Second-generation antipsychotic drugs, olanzapine, quetiapine, and clozapine enhance neurite outgrowth in PC12 cells via P13K/AKT, ERK, and pertussis toxin-sensitive pathways

Second-generation antipsychotic drugs, olanzapine, quetiapine, and clozapine, were found to enhance neurite outgrowth induced by nerve growth factor (NGF) in PC12 cells. These drugs increased the number of cells bearing neurites, the length of primary neurites, and the size of the cell body of NGF-differentiated PC12 cells. In addition, the drugs induced sprouting of neurite-like processes in PC12 cells in the absence of NGF. Olanzapine, quetiapine, and clozapine enhanced the phosphorylation of Akt and ERK in combination with NGF, and specific inhibitors of these pathways attenuated these effects. Pretreatment of cells overnight with pertussis toxin had no effect on NGF-induced differentiation but significantly decreased the effects of the antipsychotic drugs on neurite outgrowth, suggesting that G_i/G_o-coupled receptors are involved in the response to drug. A better understanding of the mechanisms underlying the effects of the second-generation drugs might suggest new therapeutic targets for enhancement of neurite outgrowth.     

Effects of calcium ion on neurite outgrowth of rat spinal cord neurons in vitro: The role of non-neuronal cells in regulating neurite sprouting

The interactions of nerve cells with their environment and other cells are specific to different stages of cellular differentiation. Neurite outgrowth was measured from cultured spinal cord neurons under the influence of different Ca²⁺ concentrations. We used fluorodeoxyuridine (FuDr), an antimitotic agent which reduces significantly the proportion of non-neuronal cells in spinal cord cell cultures, to examine the effects of non-neuronal cells on neurite outgrowth. Spinal cord neurons responded to changes in their environment by means of two types of neurite outgrowth: sprouting and elongation. The concurrent presence of non-neuronal cells led to increased sprouting of neurites in certain ionic environments, thus lending support to the idea that non-neuronal cells release diffusible factors which influence sprouting and guide neurite outgrowth.     

Dopamine and serotonin inhibition of neurite elongation of different identified neurons

This study demonstrates that a second classical neurotransmitter, dopamine, can act to suppress regenerative neurite outgrowth. Single identified neurons were dissected from two central ganglia of the snail Helisoma, and growth cone motility was studied as neurites regenerated in cell culture. Both dopamine and serotonin inhibited growth cone motility and elongation of neurites. Outgrowth inhibition ranged from sustained arrest to a similar but transient response. The effects of dopamine and serotonin are neuron-selective. Specific neurons affected by dopamine and serotonin represent distinct sets. One neuron was found that responds to both agents. The implications of neurotransmitter regulation of the dynamics of neuronal morphology are discussed.     

Functional identification of integrin laminin receptors that mediate process outgrowth by human SY5Y neuroblastoma cells

Treatment of the human neuroblastoma cell line SY5Y with nerve growth factor (NGF) induces terminal neuronal differentiation of a subpopulation of cells which can be selected by treatment with a DNA synthesis inhibitor. We have examined the interactions of navie (untreated) and NGF-differentiated SY5Y cells with laminin, and identifid integrin receptors that mediate laminin-induced process outgrowth. Differentiated cells displayed a greater capacity for process extension, which correlated with increased expression of integrin laminin receptors. Both naive and differentiated cells expressed integrins α1/β1, α2/β1, and α3/β1 but the differentiated population expressed about 5-fold higher levels of α1/β1 and about 2-fold nore α2/β1 and α3/β1 on their surface. Function blocking monoclonal antibodies were used to identify integrin receptors mediating process outgrowth. The anti-α1 monoclonal antibodies were used to identify intergrin receptors mediating process outgrowth. The anti-α1 moniclonal antibody SR84 was shown to block α1 function and inhibit process outgrowth on laminin. Despite the presence of multiple integrins which have been shown to bind laminin in other cell types, α1/β1 mediated the majority of process outgrowth in both naive and differentiated cells, with a minor role played by α3/β1. These data indicate that α1/β1 function is requried for process outgrowth on laminin by SY5Y cells and suggest that increased expression may be a crucial aspect of neuronal differentiation. © 1994 Wiley-Liss, Inc.     

Inhibition of PC12 Cell Attachment and Neurite Outgrowth by Detergent Solubilized CNS Myelin Proteins

Adhesion and neurite outgrowth of PC12 cells, as well as the spreading of 3T3 fibroblasts, were inhibited in a dose dependent manner by detergent solubilized mouse central nervous system myelin proteins as a tissue culture substrate. These inhibitory effects could be neutralized by the monoclonal antibody IN-1 directed against the neurite growth inhibiting proteins NI-35 and NI-250. Separation of the detergent soluble proteins of bovine spinal cord by an anion exchange column showed that the peaks of inhibitory activity for the two cell lines overlapped, such that the PC12 cells were inhibited by a larger number of fractions comprising those inhibitory for 3T3 cells. Neurite outgrowth of PC12 cells was not influenced by the myelin associated glycoprotein, MAG.     

The neural cell adhesion molecule (NCAM) in development and plasticity of the nervous system

—The neural cell adhesion molecule (NCAM) is a member of the immunoglobulin superfamily and is strongly expressed in the nervous system. NCAM is found in three major forms, of which two—NCAM-140 and NCAM-180—are transmembrane proteins, while the third—NCAM-120—is attached to the membrane via a glycosylphosphatidyl inositol anchor. In addition, soluble NCAM forms exist in brain, cerebrospinal fluid, and plasma. NCAM mediates cell adhesion through homophilic as well as through heterophilic interactions. Following NCAM binding, transmembrane signalling is believed to be activated, resulting in increased intracellular calcium. By mediating cell adhesion to other cells and to the extracellular matrix and by activating intracellular signaling pathways, NCAM influences cell migration, neurite extension, and fasciculation, and possibly formation of synapses in the brain. From studies on NCAM knock-out mice, NCAM have been shown to be crucial for the formation of the olfactory bulb and the mossy fiber system in the hippocampus. In addition, NCAM is important for neuronal plasticity in the adult brain associated with learning and regeneration.     

Laminin overrides the inhibitory effects of peripheral nervous system and central nervous system myelin-derived inhibitors of neurite growth

Axon growth inhibitory proteins associated with central nervous system (CNS) myelin are responsible in part for the absence of long distance axon regeneration in the adult mammalian CNS. We have recently reported that myelin-associated glycoprotein (MAG), which is also present in peripheral nerves, is a potent inhibitor of neurite growth. This was surprising given the robust regenerative capacity of peripheral nerves. We now provide evidence that myelin purified from peripheral nerve also has neurite growth inhibitory activity. However, this activity can be masked by laminin, which is a constituent of the Schwann cell basal lamina. We also report that laminin, which is largely absent from the normal adult mammalian CNS, when added to purified CNS myelin, can override the neurite growth inhibitory activity in CNS myelin. These results have important implications for the development of strategies to foster axon regeneration in the adult mammalian CNS where multiple growth inhibitors exist. © 1995 Wiley-Liss, Inc.     

Accelerated regenerative neurite formation by a neuronal surface epitope reactive with the monoclonal antibody, Leu 7

A family of glycoproteins sharing an epitope with myelin associated glycoprotein as recognized by the monoclonal antibody Leu 7 (HNK-1) has been found to be present on neurons grown in culture from embryonic chicks and rats. Immunofluorescent staining demonstrates that, in vitro, 100% of the neurons from dorsal root ganglia and spinal cord from 7-8 day chick embryos react with Leu 7. Analysis of in vitro regenerative neurite formation by neurons on substrates enriched with Leu 7 showed accelerated regenerative process formation under limiting conditions. These results indicate that the Leu 7 epitope on neurons is appropriate for substrate adhesion and promotes rapid process extension.     

Reorganization of the Cytoskeleton in Rat Neurons Following Stimulation With Excitatory Amino Acids In Vitro

The state of neuronal microtubule polymerization is influenced by microtubule-associated proteins such as MAP2, which is specifically localized within neuronal dendrites and cell bodies. We have demonstrated that stimulation of spinal cord or cortical neurons in vitro with excitatory amino acids results in a dramatic modification of the neuronal cytoskeleton as monitored with antibodies against MAP2 and tubulin. Stimulation of cultures with glutamate receptor agonists induced a reorganization of MAP2 immunoreactivity into a distinctive network of bundles within certain neuronal cell bodies and their proximal neurites. The effect was not abolished by depolymerizing drugs such as nocodazole, or protein synthesis inhibitors. The effect was dependent upon the entry of sodium following depolarization and was not associated with neuronal damage. We suggest that in neurons the state of the neuronal cytoskeleton can be modulated by glutamate receptor activation acting through MAP2.     

人基因组DNA片段对胚胎小鼠脊髓培养神经元的影响

目的：研究人基因组ＤＮＡ对培养的小鼠脊髓神经元活性及突起生长的影响．方法：用酚－氯仿抽提法从人胚脑中提取人基因组ＤＮＡ片段,用此ＤＮＡ片段加至体外培养的胚胎小鼠脊髓神经元培养液中,培养３ｄ后作ＭＴＴ实验,ＮＳＥ染色,图像分析神经元突起的长度．结果：实验组的神经元突起长度明显长于对照组而活性与对照组无明显差异．结论：提示人基因组ＤＮＡ或其某些片段可促进神经元突起的生长而对神经元活性无影响