ISSN:0894-1491    

DOI:10.1002/glia.440110202

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractGABA receptors are distributed widely throughout the central nervous system on a variety of cell types. It has become increasingly clear that astrocytes, both in cell culture and tissue slices, express abundant GABAAreceptors. In astrocytes, GABA activates Cl−‐specific channels that are modulated by barbiturates and benzodiazepines; however, the neuronal inverse agonist methyl‐4‐ethyl‐6, 7‐dimethoxy‐β‐carboline‐3‐car‐boxylate enhances the current in a subpopulation of astrocytes. The properties of astrocytic GABAAreceptors, therefore, are remarkably similar to their neuronal counterparts, with only a few pharmacological exceptions. In stellate glial cells of the pituitary pars intermedia, GABA released from neuronal terminals activates postsynaptic potentials directly. The physiological significance of astrocytic GABAA‐receptor activation remains unknown, but it may be involved in extracellular ion homeostasis and pH regulation. At present, there is considerably less evidence for the presence of GABABreceptors on astrocytes. The data that have emerged, however, indicate a prominent role for second‐messenger regulation by this recept

ISSN:0894-1491    

DOI:10.1002/glia.440110203

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractWe have analyzed the molecular and biophysical properties of glutamate‐gated channels in cells of the oligodendrocyte lineage, using both the CG‐4 primary cell line (Louis et al: J. Neurosci. Res. 31:193‐204, 1992a) and oligodendrocyte progenitors purified from the rat cerebral cortex. CG‐4 progenitor cells, as well as primary progenitors, were stained with a specific anti‐GABA antibody. In whole‐cell patch‐clamp recordings, rapid perfusion of the agonists L‐glutamate, kainate, and AMPA produced rapidly desensitizing currents in CG‐4 cells. NMDA was ineffective. Both rapidly desensitizing and steady‐state components of responses to kainate were inhibited by the kainate/AMPA receptor antagonist CNQX. Northern blot analysis of total mRNA isolated from CG‐4 cells revealed co‐expression of both AMPA‐ and kainate‐preferring glutamate receptor subunits. The activation of glutamate receptors in CG‐4 cells caused a rapid and transient elevation of mRNAs for the immediate early gene N

ISSN:0894-1491    

DOI:10.1002/glia.440110204

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractGlial cells in vitro express at least two types (H1and H2) of histamine receptors and three types (EP, FP, and TP) of prostanoid receptors. The receptors expressed by glial cells differ according to the cell type and source in the brain. Further‐more primary astrocytes of same type derived from the same brain region are composed of heterogeneous subpopulations expressing different subsets of receptors. Fura‐2 based Ca2+microscopy revealed that astrocyte processes are important sites for histamine‐induced Ca2+signalling. Histamine and prostanoid receptors on glial cells may play important roles in the actions of histamine and prostanoids in the central nervous system. © 1994 Wiley‐L

ISSN:0894-1491    

DOI:10.1002/glia.440110205

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractAstroglial cells derived from the mammalian central nervous system contain a wide variety of peptide receptors, including specific sites for angiotensin II (AII) and atrial natriuretic peptide (ANP). The AII receptors present in these cells are primarily of the AT1subtype. The ANP receptors present in these cells consist of a mix of ANP‐A and ANP‐B sites (“biological receptors”) and also ANP‐C sites (“clearance receptors”). Available evidence indicates that activation of AII receptors results in a stimulation of astroglial proliferation, whereas ANP has an antiproliferative effect in these cells. Intracellular pathways which may mediate these effects of AII and ANP on cell proliferation are discussed, including the presentation of novel data on the activation of protein kinase C and of glucose uptake by AII. We also consider the possibility that the opposing actions of AII and ANP on astroglial proliferation may represent another facet of the mutual antagonism between these two peptides, which has been observed throughout mammalian systems. © 1994 W

ISSN:0894-1491    

DOI:10.1002/glia.440110206

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractGiven what evidence there is for the molecular and functional nature of cytokines and their cognate binding proteins in the immune system and the emerging similarities or even identities for these ligands and receptors in the nervous system, two general models may be relevant. The first emerging pattern is that receptors for related but distinct trophic factors in the CNS are in many instances multichain complexes with one or more shared components. The shared components of the receptor complex may be either signal‐ or nonsignal‐transducing chains. A second emerging motif is that related ligands and related receptors fall into gene families. Undoubtedly, these models will facilitate the cloning of novel members of these families whose function is quite specific to the nervous system and in particular to glial cells. This article will review the function of the receptors for cytokines and families of differentiation/survival/growth factors as they operate on astrocytes, microglia, and oligodendrocytes in development, health, and disease. © 1994 Wiley‐Lis

ISSN:0894-1491    

DOI:10.1002/glia.440110207

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractActivation and proliferation of glial cells are common events in the pathology of the nervous system. Although we are only beginning to understand the molecular signals leading to glial activation in vivo, there is increasing evidence that growth factors and their receptors may play an important part. In this paper we summarize the data on the pathophysiology of glial growth factor receptors and their ligands in the central and peripheral nervous systems. © 1994 Wiley‐Liss, I

ISSN:0894-1491    

DOI:10.1002/glia.440110208

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractIt is becoming apparent that astrocytes carry out a large number of different functions in brain and are able to modify their characteristics throughout life, that is they exhibit a high degree of plasticity in their phenotype. For example, the morphology of astrocytes changes markedly during neuronal migration, maturation, and degeneration. It is conceivable that these cells must constantly adjust their abilities to meet changes in brain environment. Several examples of astrocytic plasticity are presented in this review. First, the ability of astrocytes to recognize neuronal signals can change qualitatively as well as quantitatively; evidence suggests that the expression of glial receptors may be developmentally regulated by both intrinsic and extrinsic signals. Second, the expression of adrenergic receptors by astrocytes in adult brain can change in response to neuronal degeneration. The up‐regulation of β‐adrenergic receptors in this case suggests that these receptors play a role in function of reactive astrocytes. Finally, glial morphology can be reciprocally regulated by neurotransmitters such as norepinephrine and glutamate. This reciprocal regulation may be significant since both ß‐adrenergic receptors and glutamate transporters are found predominantly in astrocytes in the brain. The change in glial morphology may also affect neuronal activity by changing the volume of the extracellular space. © 1994 Wiley

ISSN:0894-1491    

DOI:10.1002/glia.440110209

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractGlial cells, although non‐excitable, express a wealth of voltage‐activated ion channels that are typically characteristic of excitable cells. Since these channels are also observed in acutely isolated cells and in brain slices, they have to be considered functional in the intact brain. Numerous studies over the past 10 years have yielded detailed characterizations of glial channels permitting comparison of their properties to those of their neuronal counterparts. While for the most part such comparisons have demonstrated a high degree of similarity, they also provide evidence for the expression of some uniquely glial ion channels. An increasing number of studies indicate that the expression of “glial” channels is influenced by the cells' microenvironment. For example, the presence of neurons can induce or inhibit (depending on the preparation and type of channel studied) the expression of glial ion channels. Like ion channels in excitable cells, glial channels can be functionally regulated by activation of second‐messenger pathways, allowing for short‐term modulation of their membrane properties. Although the extent to which most of the characterized ion channels are involved in glial function is presently unclear, a growing body of data suggests that certain channels play an active role in glial function. Thus inwardly rectifying K+channels in concert with delayed rectifying K+channels are thought to be involved in the removal and redistribution of excess K+in the brain, a process referred to as “spatial buffering.” Glial K+channels may also be crucial in modulating glial proliferation. Cl−channels and stretch‐activated cation channels are believed to be involved in volume regulation. Na+channels appear to be important in fueling the glial Na+/K+‐pump, and Ca2+channels are likely involved in numerous cellular events in which intracellular Ca2+is a critical second messenger.

ISSN:0894-1491    

DOI:10.1002/glia.440110210

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractAstrocytes respond to the excitatory neurotransmitter glutamate with dynamic spatio‐temporal changes in intracellular calcium [Ca2+]i. Although they share a common wave‐like appearance, the different [Ca2+]ichanges‐‐an initial spike, sustained elevation, oscillatory intracellular waves, and regenerative intercellular waves‐‐are actually separate and distinct phenomena. These separate components of the astrocytic Ca2+response appear to be generated by two different signal transduction pathways. The metabotropic response evokes an initial spatial Ca2+spike that can propagate rapidly from cell to cell and appears to involve IP3. The metabotropic response can also produce oscillatory intracellular waves of various amplitudes and frequencies that propagate within cells and are sustained only in the presence of external Ca2+. The ionotropic response, however, evokes a sustained elevation in [Ca2+]iassociated with receptor‐mediated Na+and Ca2+influx, depolarization, and voltage‐dependent Ca2+influx. In addition, the ionotropic response can lead to regenerative intercellular waves that propagate smoothly and nondecrementally from cell to cell, possibly involving Na+/Ca2+exchange. All these astrocytic [Ca2+]ichanges tend to appear wave‐like, traveling from region to region as a transient rise in [Ca2+]i. Nevertheless, as our understanding of the cellular events that underlie these [Ca2+]ichanges grows, it becomes increasingly clear that glutamate‐induced Ca2+signaling is a composite of separate and distinct phenomena, which may be distinguished not based on appearance alone, but rather on their underlying mechanisms. ©

ISSN:0894-1491    

DOI:10.1002/glia.440110211

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY