Postnatal phenotype and localization of spinal cord V1 derived interneurons

Developmental studies identified four classes (V0, V1, V2, V3) of embryonic interneurons in the ventral spinal cord. Very little is known, however, about their adult phenotypes. Therefore, we characterized the location, neurotransmitter phenotype, calcium-buffering protein expression, and axon distributions of V1-derived neurons in the adult mouse spinal cord. In the mature (P20 and older) spinal cord, most V1-derived neurons are located in lateral LVII and in LIX, few in medial LVII, and none in LVIII. Approximately 40% express calbindin and/or parvalbumin, while few express calretinin. Of seven groups of ventral interneurons identified according to calcium-buffering protein expression, two groups (1 and 4) correspond with V1-derived neurons. Group 1 are Renshaw cells and intensely express calbindin and coexpress parvalbumin and calretinin. They represent 9% of the V1 population. Group 4 express only parvalbumin and represent 27% of V1-derived neurons. V1-derived Group 4 neurons receive contacts from primary sensory afferents and are therefore proprioceptive interneurons. The most ventral neurons in this group receive convergent calbindin-IR Renshaw cell inputs. This subgroup resembles Ia inhibitory interneurons (IaINs) and represents 13% of V1-derived neurons. Adult V1-interneuron axons target LIX and LVII and some enter the deep dorsal horn. V1 axons do not cross the midline. V1-derived axonal varicosities were mostly (>80%) glycinergic and a third were GABAergic. None were glutamatergic or cholinergic. In summary, V1 interneurons develop into ipsilaterally projecting, inhibitory interneurons that include Renshaw cells, Ia inhibitory interneurons, and other unidentified proprioceptive interneurons.     

Cyto- and chemoarchitecture of the cerebral cortex of an echidna (Tachyglossus aculeatus). II. Laminar organization and synaptic density

We have examined the distribution and morphology of neurons immunoreactive for nonphosphorylated neurofilament protein (SMI-32 antibody), calcium-binding proteins (parvalbumin, calbindin, calretinin), and neuropeptide Y as well as neurons reactive for NADPH diaphorase in the cerebral cortex of the Australian short-beaked echidna (Tachyglossus aculeatus). We have also studied synaptic morphology and density in S1 somatosensory cortex and assessed parameters associated with metabolic activity of the cerebral cortex (vessel volume density, mitochondrial volume density, and mitochondrial numerical density) in semi- and ultrathin sections. SMI-32 immunoreactivity was found mostly in layer V pyramidal neurons in selected cortical regions (S1, PV, V1, A). These neurons often showed atypical morphology compared with therian cortex. Neurons immunoreactive for calcium-binding proteins were broadly similar in both morphology and distribution to those seen in therian cortex, although calretinin-immunoreactive neurons were rare. Both Gray type I and Gray type II synapses could be identified in echidna S1 cortex and were similar to those seen in therian cortex. Peak synaptic density was in upper layer IV, followed by layer I, lower layer II, and upper layer III. Most synapses were of type I (72%), although types I and II were encountered with similar frequency in lower layer II and upper layer III. The capillary volume fraction values obtained for the echidna (from 1.18% in V1 to 1.34% in S1 cortex) fall within the values for rodent cortex. Similarly, values for mitochondrial volume fraction in echidna somatosensory cortex (4.68% +/- 1.76%) were comparable to those in eutherian cortex.     

Role of the Otx1 gene in cell differentiation of mammalian cortex

This study analyses by immunohistochemical methods the effects of the deletion of the Otx1 gene on 12 areas of the cerebral cortex and on neurons expressing Ca-binding proteins (CaBP), such as parvalbumin (Pv) and calbindin-D28K (Cb). We found that the deletion of the Otx1 gene modified differently the various cortical areas. The decrease in cortical thickness ranged from 29.35 to 9.85% and the reduction in cellular population from 35.90 to 3.65% in the different cortical areas. The influence of the Otx1 gene concerns all cortical layers with variable effects on different cortical areas. The cellular population of cerebral cortex considered as a whole was reduced by 20.67%, Pv-positive (Pv+) cells by 58.01% and Cb-positive (Cb+) cells by 51.54%. The quantitative distribution of Pv+ and Cb+ cells varied independently in the different cortical areas. Topographic analysis of CaBP cells in Otx1-null mice (Otx1(-/-)) showed that Pv+ cells were principally distributed in layers IV and V and Cb+ cells in layers V and VI. Given that in the development of wild-type mice both cell types first appear in deep layers and later spread to superficial ones, the segregation of CaBP neurons in inner layers of Otx1(-/-) animals is an index of the immaturity of the cerebral cortex of these animals. This study showed that the Otx1 gene has a more complex role than previously reported, as it is involved in the maturation and differentiation of various cerebral cortices, and, specifically, in the development of CaBP cells.     

AII amacrine cells in the mammalian retina show disabled-1 immunoreactivity

Disabled 1 (Dab1) is an adapter molecule in a signaling pathway, stimulated by Reelin, which controls cell positioning in the developing brain. It has been localized to AII amacrine cells in the mouse and guinea pig retinas. This study was conducted to identify whether Dab1 is commonly localized to AII amacrine cells in the retinas of other mammals. We investigated Dab1-labeled cells in human, rat, rabbit, and cat retinas in detail by immunocytochemistry with antisera against Dab1. Dab1 immunoreactivity was found in certain populations of amacrine cells, with lobular appendages in the outer half of the inner plexiform layer (IPL) and a bushy, smooth dendritic tree in the inner half of the IPL. Double-labeling experiments demonstrated that all Dab1-immunoreactive amacrine cells were immunoreactive to antisera against calretinin or parvalbumin (i.e., other markers for AII amacrine cells in the mammalian retina) and that they made contacts with the axon terminals of the rod bipolar cells in the IPL close to the ganglion cell layer. Furthermore, all Dab1-labeled amacrine cells showed glycine transporter-1 immunoreactivity, indicating that they are glycinergic. The peak density was relatively high in the human and rat retinas, moderate in the cat retina, and low in the rabbit retina. Together, these morphological and histochemical observations clearly indicate that Dab1 is commonly localized to AII amacrine cells and that antiserum against Dab1 is a reliable and specific marker for AII amacrine cells of diverse mammals.     

Distinct expression of phosphorylated N-methyl-D-aspartate receptor NR1 subunits by projection neurons and interneurons in the striatum of normal and amphetamine-treated rats

N-methyl-D-aspartate (NMDA) receptors are heteromeric assemblies of subunits (NR1 and NR2A-D), and are enriched in the striatum. Receptor phosphorylation has recently been demonstrated on the NR1 subunit at three serine residues, 897, 896, and 890, which appear to correspond to the level of receptor activity. In this study, expression of phospho-specific NR1 subunits at serine 897 (pNR1S897), serine 896 (pNR1S896), or serine 890 (pNR1S890) in neurochemically identified neurons of the adult rat striatum was detected by using double-immunofluorescent labeling or combined in situ hybridization and immunohistochemistry. In both the dorsal and ventral striatum, pNR1S897 was expressed at high levels in projection neurons containing >55% dynorphin (striatonigral) and >90% enkephalin (striatopallidal) and in interneurons that were 100% positive for choline, >90% positive for parvalbumin, and >45% positive for somatostatin (co-containing neuropeptide Y and neuronal nitric oxide synthase). Low levels of pNR1S896 were present in a small portion of projection neurons (<15% for both populations of projection neurons) and were almost lacking in the three types of interneurons. Interestingly, pNR1S890 was exclusively expressed in most parvalbumin-containing interneurons (70-80%). Acute administration of a psychostimulant, amphetamine, increased the number of dynorphin-containing projection neurons and parvalbumin interneurons showing detectable levels of pNR1S896 and pNR1S890, respectively. These results demonstrate the distinct expression of phospho-NR1 subunits in different populations of striatal projection neurons and interneurons at variable levels in normal rats; they also demonstrate that phosphorylation of NR1, at least on serine 896 and 890 sites, is sensitive to drug exposure.     

Deafferentation-induced abnormal neurofilament phosphorylation in red nucleus neurones

Hippocampal deafferentation has been proposed as a pathogenetic mechanism for neurofibrillary tangle (NFT) formation in human mesolimbocortical dementia. We previously developed a rodent model of hippocampal deafferentation involving bilateral destructive lesions of the ventrotegmental area (VTA), septum of the medial forebrain and entorhinal cortex combined with pharmacological inhibition of serotonin 5-HT2 and dopamine D1 receptors. Unexpectedly, we observed an alteration in phosphorylated neurofilament protein immunoreactivity and argyrophilia in magnocellular neurones of the red nucleus. Here, we determined the neuroanatomical, pharmacological and temporal requirements for this effect on red nucleus neurones. We found that abnormal phosphorylation and argyrophilia were critically dependent on bilateral destruction of the VTA and antagonism of 5-HT2 receptors. Although extensive neurofilament hyperphosphorylation and argyrophilia were observed in red nucleus magnocellular neurones within nine days of treatment, no NFTs were formed and these effects were transitory. Resolution of these cytoskeletal abnormalities was accompanied by increased expression of the calcium binding protein, parvalbumin, suggesting that alterations in intraneuronal calcium levels may modify the deafferentation response.     

大鼠三叉神经脊束核尾侧亚核Ⅱ层内CB样,PV样阳性结构的分布及？…

本研究用免疫组织化学方法观察了Ｃａｌｂｉｎｄｉｎ Ｄ－２８ｋ（ＣＢ）样和Ｐａｒｖａｌｂｕｍｉｎ（ＰＶ）样胞体、纤维和终末在三叉神经脊束核尾侧亚核（Ｖｃ）Ⅱ层内的公布及它们的突触联系。在光镜下观察到ＣＢ样和ＰＶ样阳性胞体、纤维和终末在ＩＩ层内侧带（ＩＩｉ）最为密集，ＰＶ样阳性神经元的胞体稍大，但数量少于ＣＢ样阳性神经元。在电镜下观察到ＣＢ样或ＰＶ样阳性结构主要形成下列４种突触联系：⑴阳性轴突终末与阳     

Glutamic-acid-decarboxylase-and parvalbumin-like-immunoreactive structures in the olfactory bulb of the human adult

This study examines the distribution and morphological characteristics of glutamic-acid-decarboxylase-like (GAD)- and parvalbumin-like (PA)-immunoreactive structures in the olfactory bulb of the human adult. GAD-immunoreactive somata occurred in the glomerular layer, the external granule cell layer, the more superficial portion of the external plexiform layer, and the internal granule cell layer. The cells were small- to medium-sized. Demonstration of lipofuscin pigment revealed the presence of unpigmented as well as pigmented neurons, thus suggesting the existence of two subpopulations of GAD-positive neurons. GAD-immunoreactive puncta and/or fibers were mainly seen in the periglomerular region and the internal granule cell layer. All other layers of the bulb, as well as the intrabulbar portion of the anterior olfactory nucleus, displayed considerably less of these puncta and/or fibers. The olfactory nerve layer remained practically clear of immunoreactive material. PA-immunoreactive somata occurred in the glomerular layer and both the external and internal granule cell layer. Only a small number of immunoreactive nerve cells were encountered within the white matter or the olfactory tract. Most PA-positive neurons displayed characteristics of short axon cells whereas a few others resembled van Gehuchten cells. All of the PA-immunoreactive neurons were devoid of lipofuscin pigment. Immunoreactive puncta and fibers were present in all layers though predominating in the periglomerular region, the olfactory nerve layer, and the internal granule cell layer. The intrabulbar portions of the anterior olfactory nucleus did not show any immunoreactive structures.     

大鼠脑干内三叉神经本体觉中枢通路中小白蛋白样阳性神经元的分布与发育

应用免疫组织化学技术对脑干内三叉神经本体觉中枢通路中PV样阳性神经元的分布与发育进行了观察.结果发现:①早在胚胎13 d时,首先在三叉神经中脑核(Vme)内观察到许多含小白蛋白(Parvalbumin,PV)样阳性神经元,主要为大的假单极神经元,呈中等阳性反应.②生后3 d时,Vme内PV样阳性神经元的数量明显增多,免疫反应呈强阳性,并可观察到Probst束呈强阳性反应.③生后10 d时,在三叉神经脊束核吻侧亚核背内侧部(Vodm)及三叉神经感觉主核背内侧部(Vpdm)均出现少量中等强度的PV样阳性神经元.④生后14 d时,三叉神经脊束核吻侧亚核邻接的外侧网状结构(LRF),三叉上核尾外侧部(Vsup-CL),三叉神经运动核腹侧区(AVM)及上橄榄核背侧区(ADO)均出现PV样阳性神经元.⑤生后21 d时,Vodm和LRF(Vodm-LRF)区、"带状区"包括Vpdm,Vsup-CL,ADO,AVM及Probst束内的PV样阳性神经元及纤维的分布均达成年大鼠水平.上述结果表明,大鼠脑干内三叉神经本体觉中枢通路中PV样阳性神经元的分布、发育以及PV样阳性纤维的形成可能与胚胎及生后发育期该通路中神经元的功能成熟有关.