Sympathetic Ganglion Cells Research Articles

Coexpression of endothelial PAS protein 1 with essential angiogenic factors suggests its involvement in human vascular development.

Endothelial PAS protein 1 (EPAS1) is a bHLH-PAS transcription factor involved in cellular response to hypoxia. Its precise role in angiogenesis is unclear, but several genes essential to vascular development, including those encoding vascular endothelial growth factor (VEGF), its receptor VEGFR-2 and Tie2, are thought to be targets of EPAS1. To investigate whether this transcription factor and its putative targets were expressed concomitantly, we performed in situ hybridization on serial adjacent sections of human embryos at gestational ages of 3 to 6 weeks. We studied expression of the genes encoding EPAS1, VEGF, VEGFR-1, and -2, Tie2, and its ligands, angiopoietin (Ang) 1 and 2. We also compared these expression profiles with that of hypoxia-inducible factor 1alpha (HIF1alpha). EPAS1 transcripts were detected in several types of endothelial cell: in blood vessels walls, the endocardium, the glomeruli of the mesonephros, and the sinusoids of the liver. In these endothelial cells, expression of EPAS1 systematically or partly coincided with Tie2 and the VEGF receptors expression. There was also some overlap between the sites of synthesis of EPAS1 and VEGF mRNAs, principally in hepatocytes and sympathetic ganglion cells. In addition, we found that EPAS1 and HIF1alpha transcripts were often colocalized, suggesting a functional redundancy of these two transcription factors during development. These observations are consistent with transactivation by EPAS1 of the expression of its putative target genes during embryogenesis, suggesting that this transcription factor is involved in human angiogenesis. They provide evidence that EPAS1 is involved in the regulation of vascular maturation, remodeling, or stabilization rather than in the early steps of embryonic angiogenesis.

Death of rat sympathetic ganglion cells in vitro caused by neurite transection: effect of extracellular calcium.

Calcium entry into neurons secondary to excitotoxic insults is believed to cause neuronal death after trauma and ischemia, but the role of calcium influx in neuronal death after neurite transection independent of excitotoxicity has not been clearly defined. This study assesses the effect of variations in extracellular calcium concentration ([Ca2+]e) from 50 nM to 5 mM on cell death, in 14-day-old cultures of dissociated sympathetic neurons from the superior cervical ganglia of newborn rats. The neurites were transected with a custom-made injury device, and cell death was assessed with propidium iodide and fluorescence microscopy. We found that neurite transection caused a significant increase (p < 0.05) in cell death at all [Ca2+]e studies, but there was no significant difference in mortality at the various [Ca2+]e. Cell death significantly increased between 2 and 24 h postinjury at all three [Ca2+]e. Cell death increased with decreasing distance between the cell body and the transection site, and there was a significant decrease in mortality at distances greater than 0.66 mm, irrespective of the [Ca2+]e. These results suggest that influx of extracellular calcium is not responsible for posttransection cell death, suggesting that calcium release from internal stores or calcium-independent cell death mechanisms are triggered by neurite transection.

The expression of Quox 1, a homeodomain-containing protein, in sympathetic ganglion cells is regulated in vitro by growth factors.

Quox 1, a quail homeobox gene, is the first vertebrate Antp-type homeobox gene to be described that is expressed in the forebrain. We have already shown that the Quox 1 protein is specifically expressed in post-mitotic sensory neurons. A subpopulation of sympathetic ganglion cells was also found to be labelled by anti-Quox 1 in vitro, but it is not clear whether this protein is expressed in sympathetic ganglion cells in vivo and, if so, the conditions which regulate its expression in vitro. In the present study, we used immunocytochemistry to find out whether Quox 1 expression in sympathetic ganglion cells in vitro is regulated by environmental signals. We found that several peptide growth factors can regulate Quox 1 expression in cultured sympathetic ganglion cells, and that they do so at physiological concentration and in a variety of ways. Basic fibroblast growth factor (FGF-2) induces Quox 1 protein expression, whereas insulin and human insulin-like growth factor-I (IGF-I) down-regulate Quox 1 expression.

Vesicle-associated proteins and transmitter release from sympathetic ganglionic boutons.

A method is reported for introducing peptides derived from SNARE proteins that control exocytosis of vesicles at boutons formed by sympathetic ganglion cells in tissue culture. These peptides were coupled to the DNA binding domain of the Drosophila transcription factor antennapedia, called penetratin. This facilitated the passage of peptides across the bouton membrane. FM1-43 was used to monitor the exocytosis of transmitter from depolarized boutons after their exposure to the penetratin-peptide sequences IETRHNEIIKLETSIRELHD of syntaxin and KGFLSSLFGGSSK of alpha-SNAP, both of which blocked secretion, whereas the peptide sequences SELDDRA-DALQAGASQFETSAAKLKRK of synaptobrevin did not. This report introduces a readily applicable method for determining the effect of different peptide sequences of vesicle-associated proteins on secretion at vertebrate boutons and presents an account of the effects of a selection of such peptides on exocytosis.

Apoptosis in cells of rat sympathetic ganglia during early ontogeny: electron microscopic study.

Postnatal ontogeny of sympathetic ganglia includes both proliferative processes and programmed cell death. Electron microscopy helps to evaluate the intensity and the relationship between these processes.

Reduced Rearing Temperature Augments Responses in Sympathetic Outflow to Brown Adipose Tissue

Sympathetic outflow to brown adipose tissue (BAT) contributes to both thermoregulation and energy expenditure in rats through regulation of BAT thermogenesis. Acute cold exposure in mature animals augments BAT thermogenesis; however, the enhanced BAT thermogenic response returns to normal shortly after cessation of the cold exposure. In this study, we sought to determine whether cold exposure in early neonatal life could induce enhanced responses in the sympathetic outflow to BAT and whether this altered sympathetic regulation would be sustained after the cold stimulus was removed. BAT sympathetic nerve activity (SNA) was recorded in urethane-chloralose-anesthetized, artificially ventilated rats that were raised from birth in either 18 or 30 degrees C environments and then, at 8 weeks of age, were maintained in 23 degrees C for at least 4 weeks. An acute hypothermic stimulus, disinhibition of a brainstem thermogenic network in the raphe pallidus, or electrical stimulation in this raphe site produced increases in BAT SNA that were twice as great in rats reared at 18 degrees C as in those reared at 30 degrees C. The norepinephrine content of the interscapular BAT (IBAT) and the number of sympathetic ganglion cells projecting to interscapular BAT were 70% greater in the 18 degrees C-reared rats. We conclude that neonatal exposure to a cold environment induces a permanent developmental alteration in the capacity for sympathetic stimulation of BAT thermogenesis that may be mediated, in part, by a greater number of sympathetic ganglion cells innervating BAT in cold-reared animals.

Functional triads consisting of ryanodine receptors, Ca(2+) channels, and Ca(2+)-activated K(+) channels in bullfrog sympathetic neurons. Plastic modulation of action potential.

Fluorescent ryanodine revealed the distribution of ryanodine receptors in the submembrane cytoplasm (less than a few micrometers) of cultured bullfrog sympathetic ganglion cells. Rises in cytosolic Ca(2+) ([Ca(2+)](i)) elicited by single or repetitive action potentials (APs) propagated at a high speed (150 microm/s) in constant amplitude and rate of rise in the cytoplasm bearing ryanodine receptors, and then in the slower, waning manner in the deeper region. Ryanodine (10 microM), a ryanodine receptor blocker (and/or a half opener), or thapsigargin (1-2 microM), a Ca(2+)-pump blocker, or omega-conotoxin GVIA (omega-CgTx, 1 microM), a N-type Ca(2+) channel blocker, blocked the fast propagation, but did not affect the slower spread. Ca(2+) entry thus triggered the regenerative activation of Ca(2+)-induced Ca(2+) release (CICR) in the submembrane region, followed by buffered Ca(2+) diffusion in the deeper cytoplasm. Computer simulation assuming Ca(2+) release in the submembrane region reproduced the Ca(2+) dynamics. Ryanodine or thapsigargin decreased the rate of spike repolarization of an AP to 80%, but not in the presence of iberiotoxin (IbTx, 100 nM), a BK-type Ca(2+)-activated K(+) channel blocker, or omega-CgTx, both of which decreased the rate to 50%. The spike repolarization rate and the amplitude of a single AP-induced rise in [Ca(2+)](i) gradually decreased to a plateau during repetition of APs at 50 Hz, but reduced less in the presence of ryanodine or thapsigargin. The amplitude of each of the [Ca(2+)](i) rise correlated well with the reduction in the IbTx-sensitive component of spike repolarization. The apamin-sensitive SK-type Ca(2+)-activated K(+) current, underlying the afterhyperpolarization of APs, increased during repetitive APs, decayed faster than the accompanying rise in [Ca(2+)](i), and was suppressed by CICR blockers. Thus, ryanodine receptors form a functional triad with N-type Ca(2+) channels and BK channels, and a loose coupling with SK channels in bullfrog sympathetic neurons, plastically modulating AP.

Potassium-channel closure taken to TASK

The resting potential of neurons and other excitable cells was a rather sacrosanct notion during the early years of intracellular recordings (1950–1970). It simply existed. In the Hodgkin and Huxley formalisms, it was represented by a fixed conductance; action potentials began from it and returned to it. Transmitters depolarized or hyperpolarized cells by opening distinct sets of channels that were selectively permeable to ions that had equilibrium potentials less negative (mixed cations) or more negative (chloride) than the resting potential. These became known as ligand-gated channels. It was also clear that some transmitters worked by opening K+-selective channels (particularly in the heart and in invertebrate neurons) but it was not obvious whether these were channels were already contributing to the resting potential, or whether an additional set of K+-selective channels were responsible. The idea that transmitters might work by closing K+ channels that were setting the resting potential was introduced by Weight and Votava 1 Weight F.F. Votava J. Slow synaptic excitation in sympathetic ganglion cells: evidence for synaptic inactivation of potassium conductance. Science. 1970; 170: 775-778 Crossref Scopus (115) Google Scholar , Nishi, and Kuba and Koketsu 2 Kuba K. Koketsu K. Synaptic events in sympathetic ganglia. Prog. Neurobiol. 1978; 11: 77-169 Crossref PubMed Scopus (131) Google Scholar as an explanation for the slow EPSP in sympathetic ganglion cells; at about the same time, Krnjevic and his colleagues 3 Krnjevic K. et al. The mechanism of excitation by acetylcholine in the cerebral cortex. J. Physiol. 1971; 215: 247-268 PubMed Google Scholar showed that such an action underlay the excitation of cortical neurons by ACh.

Early markers of neuronal differentiation in DRG: Islet-1 expression precedes that of Hu

The Hu and Islet-1 proteins are early markers of neuronal differentiation in the avian embryo. We here examine which of these markers is expressed first in avian dorsal root ganglia (DRG). Recently we showed that neural tube and DRG cells express Islet-1 after leaving the cell cycle, while sympathetic ganglion cells express Islet-1 while still dividing. Others have shown that Hu is found in cells that take up BrDU in the DRG, suggesting that it is expressed even earlier in the differentiation process than Islet-1. In this study we double-label sections for Hu and Islet-1 at several stages of embryonic development, using a simple antigen retrieval method in paraffin sections. At early stages many more cells are Islet-1 + than Hu +. In addition, although many cells express both markers, some Islet-1 +/Hu − cells are observed but the converse is never found. At later stages, almost all DRG neurons express both markers, although a few Islet-1 +/Hu − cells are still observed. Staining for Hu and Islet-1 at a later stage than previously reported shows that neither marker is expressed in DRG satellite cells. Our results suggest that Islet-1 is a useful marker for DRG neurons at earliest embryonic stages, and is likely to be expressed in DRG neurons before the Hu antigen.

Fatty acid synthase is expressed mainly in adult hormone-sensitive cells or cells with high lipid metabolism and in proliferating fetal cells.

Animal fatty acid synthase (FAS) is a homodimer protein which synthesizes long-chain fatty acids and is rich in liver, brain, breast, and lung. However, the precise cellular localization of FAS in human tissues has not been elucidated. Immunohistochemistry with a new antibody to human FAS revealed that in adult human tissues FAS is distributed mainly in cells with high lipid metabolism (adipocytes, corpus luteum, hepatocytes, sebaceous glands, and Type II alveolar cells), in hormone-sensitive cells (anterior pituitary, apocrine gland, breast, endometrium, prostate, seminal vesicle, and adrenal cortex), and in a subset of epithelial cells of duodenum and stomach, colon absorptive cells, cerebral neurons, basket cells of cerebellum, decidua, uroepithelium, and epidymis. In fetal cells at 20 weeks of gestation, FAS was mainly present in proliferative epithelial cells of the digestive and respiratory systems, proximal renal tubules, adrenocortical cells, and mesenchymal and hematolymphoid cells. Staining was significant in nonproliferating cells, as observed in adult, and in sympathetic ganglion cells, Leidig cells of testis, and Langhans cells of chorionic villi. FAS is maintained in hormone-sensitive cells and/or cells active in lipid metabolism in the adult and is expressed in proliferating cells in the fetus, suggesting active fatty acid synthesis for energy utilization or membrane lipids.

Avian transitin expression mirrors glial cell fate restrictions during neural crest development.

During development, trunk neural crest cells give rise to three primary classes of derivatives: glial cells, melanocytes, and neurons. As part of an effort to learn how neural crest diversification is regulated, we have produced monoclonal antibodies (MAbs) that recognize antigens expressed by neural crest cells early in development. One of these, MAb 7B3 (7B3), was found to recognize an avian transitin-like protein by co-immunostaining with a series of transitin-specific monoclonal antibodies and by Western blot analysis. In neural crest cell cultures, we found that 7B3 initially recognizes the majority of neural crest cells as they emerge from the neural tube. Subsequently, 7B3-immunoreactivity (IR) is progressively restricted to a smaller subpopulation of cells. In fully differentiated trunk neural crest cell cultures, 7B3-IR is expressed only by cells that do not express neuronal markers and lack melanin granules. During development in vivo, 7B3-IR is evident in neural crest cells on the medial, but not the lateral migration pathway, suggesting that it is not expressed by melanocyte precursors. Later, the antigen is detected in non-neuronal, presumptive glial cells in dorsal root ganglia (DRG) and sympathetic ganglia, as well as along ventral roots. Cultures of E5 DRG confirm that 7B3-IR is restricted to non-neuronal cells of ganglia, many of which closely associate with neuronal processes. Therefore, of the three major classes of differentiated trunk neural crest derivatives, 7B3 exclusively recognizes glial cells, including both satellite glia and Schwann cells. Since the pattern of 7B3 expression in vitro mirrors the pattern of glial cell fate-restrictions in the trunk neural crest lineage, and is expressed by neural crest-derived glia in vivo, we conclude that 7B3 is an early pan-glial marker for neural crest-derived glial cells and their precursors.

Modes of propagation of Ca2+-induced Ca2+ release in bullfrog sympathetic ganglion cells

How depolarization-induced Ca2+ entry or caffeine activates Ca2+-induced Ca2+ release (CICR) in the cytoplasm and nucleoplasm was studied by recording intracellular Ca2+ ([Ca2+]i) with a confocal microscope in cultured bullfrog sympathetic ganglion cells. The amplitude and propagation speed of voltage pulse-induced rises in [Ca2+]i were greater in the submembrane (< 5 μm depth) region than in the core region, and delayed and smaller, but significant, in the nucleus. Ryanodine and dantrolene reduced the rises in [Ca2+]i in both the cytoplasm and nucleus. A rapid application of high K+ solution induced global rises in [Ca2+]i in both the cytoplasm and nucleoplasm, which were decreased by dantrolene. Caffeine produced a slow, small rise in [Ca2+]i which grew into a global, regenerative rise both in the cytoplasm and nucleoplasm with some inward gradient in the cytoplasm. Each of the high [Ca2+]i phases during caffeine-induced [Ca2+]i oscillation began in the submembrane region, while low [Ca2+]i phases started in the core region. These results suggest that CICR activated by Ca2+ entry or caffeine occurs predominantly in the submembrane region causing an inwardly spreading Ca2+ wave or [Ca2+]i oscillations, and that the nuclear envelope can cause CICR in the nucleoplasm, which is delayed due to Ca2+ diffusion barrier at the nuclear pores.

Establishment and characterization of equine autonomic ganglion cell lines to enable direct testing of candidate toxins involved in equine dysautonomia (grass sickness).

To enable direct testing of a range of potential toxins or pathogens that might be involved in grass sickness, equine thoracic sympathetic chain ganglion cell lines were established from primary cell cultures by retroviral-mediated transduction of the temperature-sensitive mutant of the establishment oncogene encoding SV40 large T antigen. Morphological and behavioral features, temperature dependence, and immunocytochemical characteristics of the cell lines were investigated. The majority of cells were noradrenergic neurons in which dopamine-beta-hydroxylase, the enzyme that catalyzes norepinephrine synthesis, and neuropeptide Y coexisted. Cells treated with plasma from grass sickness cases that had previously been shown to induce autonomic nervous system damage when injected into normal horses showed significantly decreased mitochondrial function after 1 day. After 3 days exposure most cells showed severe degeneration in contrast to those treated with normal plasma. Liver and lung cell lines were also susceptible to plasma, suggesting that the toxin is not specifically neurotoxic.

Preferential formation of strong synapses during re-innervation of guinea-pig sympathetic ganglia.

1. Re-innervation of partially denervated sympathetic ganglion cells was investigated using intracellular recording in guinea-pig lumbar paravertebral ganglia in vitro. The question addressed was whether the pattern of innervation by strong (suprathreshold) and weak (subthreshold) inputs seen normally was restored during re-innervation. 2. L5 ganglion cells each normally received 3.9 +/- 0.2 preganglionic inputs of which 1.2 +/- 0.1 were strong. Only 0.9 +/- 0.1 inputs arose from the L4 segment, the last of the thoracolumbar outflow, and only 11 % of these were strong. 3. Three to five weeks after cutting the sympathetic chain above the L4 white ramus, each neurone received 2.1 +/- 0.1 inputs after sprouting of surviving axons. Nearly 60 % of neurones received a strong input and the normal ratio of weakstrong synapses was restored. 4. Total charge transfer evoked by L4 inputs increased from 8.8 +/- 1.4 to 27. 6 +/- 2.4 pC per neurone after re-innervation, reaching 77 % of that in normal ganglia. This was primarily due to the formation of new strong inputs of normal size. 5. The synaptic events at the new strong synapses and the types of Ca2+ channel mediating transmitter release (N-type and channels resistant to specific antagonists) were the same as those at control strong synapses. 6. The data indicate that, following partial denervation, sprouting of surviving preganglionic axons results in the preferential formation of strong synapses with the same characteristics as those in normal ganglia. Thus the pattern of functional transmission by a single strong input to each cell was restored rather than the recovery of the number of synaptic connections.

The autonomic nerve supply of male sex organs – an important target of circulating androgens

The autonomic nervous system plays a critical role in the regulation of smooth muscle contraction, exocrine secretion and blood flow in the male reproductive organs. Many of the autonomic neurons that supply these targets lie in the pelvic ganglia, which contain both sympathetic and parasympathetic ganglion cells. In rats, removal of circulating androgens by castration before or after puberty has profound effects on the structure, chemistry and function of particular classes of pelvic autonomic neurons. While most of these effects occur in reproductive pathways, some bladder- or bowel-projecting neurons also exhibit androgen-sensitivity. Our studies on these ganglion cells and their spinal preganglionic inputs show that testosterone (or a metabolite) has potent actions both before and after puberty and can be considered essential for the normal maturation and maintenance of some pelvic autonomic reflex pathways. Androgen receptors are distributed widely throughout various components of these circuits, suggesting that testosterone may have direct effects on neuronal gene expression. Together, the studies show that in addition to powerful effects on some central neurons controlling reproductive behaviour, testosterone has similarly important effects on peripheral neurons that trigger and complete copulatory reflexes.

Two Types of K+Channel Subunit, Erg1 and KCNQ2/3, Contribute to the M-Like Current in a Mammalian Neuronal Cell

The potassium M current was originally identified in sympathetic ganglion cells, and analogous currents have been reported in some central neurons and also in some neural cell lines. It has recently been suggested that the M channel in sympathetic neurons comprises a heteromultimer of KCNQ2 and KCNQ3 (Wang et al., 1998) but it is unclear whether all other M-like currents are generated by these channels. Here we report that the M-like current previously described in NG108-15 mouse neuroblastoma x rat glioma cells has two components, "fast" and "slow", that may be differentiated kinetically and pharmacologically. We provide evidence from PCR analysis and expression studies to indicate that these two components are mediated by two distinct molecular species of K(+) channel: the fast component resembles that in sympathetic ganglia and is probably carried by KCNQ2/3 channels, whereas the slow component appears to be carried by merg1a channels. Thus, the channels generating M-like currents in different cells may be heterogeneous in molecular composition.

Differential expression of Islet-1 in neural crest-derived ganglia: Islet-1+ dorsal root ganglion cells are post-mitotic and Islet-1+ sympathetic ganglion cells are still cycling

The Islet-1 antigen is an early marker of differentiation of neural tube cells, and is expressed in many other embryonic cells as well. It had been reported that Islet-1 is expressed only in post-mitotic sympathetic neuroblasts in vitro, unlike other differentiation markers. We have double-labeled St. 23 chick embryos for bromodeoxyuridine (BrDU) and Islet-1 and found that neural tube and dorsal root ganglion (DRG) cells express Islet-1 after leaving the cell cycle, while sympathetic ganglion (SG) cells express Islet-1 while still dividing.

Analysis of hyposmolarity-induced taurine efflux pathways in the bullfrog sympathetic ganglia

Hyposmolarity-induced taurine release was dependent on the decrease in medium osmolarity (5–50%) in the satellite glial cells of the bullfrog sympathetic ganglia. Release of GABA induced by hyposmolarity was much less than that of taurine. Omission of external Cl − replaced with gluconate totally suppressed taurine release, but only slightly suppressed GABA release. Bumetanide and furosemide, blockers of the Na +/K +/2Cl − cotransport system, inhibited taurine release by about 40%. Removal of external Na + by replacement with choline, or omission of K +, suppressed taurine release by 40%. Antagonists of the Cl −/HCO − 3 exchange system, SITS, DIDS and niflumic acid, significantly reduced taurine release. The carbonic anhydrase inhibitor, acetazolamide, reduced the taurine release by 34%. Omission of external HCO − 3 by replacement with HEPES caused a 40% increase in the hyposmolarity-induced taurine release. Hyposmolarity-induced GABA release was not affected by bumetanide or SITS. Chloride channel blockers, 5-nitro-2-(3-phenylpropylamino) benzoic acid (NPPB) and N-phenylanthranilic acid (DPC), practically abolished taurine release. Blockers of K + channels, clofilium and quinidine, had no effect on the taurine release. The hyposmolarity-induced taurine release was considerably enhanced by a simultaneous increase in external K +. GABA was not mediated by the same transport pathway as that of taurine. These results indicate that Cl − channels may be responsible for the hyposmolarity-induced taurine release, and that Na +/K +/2Cl − cotransporter and Cl −/HCO − 3 exchanger may contribute to maintain the intracellular Cl − levels higher than those predicted for a passive thermodynamic distribution in the hyposmolarity-induced taurine release.

2'-Deoxyadenosine causes cell death in embryonic chicken sympathetic ganglia and brain.

Previous work has shown that nucleosides produce apoptosis in sympathetic ganglion (SG) cells in vitro. The present study examined the effects of nucleosides on the development of the chick embryo in vivo with special attention to the SG and the optic tectum of the central nervous system. In the presence of an adenosine deaminase inhibitor, adenosine and 2'-deoxyadenosine (2'-dAdo) produced different toxicity patterns: both adenosine and 2'-dAdo were toxic to E3 embryos, but only 2'-dAdo was toxic at later stages (E6 1/2, E11). Dosage experiments on E6 1/2 embryos showed that adenosine was less toxic than 2'-dAdo and that 2'-dAdo in sublethal doses was teratogenic. We also examined the effects of 2'-dAdo on embryonic chicken SG and optic tectum in vivo to determine whether sublethal doses of 2'-dAdo produced cell death in these centers on E6 1/2 and 10. In the E6 1/2 SG, 2'-dAdo produced significant neuron loss (83%) and a decrease in SG volume (65%); however, at E10, there was only minor cell loss (7%) and no significant change in SG volume. In the optic tectum at E6 1/2, cell loss was confined mainly to the tectal ventricular zone, but there was little sign of cell loss in this organ at E10. Since cell production is vigorous in the SG and optic tectum at E6 1/2 but relatively low at E10, 2'-dAdo appears to work by stopping cell proliferation. The ineffectiveness of 2'-dAdo at E10 may result from the lethality of 2'-dAdo to the embryo at low concentrations (30 microM) in vivo, well below the apoptosis-inducing concentrations employed in vitro (100-300 microM). These data extend previous findings showing that purine and pyrimidine metabolism plays an important role in development.

Neuronal nuclear antigen (NeuN): a marker of neuronal maturation in early human fetal nervous system.

Neuronal nuclear antigen (NeuN) immunocytochemistry was studied in 15 normal human fetal nervous systems of 8-24 weeks gestation and in four term neonates. Material was derived from products of conception or from autopsy. Antigen retrieval was enhanced for immunocytochemistry by microwave heating of formalin-fixed paraffin sections. NeuN appears highly specific as a marker of neuronal nuclei in human fetal brain. Only rare nuclei are recognized in the germinal matrix. Cerebellar external granule cells are more strongly immunoreactive than postmigratory internal granule cells until 24 weeks gestation; by term most internal and only a few external granule cells are recognized by NeuN antibody. In the cerebrum, some reactive nuclei are demonstrated along radial glial fibers, particularly near the cortical plate. Within the cortical plate, only deep neurons (future layers 4-6) are marked at 19-22 weeks, but by 24 weeks most neurons in the cortical plate exhibit immunoreactivity, though at term some in layer 2 are still non-reactive. Some neurons fail to be recognized by NeuN at all ages: Cajal-Retzius cells, Purkinje cells, inferior olivary and dentate nucleus neurons, and sympathetic ganglion cells are examples. Despite their common origin in the cerebellar tubercle, basal pontine neurons are strongly reactive even before midgestation, hence NeuN does not predict embryonic origin. Neurons of dorsal root and cranial nerve ganglia are reactive even at 8 weeks. This study of normal fetal central nervous system provides a basis for neuropathological evaluation and as a prelude to applications in cerebral dysgeneses.