunopositive neurons of the inferior olivary complex. Intrinsic sources of ANP-LIR included small subpopulations of protoplasmic and fibrous astrocytes and Bergmann glia, as well as Golgi and Lugaro neurons of the granule cell layer. These results suggest that, in addition to its presumptive roles in local vasoregulation, ANP may serve as a modulator of the activity of Purkinje neurons.     

The influence of the auditory cortex on acoustically evoked cerebellar responses in the CF-FM bat,Rhinolophus pearsonic chinesis

1. Acoustically evoked responses of 284 neurons isolated from the cerebellar vermis, hemispheres and paraflocculus of Rhinolophus pearsonic chinesis were studied under free field acoustic stimulation conditions. 2. The BFs of these cerebellar auditory neurons ranged from 24 to 76 kHz but they mostly fall either between 48 and 64 kHz or between 65 and 76 kHz. However, the BF distribution varies among vermal, hemispheric and parafloccular neurons. 3. Threshold curves of cerebellar neurons are generally broad but those tuned to the frequency of the predominant CF component are extremely narrow. 4. Response latencies of cerebellar neurons ranged from 2 to 48 ms suggesting multiple auditory cerebellar pathways. The latency distribution also varies among vermal, hemispheric and parafloccular neurons. 5. Although both the vermis and hemispheres contain a disproportionate number of 65-74 kHz neurons, the response latencies of those neurons isolated from the vermis are scattered over a wide range of 2.2-28 ms while those neurons isolated from the hemispheres are generally stabilized between 5 and 12 ms. 6. Electrical stimulation of the auditory cortex evokes discharges from a recorded cerebellar auditory neuron. Cortical stimulation also facilitates the response of an acoustically evoked cerebellar neuron by increasing its number of impulses. The degree of facilitation is dependent upon the amplitude of the acoustic stimulus. 7. For a given electrical and acoustic stimulation condition, the facilitative latency and the degree of facilitation varied with the interstimulus interval. Among 23 neurons studied, most of them (19 neurons, 82.6%) had a maximal facilitative latency between 2 and 10 ms. 8. By examining the difference in the facilitative effect in each isolated cerebellar auditory neuron before and after a topical application of local anesthetic, procaine, onto the point of electrical stimulation in the auditory cortex, we found that the facilitative pathways to vermal and hemispheric neurons may be different from the pathway to parafloccular neurons. 9. Possible auditory pathways to different parts of the cerebellum are discussed in relation to the wide range of recorded response latencies. 10. The facilitative influence of the auditory cortex on the cerebellar auditory neurons is assumed to enhance the cerebellar role in acoustic motor orientation.     

3D Reconstruction and Standardization of the Rat Vibrissal Cortex for Precise Registration of Single Neuron Morphology

The three-dimensional (3D) structure of neural circuits is commonly studied by reconstructing individual or small groups of neurons in separate preparations. Investigation of structural organization principles or quantification of dendritic and axonal innervation thus requires integration of many reconstructed morphologies into a common reference frame. Here we present a standardized 3D model of the rat vibrissal cortex and introduce an automated registration tool that allows for precise placement of single neuron reconstructions. We (1) developed an automated image processing pipeline to reconstruct 3D anatomical landmarks, i.e., the barrels in Layer 4, the pia and white matter surfaces and the blood vessel pattern from high-resolution images, (2) quantified these landmarks in 12 different rats, (3) generated an average 3D model of the vibrissal cortex and (4) used rigid transformations and stepwise linear scaling to register 94 neuron morphologies, reconstructed from in vivo stainings, to the standardized cortex model. We find that anatomical landmarks vary substantially across the vibrissal cortex within an individual rat. In contrast, the 3D layout of the entire vibrissal cortex remains remarkably preserved across animals. This allows for precise registration of individual neuron reconstructions with approximately 30 µm accuracy. Our approach could be used to reconstruct and standardize other anatomically defined brain areas and may ultimately lead to a precise digital reference atlas of the rat brain.     

Immunohistochemical localization of P-glycoprotein in rat brain and detection of its increased expression by seizures are sensitive to fixation and staining variables.

The MDR1 gene product, P-glycoprotein (P-gp), was shown to confer multidrug resistance to cancer cells, but its overexpression is also suggested to be involved in pharmacoresistance of epilepsy by acting as an energy-dependent drug-efflux pump in the blood-brain barrier (BBB). In normal brain tissue, P-gp is almost exclusively expressed by capillary endothelial cells (EC) of the BBB, whereas little or no expression is detected in other cell types. Increased P-gp expression was observed after seizures, but localization of this increase, i.e., within brain capillary EC or within parenchymal or perivascular astrocytes, which contribute to the BBB function, is controversial. To test whether these antithetic data arise from unusual properties of the antigen itself, we compared different immunohistochemical techniques and monoclonal or polyclonal antibodies to P-gp in normal rat brain and rat brain after kainate-induced seizures. Using acetone-fixed cryostat sections of snap-frozen tissue, strong P-gp labeling was detected in EC and, after seizures, in hippocampal neurons, but not in astrocytes. In contrast, EC and neuronal P-gp immunolabeling were not seen in paraformaldehyde-fixed sections, whereas both perivascular and parenchymal astrocytes exhibited strong P-gp labeling after seizures. The lack of P-gp labeling in EC by paraformaldehyde fixation, was reversed by treatment of the sections with acetate/ethanol. These experiments demonstrate that various fixation conditions have a striking effect on the immunohistochemical localization of P-gp in rat brain and detection of its increased expression by seizures. When data obtained from different immunohistochemical techniques are taken together, seizures seem to induce overexpression of P-gp in four different cell types, i.e., EC, perivascular astrocytes, parenchymal astrocytes, and neurons.     

Cerebellar globular cells receive monoaminergic excitation and monosynaptic inhibition from Purkinje cells

Inhibitory interneurons in the cerebellar granular layer are more heterogeneous than traditionally depicted. In contrast to Golgi cells, which are ubiquitously distributed in the granular layer, small fusiform Lugaro cells and globular cells are located underneath the Purkinje cell layer and small in number. Globular cells have not been characterized physiologically. Here, using cerebellar slices obtained from a strain of gene-manipulated mice expressing GFP specifically in GABAergic neurons, we morphologically identified globular cells, and compared their synaptic activity and monoaminergic influence of their electrical activity with those of small Golgi cells and small fusiform Lugaro cells. Globular cells were characterized by prominent IPSCs together with monosynaptic inputs from the axon collaterals of Purkinje cells, whereas small Golgi cells or small fusiform Lugaro cells displayed fewer and smaller spontaneous IPSCs. Globular cells were silent at rest and fired spike discharges in response to application of either serotonin (5-HT) or noradrenaline. The two monoamines also facilitated small Golgi cell firing, but only 5-HT elicited firing in small fusiform Lugaro cells. Furthermore, globular cells likely received excitatory monosynaptic inputs through mossy fibers. Because globular cells project their axons long in the transversal direction, the neuronal circuit that includes interplay between Purkinje cells and globular cells could regulate Purkinje cell activity in different microzones under the influence of monoamines and mossy fiber inputs, suggesting that globular cells likely play a unique modulatory role in cerebellar motor control.     

Immunoelectron microscopic localization of the neural cell adhesion molecules L1 and N-CAM during postnatal development of the mouse cerebellum

The cellular and subcellular localization of the neural cell adhesion molecules L1 and N-CAM was studied by pre- and postembedding immunoelectron microscopic labeling procedures in the developing mouse cerebellar cortex. The salient features of the study are: L1 displays a previously unrecognized restricted expression by particular neuronal cell types (i.e., it is expressed by granule cells but not by stellate and basket cells) and by particular subcellular compartments (i.e., it is expressed on axons but not on dendrites or cell bodies of Purkinje cells). L1 is always expressed on fasciculating axons and on postmitotic, premigratory, and migrating granule cells at sites of neuron-neuron contact, but never at contact sites between neuron and glia, thus strengthening the view that L1 is not involved in granule cell migration as a neuron-glia adhesion molecule. While N-CAM antibodies reacting with the three major components of N-CAM (180, 140, and 120 kD) show a rather uniform labeling of all cell types, antibodies to the 180-kD component (N-CAM180) stain only the postmigratory granule cell bodies supporting the notion that N-CAM180, the N-CAM component with the longest cytoplasmic domain, is not expressed before stable cell contacts are formed. Furthermore, N-CAM180 is only transiently expressed on Purkinje cell dendrites. N-CAM is present in synapses on both pre- and post-synaptic membranes. L1 is expressed only preterminally and not in the subsynaptic membranes. These observations indicate an exquisite degree of fine tuning in adhesion molecule expression during neural development and suggest a rich combinatorial repertoire in the specification of cell surface contacts.     

Glutamate, GABA and acetylcholine signaling components in the lamina of the Drosophila visual system

Synaptic connections of neurons in the Drosophila lamina, the most peripheral synaptic region of the visual system, have been comprehensively described. Although the lamina has been used extensively as a model for the development and plasticity of synaptic connections, the neurotransmitters in these circuits are still poorly known. Thus, to unravel possible neurotransmitter circuits in the lamina of Drosophila we combined Gal4 driven green fluorescent protein in specific lamina neurons with antisera to gamma-aminobutyric acid (GABA), glutamic acid decarboxylase, a GABA(B) type of receptor, L-glutamate, a vesicular glutamate transporter (vGluT), ionotropic and metabotropic glutamate receptors, choline acetyltransferase and a vesicular acetylcholine transporter. We suggest that acetylcholine may be used as a neurotransmitter in both L4 monopolar neurons and a previously unreported type of wide-field tangential neuron (Cha-Tan). GABA is the likely transmitter of centrifugal neurons C2 and C3 and GABA(B) receptor immunoreactivity is seen on these neurons as well as the Cha-Tan neurons. Based on an rdl-Gal4 line, the ionotropic GABA(A) receptor subunit RDL may be expressed by L4 neurons and a type of tangential neuron (rdl-Tan). Strong vGluT immunoreactivity was detected in alpha-processes of amacrine neurons and possibly in the large monopolar neurons L1 and L2. These neurons also express glutamate-like immunoreactivity. However, antisera to ionotropic and metabotropic glutamate receptors did not produce distinct immunosignals in the lamina. In summary, this paper describes novel features of two distinct types of tangential neurons in the Drosophila lamina and assigns putative neurotransmitters and some receptors to a few identified neuron types.     

Cell type-specific subunit composition of G protein-gated potassium channels in the cerebellum

G protein-gated inwardly rectifying potassium (GIRK/Kir3) channels regulate cellular excitability and neurotransmission. In this study, we used biochemical and morphological techniques to analyze the cellular and subcellular distributions of GIRK channel subunits, as well as their interactions, in the mouse cerebellum. We found that GIRK1, GIRK2, and GIRK3 subunits co-precipitated with one another in the cerebellum and that GIRK subunit ablation was correlated with reduced expression levels of residual subunits. Using quantitative RT-PCR and immunohistochemical approaches, we found that GIRK subunits exhibit overlapping but distinct expression patterns in various cerebellar neuron subtypes. GIRK1 and GIRK2 exhibited the most widespread and robust labeling in the cerebellum, with labeling particularly prominent in granule cells. A high degree of molecular diversity in the cerebellar GIRK channel repertoire is suggested by labeling seen in less abundant neuron populations, including Purkinje neurons (GIRK1/GIRK2/GIRK3), basket cells (GIRK1/GIRK3), Golgi cells (GIRK2/GIRK4), stellate cells (GIRK3), and unipolar brush cells (GIRK2/GIRK3). Double-labeling immunofluorescence and electron microscopies showed that GIRK subunits were mainly found at post-synaptic sites. Altogether, our data support the existence of rich GIRK molecular and cellular diversity, and provide a necessary framework for functional studies aimed at delineating the contribution of GIRK channels to synaptic inhibition in the cerebellum.     

Intracortical connections between neuron groups in the somatosensory cortex studied by the retrograde horseradish peroxidase transport method in rats

Short corticocortical connections between specialized groups of neurons (so-called barrels) were studied in the somatosensory cortex. After microinjections of horseradish peroxidase into a definite "barrel" labeled neurons were found in nearby groups within a radius of up to 400 µ. Labeled neurons were located chiefly in cortical layers V and III; 90% of them were pyramidal cells. Intracortical connection of labeled neurons were 1.6 times more numerous than thalamocortical connections. It is postulated that connections between neighboring cortical neuron groups are effected through their output cells, i.e., through pyramidal neurons of layers V and III.     

Insect optic lobe neurons identifiable with monoclonal antibodies to GABA

Five monoclonal antibodies against GABA were tested on glutaraldehyde fixed sections of optic lobes of three insect species, blowflies, houseflies and worker bees. The specificity of these antibodies was analyzed in several tests and compared with commercially available anti-GABA antiserum. A very large number of GABA-like immunoreactive neurons innervate all the neuropil regions of these optic lobes. Immunoreactive processes are found in different layers of the neuropils. The immunoreactive neurons are amacrines and columnar or noncolumnar neurons connecting the optic lobe neuropils. In addition some large immunoreactive neurons connect the optic lobes with centers of the brain. Some neuron types could be matched with neurons previously identified with other methods. The connections of a few of these neuron types are partly known from electron microscopy or electrophysiology and a possible role of GABA in certain neural circuits can be discussed.     

Insect optic lobe neurons identifiable with monoclonal antibodies to GABA

Summary Five monoclonal antibodies aginst GABA were tested on glutaraldehyde fixed sections of optic lobes of three insect species, blowflies, houseflies and worker bees. The specificity of these antibodies was analyzed in several tests and compared with commercially available anti-GABA antiserum.A very large number of GABA-like immunoreactive neurons inncrvate all the neuropil regions of these optic lobes. Immunoreactive processes are found in different layers of the neuropils. The immunoreactive neurons are amacrines and columnar or noncolumnar neurons connecting the optic lobe neuropils. In addition some large immunoreactive neurons connect the optic lobes with centers of the brain.Some neuron types could be matched with neurons previously identified with other methods. The connections of a few of these neuron types are partly known from electron microscopy or electrophysiology and a possible role of GABA in certain neural circuits can be discussed.     

人胎视皮质皮质下层NPY－IR神经元的发育

本文用免疫组化方法研究了１６周至足月人胎视皮质皮质下层ＮＰＹ－ＩＲ神经元的发育。各胎龄视皮质ＳＰ层内均有ＮＰＹ－ＩＲ神经元分布。从１６周至２６周,ＮＰＹ－ＩＲ神经元密度逐渐增高并于２６周达高峰;３２周以后阳性神经元密度随胎龄增长而下降。人胎视皮质ＳＰ层ＮＰＹ－ＩＲ神经元形态也随胎龄而变化;２０周以前,ＮＰＹ－ＩＲ神经元大多是胞体较小,突起短而少的未分化神经元、ＳＰ层内ＮＰＹ－ＩＲ纤维少。２０周以后,ＮＰＹ－ＩＲ神经元胞体增大,突起增多、变长;多极和双极、双簇神经元随胎龄增长而增多;ＳＰ层内的ＮＰＹ－ＩＲ纤维大量增加,部分纤维穿入皮质板。３２周以后,多极ＮＰＹ－ＩＲ神经元逐渐减少,双极双簇神经元所占比例相对增高。ＮＰＹ免疫组化结合ＮＡＤＰＨ－ｄ组化显示人胎视皮质ＳＰ层大多数ＮＰＹ－ＩＲ神经元同时呈ＮＯＳ阳性。本研究观察到人胎视皮质ＳＰ层内ＮＰＹ－ＩＲ神经元发育可分为发生、成熟和退化三个阶段。