Dopamine1 receptor agonists reverse opioid respiratory network depression, increase CO2 reactivity

In adult pentobarbital-anesthetized and unanesthetized decerebrate cats, the D(1)R agonists (6-chloro-APB, SKF-38393, dihydrexidine) given intravenously restored phrenic nerve and vagus nerve respiratory discharges and firing of bulbar post-inspiratory neurons after the discharges were abolished by the micro-opioid receptor agonist fentanyl given intravenously. Reversal of opioid-mediated discharge depression was prevented by the D(1)R antagonist SCH23390. Iontophoresis of the micro-opioid receptor agonist DAMGO depressed firing of medullary bulbospinal inspiratory neurons. Co-iontophoresis of SKF-38393 did not restore firing and had no effect on bulbospinal inspiratory neuron discharges when applied alone. The D(1)R agonists given intravenously prolonged and intensified phrenic nerve and bulbospinal inspiratory neuron discharges. They also increased reactivity to CO(2) by lowering the phrenic nerve apnea threshold and shifting the phrenic nerve-CO(2) response curve to lower et(CO(2)) levels. Intravenous fentanyl on the other hand decreased CO(2) reactivity by shifting the phrenic nerve apnea threshold and the response curve to higher et(CO(2)) levels. Fentanyl effects on reactivity were partially reversed by D(1)R agonists.     

Expression of BRI,the normal precursor of the amyloid protein of familial British dementia,in human brain

Familial British dementia (FBD) is characterized neuropathologically by deposition of a unique amyloid-forming protein, ABri. It is a fragment of an abnormal form of a precursor protein, BRI. In FBD, BRI is elongated by 11 amino acids due to a point mutation that prevents recognition of the normal stop codon. We have investigated the expression of normal BRI in non-FBD cases. Three antibodies were raised against sequences of BRI and were used for immunoblotting and immunohistochemistry. Each of these antibodies detected a band at approximately 35 kDa by Western blotting. In postmortem human brain tissues, BRI was detected as fine granules in the neuronal cytoplasm. Pyramidal neurons in CA3 and CA4 of the hippocampus as well as Purkinje cells in the cerebellar cortex were most intensely stained for BRI. Such a distribution of neurons strongly expressing BRI parallels the reported occurrence of ABri deposits in patients with FBD. In pathological cases, BRI was detected in dystrophic neurites in senile plaques, around lesions in ischemic cases, in torpedo and glumose changes in the cerebellum, Lewy neurites, ballooned neurons, and neurons generally in hypoxic cases. These results suggest that BRI is transported in neuronal processes and is possibly involved in some role in nerve terminals. While a physiological role of BRI in brain remains to be determined, the behavior of BRI in diverse brain lesions appears to be somewhat analogous to that of amyloid precursor protein, which is the source of the -amyloid protein of Alzheimers disease.     

Characterisation of tectal ephrin-A2 expression during optic nerve regeneration in goldfish: implications for restoration of topography

EphA receptors and their ligands the ephrin-As, expressed as retinal and tectal gradients, are required for the development of retino-tectal topography [Neuron 25 (2000) 563] and its restoration during goldfish optic nerve regeneration [Mol. Cell. Neurosci. 25 (2004) 56]. We have reported previously that, during regeneration, a transient EphA3/A5 gradient is formed by differential expression across the entire retinal ganglion cell (RGC) population [Neurosci. Abs. 33 (2003) 358.2; Exp. Neurol. 183 (2003) 593]. In retino-recipient tectal layers, ephrin-A2 is normally expressed by only a sub-population of cells, but during regeneration, there is a graded increase with more expressing cells caudally than rostrally [Exp. Neurol. 166 (2000) 196]. Here, we examine the characteristics of tectal ephrin-A2 expression during regeneration. We report that the level of ephrin-A2 expression is comparable for all ephrin-A2-positive cells in normal animals and during regeneration. Using double-labelling immunohistochemistry for ephrin-A2 and specific cell markers (NeuN for neurons, GA5 for astrocytes, NN-1 for microglia/endothelial cells and 6D2 for oligodendrocytes), we demonstrate that ephrin-A2-expressing cells, as in normal animals, are exclusively neuronal. Moreover, double labelling with BrdU showed that ephrin-A2 is expressed in resident cells and not those generated during optic nerve regeneration [Brain Res. 854 (2000) 178, 153 (1978) 345].     

Differential modulation of apoptosis-associated proteins by ethanol in rat cerebral cortex and cerebellum

Chronic ethanol treatment caused a differential modulation of apoptosis-associated proteins, cytochrome c release, concomitant with procaspase-9 and procaspase-3 activation leading to oligonucleosomal DNA fragmentation in rat cerebral cortex and cerebellum. Caspase-3 proform (32 kDa) showed decreased immunoreactivity in cortex and cerebellum, while the cleaved active fragment (17 kDa) increased significantly in cerebellum after ethanol treatment. Further, chronic ethanol treatment increased caspase-3 activity in cortex and to a higher extent in cerebellum, which was further confirmed by blocking experiments with caspase-3 specific inhibitor, N-acetyl-Asp-Glu-Val-Asp-aldehyde (Ac-DEVD-CHO). We tested whether activated caspase-3 cleaves downstream substrates such as poly (ADP-ribose) polymerase-1 and protein kinase C-delta (PKC-δ). Western blots showed poly (ADP-ribose) polymerase-1 cleavage to its signature fragment of 85 kDa and decreased levels of PKC-δ in cerebral cortex and cerebellum after ethanol treatment, suggestive of caspase-3 activation. Elevated caspase-3 activity in cerebellum than cortex correlating with cytochrome c, caspase-9, active caspase-3 (p17), poly (ADP-ribose) polymerase-1 and PKC-δ data, suggests a mechanism by which ethanol might be exerting pro-apoptotic events in brain and how selective brain regions such as cerebellum are vulnerable to ethanol neurotoxicity in terms of cell death.     

Signal transduction and neurosurvival in experimental models of brain injury

Brain injury and neurodegenerative disease are linked by their primary pathological consequence-death of neurons. Current approaches for the treatment of neurodegeneration are limited. In this review, we discuss animal models of human brain injury and molecular biological data that have been obtained from their analysis. In particular, signal transduction pathways that are associated with neurosurvival following injury to the brain are presented and discussed.     

Pim1在体外培养大脑皮层神经元氧糖剥夺/复氧损伤中的表达及作用

目的 探讨原代培养大脑皮层神经元缺氧缺血损伤后Pim1的表达及其对细胞凋亡的作用。方法 取新生1日龄C57BL/6小鼠的大脑皮层神经元进行原代培养，培养第8天更换无糖无血清DMEM培养基，于1% O₂条件下培养3 h后，换为正常条件下培养，即氧糖剥夺/复氧（OGD/R）处理，以模拟体内神经元缺氧缺血状态。分别于OGD/R后0、6、12、24 h收集细胞，同时设立神经元正常培养组。原代培养神经元中分别转染Pim1过表达质粒或空质粒，然后分别进行正常培养或OGD/R处理，分别命名为Pim1组、对照组、OGD/R组和OGD/R+Pim1组；采用Real-time PCR检测Pim1 mRNA的表达，采用Western blot检测Pim1蛋白和凋亡相关蛋白活化的半胱氨酸蛋白酶（CC3）的表达。采用TUNEL法检测细胞凋亡。结果 Real-time PCR和Western blot结果显示，与正常组相比，OGD/R后神经元中Pim1 mRNA及其蛋白表达均显著降低，且均从OGD/R后0 h开始下降，12 h最低，24 h回升但仍维持在较低水平（P < 0.05）。Pim1过表达转染使神经元中Pim1蛋白水平增加。Pim1+OGD/R组CC3表达水平明显低于OGD/R组，Pim1+OGD/R组细胞凋亡率也较OGD/R组显著减少（P < 0.01）。结论 缺氧缺血损伤引起体外培养神经元中Pim1表达下降。过表达的Pim1可以抑制OGD/R诱导的神经元凋亡。     

大鼠肱肌肌支的脊髓神经根定位

目的 比较逆行示踪法及肌电图检测法在定位肱肌肌支及肱肌脊髓神经根起源中的价值,并探讨将肌电图检测法运用于定位人类肌皮神经肱肌肌支脊髓神经根起源的可能性.方法 在大鼠臂丛神经根切断-保留模型中运用神经元逆行示踪法定位肱肌肌支及肱肌的脊髓神经根起源;通过分析刺激大鼠各臂丛神经根时肱肌记录到的CMAP指标定位肱肌肌支及肱肌的脊髓神经根起源.结果 大鼠桡神经肱肌肌支的运动纤维主要来源于C7神经根,大鼠肌皮神经肱肌肌支的运动纤维主要来源于C5、6神经根;在定位大鼠肱肌的脊髓神经根起源时,肌电图法与逆行示踪法的检测结果基本一致.结论 通过分析逆行示踪和肌电图检测的结果,能够精确定位大鼠特定神经、肌肉的脊髓神经根来源;在临床研究中,肌电图检测法可以用于定位人类肌皮神经肱肌肌支的脊髓神经根起源.     

脑血管内皮细胞与神经系统变性病关系的研究进展

长期以来，对神经系统疾病的认识和研究都局限在神经元损伤和修复等方面，但近来研究显示，脑微血管内皮细胞（BMEC）、神经系统中非神经元细胞等在神经系统疾病的发生和发展中起到了相当重要的作用。本文基于近期血脑屏障（BBB）和神经血管单元等相关新概念的提出和完善，就BMEC与神经系统变性疾病关系的研究进展作一综述。     

A monoclonal antibody 5E5 recognizes an intranuclear antigen selectively present in a subpopulation of the neurons

Monoclonal antibody 5E5 labeled the nuclear antigen of the neurons in the guinea pig and rat central nervous systems including the cerebrum, cerebellum, spinal cord and retina. This antibody could discriminate neurons even among the same cell class. In in vitro study, only 10% of dividing PC12 cells was labeled with this antibody. An electron microscopic immunohistochemical study also revealed that this antibody selectively labeled heterochromatins in the neurons. Although we could not obtain any positive result by an immunoblot study, the antigenecity was remarkably diminished by the DNase I or S1 Nuclease treatment on the tissue sections whereas RNase and trypsin was ineffective. These results suggested that this antigen might be a single-stranded DNA-protein complex resistant to proteolytic procedures, and possibly related to cell function or state of differentiation.