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F Aloisi

Publications and source records attributed to F Aloisi.

At least 55 records · Page 3Linked to original sources
PubMed1992

Production of hemolymphopoietic cytokines (IL-6, IL-8, colony-stimulating factors) by normal human astrocytes in response to IL-1 beta and tumor necrosis factor-alpha.

Astrocyte-enriched populations were established from human embryonic brain analyzed for their ability to synthesize cytokines potentially relevant for mechanisms of inflammation and immunity in the brain. Unstimulated astrocytes did not secrete significant IL-6, IL-8, macrophage CSF (M-CSF), granulocyte-macrophage CSF (GM-CSF), or granulocyte-CSF (G-CSF), as determined by specific ELISA and/or bioassay. With the exception of M-CSF mRNA, transcripts for the above factors were not detected in unstimulated astrocytes. On exposure of human astrocytes to IL-1 beta, high levels of IL-6, IL-8, M-CSF, G-CSF, and GM-CSF mRNAs were detected; moreover, active secretion of all the above cytokines was demonstrated. TNF-alpha was also able to stimulate IL-6, IL-8, M-CSF, GM-CSF, and G-CSF synthesis and secretion, but was generally less potent than IL-1 beta. No IL-3 mRNA or protein was detected in unstimulated or cytokine-treated astrocytes. IL-1 alpha and IL-1 beta mRNAs and proteins were not detected in unstimulated astrocytes, but were present in very small amounts after stimulation with TNF-alpha/IL-1 beta. No IL-6, M-CSF, GM-CSF, G-CSF, or IL-8 were induced by IL-1 beta or TNF-alpha in early primary cultures, which mainly contain undifferentiated neuronal/glial progenitor cells. These studies demonstrate for the first time the production of multiple cytokines by normal human astrocytes stimulated in culture by IL-1 beta and TNF-alpha. The capacity of human astrocytes to synthesize and release cytokines active on hemolymphopoietic cells supports the concept that these cells play an important role in the regulation of inflammatory and immune responses in a variety of brain pathologies.

Astrocytes↗
PubMed1992

Developmental appearance, antigenic profile, and proliferation of glial cells of the human embryonic spinal cord: an immunocytochemical study using dissociated cultured cells.

We have investigated the time of appearance of the earliest differentiating glial cell types of human spinal cord using a panel of antigenic markers to identify them in cultures from 6- to 9-week-old human embryos. Immunolabeling performed at 14 h in vitro with the O4 mAb, an early oligodendrocyte marker, showed the presence of oligodendrocytes during the 7th week of age. At 8 weeks only a few of the O4+ cells expressed galactocerebroside (GalC), a marker of more differentiated oligodendrocytes. All the O4+ and GalC+ cells were vimentin+ and some of the GalC+ cells were A2B5+, GD3+ and SSEA-1+. During the first week in vitro many of the O4+ cells exhibiting a more immature, bi- or tri-polar morphology incorporated [3H]thymidine into their nuclei. Cells expressing the astrocyte-specific marker GFAP could be first observed at 8 weeks; almost all of these GFAP+ cells, which should correspond to radial glia on the basis of the current literature, were vimentin+, A2B5+, GD3+, and SSEA-1+. At 2 days in vitro incorporation of [3H]thymidine could be shown in a small fraction of these cells. The finding that radial glia and oligodendrocytes expressed similar antigenic features and the additional observation that a small, but consistent fraction of the cells were simultaneously labeled by O4 and anti-GFAP antibodies support the hypothesis that, in the human spinal cord, radial glial cells can give rise to both oligodendrocytes and astrocytes; in this respect, radial glial cells may be similar to the A2B5+, GD3+, vimentin+ bipotential glial progenitors previously identified in cultures from developing rat CNS, which also express A2B5, GD3, and vimentin.

Antibodies↗
PubMed1992

Interaction between oligodendroglia and immune cells: mitogenic effect of an oligodendrocyte precursor cell line on syngeneic T lymphocytes.

We analyzed cellular interactions between T lymphocytes and a recently established immortal glial line, L3 that retains several properties of immature oligodendrocytes (Aloisi et al., J Neurosci Res 27:16-24, 1990). L3 oligodendrocytes (L3-OL) cannot be induced to express class II antigens, nor do they specifically present antigen to syngeneic specific T lymphocyte. However, L3-OL strongly enhance the proliferation of freshly activated, interleukin-2(IL-2)-dependent T-line lymphocytes and concanavalin A (ConA)-activated lymphoblasts, irrespective of their antigen specificity or surface phenotype (CD4+ or CD8+). Resting and some activated T cells were susceptible to the mitogenic effect of L3-OL only in the presence of exogenous IL-2, not of other cytokines. The mitogenic effect of L3-OL did not depend on cell viability. It was observed in paraformaldehyde-fixed L3-OL cells and in membrane preparations, but not in culture supernatant. Neither intact L3-OL cells nor membrane preparations had direct IL-2 activity. The conclusion that the mitogenic effect of L3-OL cells is exerted by membrane structures acting as a costimulatory factor(s) of IL-2 is supported by the finding that it is largely blocked by a monoclonal anti-IL-2 receptor antibody. The effect is distinct from membrane-bound IL-1, membrane-bound tumor necrosis factor-alpha (TNF-alpha), IL-3, or IL-6 and cannot be reconstituted by these cytokines.

Animals↗
PubMed1992

Astrocyte cultures from human embryonic brain: characterization and modulation of surface molecules by inflammatory cytokines.

Astrocyte-enriched cultures were established upon passaging of primary cultures from the myelencephalon and mesencephalon of 7-9-week-old human embryos. Immunocytochemical analysis showed that third-fourth passage cultures were composed of a highly enriched population of proliferating, epithelioid cells, up to 90% of which expressed glial fibrillary acidic protein (GFAP); no macrophages and very few fibroblasts (less than 2%) were present. GFAP expression and proliferation declined upon further culturing in serum-containing medium but could be transiently reinduced by growing the cells in a serum-free chemically defined medium. Large numbers of GFAP+ astrocytes were obtained from each embryo and could be stored frozen and recultured. Using flow cytometric analysis, human astrocyte cultures were examined for basal and cytokine [interferon-gamma (IFN-gamma), interleukin-1 beta (IL-1 beta), and tumor necrosis factor-alpha (TNF-alpha)]-induced expression of molecules that may be involved in astrocyte-T-lymphocyte interactions. Cultured human astrocytes spontaneously expressed major histocompatibility complex (MHC) class I antigens and variable levels of MHC class II; MHC class I levels were increased upon IFN-gamma and TNF-alpha treatment, whereas MHC class II antigens were induced on most of the astrocytes by IFN-gamma. Among the molecules involved in antigen-independent interactions between T lymphocytes and target cells, lymphocyte function-associated molecule-3 (LFA-3) was spontaneously expressed by most cultured human astrocytes, whereas intercellular adhesion molecule-1 (ICAM-1) was present at variable levels in non-stimulated astrocytes and was greatly induced by IFN-gamma, TNF-alpha, and IL-1 beta. In this study we also show that the above cytokines upregulate astroglial expression of adhesion molecules of the integrin family (VLA-1, VLA-2, and VLA-6) that may be involved in astrocyte-extracellular matrix interaction and play a role in the astrocyte reactive changes occurring at sites of brain injury and inflammation. The human astrocyte cultures developed here represent a useful in vitro model to further investigate mechanisms involved in bidirectional communication between central glia and cells of the immune system.

Astrocytes↗
PubMed1991

Is the oligodendroglial differentiation of bipotential oligodendrocyte-type 2 astrocyte progenitors promoted by autocrine factors?

When immature O-2A (oligodendrocyte-type 2 astrocyte) lineage cells purified from rat mixed cortical glial cultures were subcultured at low density in 10% fetal calf serum (FCS)-containing medium they largely differentiated into type-2 astrocytes. When the same number of cells was subcultured at high density in the same volume of medium the proportion of O-2A progenitors differentiating into oligodendrocytes was substantially increased. The possibility that oligodendrocyte differentiation in high-density cultures is facilitated by autocrine factors is supported by the observation that a medium conditioned by high-density subcultures of purified O-2A cells contains high molecular weight (greater than 30 kDa), non-mitogenic factor(s) capable of inducing a rapid differentiation of immature 0-2A cells into oligodendrocytes even in low-density cultures.

Animals↗
PubMed1991

Heterotypic and homotypic cellular interactions influencing the growth and differentiation of bipotential oligodendrocyte-type-2 astrocyte progenitors in culture.

Cell populations highly enriched in oligodendrocyte-type-2 astrocyte (O-2A) progenitors (so defined by their ability to bind the monoclonal antibodies LB1 and O4, and by the lack of expression of the differentiated glial markers galactocerebroside and glial fibrillary acidic protein (GFAP) were obtained from rat mixed cortical glial cultures. The O-2A progenitors were grown at low density (2 X 10(4) cells/cm2) in BME + 10% fetal calf serum (FCS) on a poly-L-lysine (PLL) substrate (controls) or on a substrate of purified type-1 astrocytes (AS) killed by air drying (K-AS), in order to analyze the effects of the interaction between the two cell types on the growth and differentiation of the immature O-2A cells, independently of the mitogenic soluble factors (e.g., platelet-derived growth factor; see Raff, 1989, Science 243, 1450-1455) secreted by type-1 AS. While on PLL most of the progenitors differentiated into GFAP+ type-2 AS within 1 week, on K-AS they largely differentiated into GalC+ oligodendrocytes (OL). On the latter substrate, however, the precursors achieved a higher density, due to higher proliferative activity. The additional observation, that when immature O-2A cells were seeded at high density (greater than 5 X 10(4) cells/cm2) on PLL their differentiation into OL was much more pronounced than in cultures of lower density, indicates that there is a close correlation between the density of immature O-2A cells and lineage decision, and that the increased OL differentiation of the immature O-2A cells on K-AS is at least partly related to the higher density achieved by the cells on this substrate. The enhanced proliferation of immature O-2A cells on K-AS did not appear to be related to platelet-derived growth factor or fibroblast growth factor remaining attached to the substrate, nor to known components of the extracellular matrix (ECM), such as heparan sulfate, chondroitin sulfate, laminin, or fibronectin, but was probably due to other components of a polypeptide nature present in the ECM produced by type-1 AS. A cell-free ECM was in fact almost as mitogenic as the K-AS substrate, and the mitogenic activities of both K-AS and AS-ECM were similarly inhibited by a set of enzymatic (pronase, trypsin) and physicochemical (heat, pH) treatments.

Animals↗
PubMed1990

Establishment of a permanent rat brain-derived glial cell line as a source of purified oligodendrocyte-type 2 astrocyte lineage cell populations.

A permanent glial cell line (L3) has been established from mixed glial cultures obtained from neonatal rat forebrain by repetitive passaging and selection of the process-bearing cells growing on top of a flat cell monolayer. Continuous propagation of the process-bearing cells was supported by the flat cells, of presumed astroglial origin, which were present in negligible amounts following each passage but then grew and formed a basal, feeder layer. Throughout a culture period of over 2 years, the L3 cells have maintained a stable morphological and antigenic phenotype. In serum-containing culture medium, most of the process-bearing cells expressed at the same time features of immature oligodendrocytes (O4 positivity) and of astrocytes [glial fibrillary acidic protein (GFAP) positivity]. A smaller proportion of them was labeled by the monoclonal antibody LB1. LB1+ or O4+ cells were rarely GFAP-, and GFAP+ cells were rarely LB1- or O4-. GalC+ oligodendrocytes were seen only occasionally, but the proportion of these cells increased up to 30% upon culturing in chemically defined medium containing 0.5% fetal calf serum. The L3 process-bearing cells accumulated the neurotransmitter gamma-aminobutyric acid (GABA), expressed the proteoglycan chondroitin sulfate, and responded to the mitogenic action of platelet-derived growth factor (PDGF) and fibroblast growth factor (FGF). All these properties are characteristic of cells belonging to the O-2A (oligodendrocyte-type 2 astrocyte) cell lineage. The L3 flat cells were largely negative for the glial markers tested, but resembled type 1 astrocytes in their ability to support the growth of O-2A lineage cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

Differentiation of bipotential glial precursors into oligodendrocytes is promoted by interaction with type-1 astrocytes in cerebellar cultures.

The differentiation of bipotential precursors of oligodendrocytes (OL) and type-2 astrocytes (AS) was followed in primary cultures from 8-day postnatal rat cerebellum by labeling the cells with the antibodies LB1 (which binds to the surface disialoganglioside GD3 present in glial precursors, type-2 AS, and immature OL), O4 (a marker of immature and mature OL binding to surface sulfatide), anti-galactocerebroside (GalCer, a marker of OL), and anti-glial fibrillary acidic protein (GFAP, a marker of AS). Two hours after plating, hardly any LB1+, GFAP+ cells were detectable, 40% of the O4+ cells were GalCer+, and none of the O4+ cells were GFAP+. Upon culturing cells plated at a density of 1 x 10(5) cells per cm2 in the presence of fetal calf serum, most of the LB1+ precursors differentiated into type-2 AS, even if most of them had already expressed the O4 antigen. Thus, in culture, most type-2 AS seem to derive from progenitor cells that were differentiating in vivo into OL. In higher density cultures (2.5 x 10(5) cells per cm2), however, many precursors differentiated into GalCer+ OL, rather than into AS. As a possible source of the signals responsible for the behavior of the glial precursors in high-density cultures, we focused our attention on type-1 AS, the most abundant cell type in the cultures. We found that, in low-density cultures maintained for 5-7 days in a medium conditioned by type-1 AS, the proliferation of the precursors was enhanced and their differentiation into OL or AS was prevented. In contrast, when cerebellar cells were coplated with type-1 AS dissociated from purified cultures, not only did the precursors proliferate more than in control cultures, but also a larger proportion of them differentiated into GalCer+ OL. In conclusion, type-1 AS appear to facilitate the differentiation of bipotential glial precursors into OL through direct cell-cell interactions. The influence of type-1 AS on the differentiation of the LB1+ and O4+ precursors is supported also by experiments with glial cortical cultures.

Animals↗
PubMed1987

Differentiation of cerebellar bipotential glial precursors into oligodendrocytes in primary culture: developmental profile of surface antigens and mitotic activity.

We have analyzed the changes in surface antigenic properties of cerebellar bipotential precursors of oligodendrocytes and type-2 astrocytes during their differentiation into oligodendrocytes in serum-free cultures and the relationship between antigen expression and proliferation of these cells. Double immunofluorescence experiments with different monoclonal antibodies (mabs) performed at various stages in vitro and immunocytolysis experiments provided evidence for the following antigenic developmental profile: at early stages in culture the progenitor cells are recognized by the mabs A2B5 and LB1 (which bind to surface gangliosides) but not by other mabs known to label immature or mature oligodendrocytes (04, 01, and anti-galactocerebroside [GalC]). A few days later, the precursors start to express the 04 antigen; at this stage they maintain a bipotential nature and, in the presence of serum, they differentiate into type-2 astrocytes. If maintained in serum-free medium, the progenitor cells enter the oligodendrocyte differentiation compartment, acquiring GalC positivity. Soon after becoming GalC+, the cells lose both bipotentiality and the surface antigens binding A2B5 and LB1. They conserve, however, the antigen binding 04. Experiments of [3H]thymidine autoradiography combined with immunofluorescence showed that a greater proportion of the LB1+ cells incorporated the radioactive nucleoside into their nuclei as compared to the 04+ cells. No incorporation was present in GalC+ oligodendrocytes.

Animals↗
PubMed1987

Glial conditioned media inhibit the proliferation of cultured rat cerebellar astrocytes.

Conditioned medium (CM) obtained from rat cerebellar astrocytes cultured in a serum-containing medium was able to inhibit [3H]thymidine incorporation into proliferating astrocytes, when compared to fresh medium. This effect could be attributed to two fractions of the CM with different molecular weights. The low molecular weight fraction (Mr less than 1,000) inhibited the cellular transport of the labeled precursor, without significantly affecting cell proliferation. The high molecular weight fraction (Mr greater than 10,000) showed a strong inhibitory effect on astrocyte proliferation, which was documented using different assay techniques: i) [3H]thymidine incorporation performed in conditions preventing the effects of CM on transport; ii) [3H]thymidine autoradiography; iii) determination of the DNA content of the cultures. The inhibitory activity was present in media conditioned by non proliferating astrocytes treated with the antimitotic cytosine arabinoside, but not in media conditioned by neuron-enriched cultures nor in a chemically defined (N2) CM. The antiproliferative activity of astrocyte CM could be due either to a rapid depletion of mitogenic factors present in serum, or, to a secretion of growth inhibitory factor(s) by cultured astrocytes.

Animals↗
PubMed1986

Developmental features of rat cerebellar neural cells cultured in a chemically defined medium.

We studied some aspects of the differentiation of rat cerebellar neural cells obtained from 8-day postnatal animals and cultured in a serum-free, chemically defined medium (CDM). The ability of the cells to take up radioactive transmitter amino acids was analyzed autoradiographically. The L-glutamate analogue 3H-D-aspartate was taken up by astroglial cells, but not by granule neurons, even in late cultures (20 days in vitro). This is in agreement with the lack of depolarization-induced release of 3H-D-aspartate previously observed in this type of culture. In contrast, 3H-(GABA) was scarcely accumulated by glial-fibrillary-acidic-protein (GFAP)-positive astrocytes, but taken up by glutamate-decarboxylase-positive inhibitory interneurons and was released in a Ca2+-dependent way upon depolarization: 3H-GABA evoked release progressively increased with time in culture. Interestingly, the expression of the vesicle-associated protein synapsin I was much reduced in granule cells cultured in CDM as compared to those maintained in the presence of serum. These data would indicate that in CDM the differentiation of granule neurons is not complete, while that of GABAergic neurons is not greatly affected. Whether the diminished differentiation of granule cells must be attributed only to serum deprivation or also to other differences in the composition of the culture medium remains to be established. 3H-GABA was avidly taken up also by a population of cells which were not recognized by antibodies raised against GFAP, glutamate decarboxylase, and microtubule-associated protein 2. These cells exhibited a stellate morphology, were stained by the monoclonal antibody A2B5, and have been characterized elsewhere [Levi et al, 1986] as bipotential precursors of oligodendrocytes and of a subpopulation of astrocytes bearing a stellate shape and capable of high-affinity 3H-GABA uptake.

Animals↗
PubMed1985

Characterization of GABAergic neurons in cerebellar primary cultures and selective neurotoxic effects of a serum fraction.

The morphological and functional differentiation of GABAergic interneurons present in cerebellar primary cultures has been examined by means of [3H]gamma-aminobutyric acid (GABA) autoradiography and [3H]GABA depolarization-evoked release. At 2 days in vitro these neurons showed scarce accumulation of radioactivity and no Ca2+-dependent K+-evoked or veratridine-induced release of [3H]GABA. At 5 days in vitro GABAergic interneurons appeared more intensely labeled and had grown out long and often branched neuritic processes; a large Ca2+-dependent release of [3H] GABA could be evoked by high K+. At later stages the progressive increase in labeling and branching of the neuritic processes was paralleled by a further increase in the amount and Ca2+ dependence of [3H]GABA release; a tetrodotoxin-sensitive, veratridine-stimulated release was also demonstrated. The [3H]GABA-accumulating stellate astrocytes present in the culture were not responsible for the observed release of the amino acid. GABAergic neurons were also identified by indirect immunofluorescence, using antibodies to the specific marker glutamic acid decarboxylase. Total renewal of the culture medium at 7 days in vitro caused a drastic (90%) reduction in the number of GABAergic neurons and a concomitant decrease in the amount of [3H]GABA uptake and release in the cultures. The disappearance of GABAergic neurons was caused by a low molecular weight (Mr less than 1000) fraction of the serum used to supplement the basal culture medium. This serum component did not significantly influence the survival of the major neuronal population of the culture (the granule cells) and appeared to be selectively toxic for GABAergic neurons only after they had reached a quite advanced degree of morphological and functional differentiation in vitro. The toxic activity was no longer present in neuronal or glial conditioned media.

Animals↗
PubMed1984

Autoradiographic localization and depolarization-induced release of acidic amino acids in differentiating cerebellar granule cell cultures.

Granule cells from 8-day-old rat cerebella were grown in basal Eagle's medium with 10% fetal calf serum, for 2,5,8 or 12 days in vitro (DIV), in conditions giving a purity greater than 90%. The results obtained can be summarized as follows: (1) Light microscopic autoradiography showed that cultured granule cells and their processes can accumulate the glutamate analog [3H]D-aspartate once they have reached an advanced degree of morphological differentiation (8 and 12 DIV), but, even then, only a limited number of cells was heavily labeled. In contrast, astrocytes were heavily labeled at all stages. (2) Calcium-dependent, high [K+]-induced release, or tetrodotoxin-sensitive, veratridine-induced release of [3H]D-aspartate from granule cell-enriched cultures was detectable only in cultures of 8 or 12 DIV. (3) When subject to 3 consecutive depolarizations, cultured granule cells maintained their ability to release [3H]D-aspartate and endogenous glutamate almost unchanged. (4) Newly synthesized [3H]glutamate was autoradiographically localized in both neurons and astrocytes (the latter, however, were not preferentially labeled as with [3H]D-aspartate), but was specifically released from neuronal structures (perikarya and processes) by depolarizing stimuli.

Animals↗
PubMed1983

Substrate specificity and developmental aspects of a presynaptic GABA receptor regulating glutamate release in the rat cerebellum.

In order to better characterize the presynaptic GABA receptors regulating glutamate release in the cerebellum [Levi and Gallo, 1981], a number of GABA agonists and GABA transport inhibitors were tested for their ability to potentiate the depolarization-induced release of the glutamate analog D-[3H]aspartate from superfused cerebellar synaptosomes. Of all the compounds tested, only those which are known to interact specifically with GABA receptors were effective when tested on synaptosomal preparations. The order of effectiveness found was the following: muscimol congruent to 3-APS greater than or equal to P4S greater than isoguvacine greater than THIP. GABA uptake inhibitors were unable to enhance D-[3H]aspartate evoked release from synaptosomes, but were effective when tested in cerebellar slices; in the latter case, the activation of the GABA receptors may be achieved indirectly, through an increase of the extracellular GABA concentrations. The substrate specificity of the presynaptic GABA receptors regulating cerebellar acidic amino acid release appears to be similar to that reported for GABA receptors in radioligand binding studies and for GABA autoreceptors. Studies on synaptosomes from immature cerebella suggested that the presence of the potentiating effect on the acidic amino acid release by GABA agonists is correlated with the development of the parallel fiber terminals, which are believed to be the main site from which glutamate is released in the adult cerebellum.

Animals↗
PubMed1983

Muscimol potentiation of acidic amino acid release from cerebellar synaptosomes is chloride dependent.

In previous studies we have shown that the depolarization-induced release of preaccumulated acidic amino acids and newly synthesized glutamate from cerebellar synaptosomal preparations is potentiated by gamma-aminobutyric acid (GABA) agonists through a GABAergic presynaptic mechanism. Here we report a systematic analysis of the ionic requirements of the potentiating effect of muscimol on the high K+-evoked release of D-[3H]aspartate. Our studies show that: Ca2+, Na+, and Mg2+ are not required for muscimol to exert its effect; a depolarizing concentration of K+ is a necessary, but not sufficient, condition to observe the presynaptic effect in question; and a minimal Cl- concentration (50-70 mM) is also required. A possible model based on these findings is proposed.

Animals↗
PubMed1982

Selective release of glutamate from cerebellar granule cells differentiating in culture.

The aim of the present study was to assess whether endogenous and newly synthesized glutamate can be released from differentiating cultured cerebellar granule cells in a way compatible with a neurotransmitter role. Granule cells from 8-day-old rat cerebella were grown in basal Eagle's medium with 10% fetal calf serum for 2-12 days in vitro (DIV), then washed with Krebs-Ringer medium, and labeled for 45 min with tracer amounts of radioactive glutamine. Subsequently, the release of endogenous glutamate and of newly formed radioactive glutamate was measured in basal conditions and upon depolarization with elevated K(+) concentration or veratridine. At 2 DIV, the release of endogenous and newly synthesized glutamate evoked by high K(+) concentration was small and Ca(2+) independent, but it progressively and steadily increased (up to 8- to 10-fold) and became Ca(2+) dependent (up to 80-85%) at later stages (4, 8, and 12 DIV). Veratridine was almost ineffective with cells at 2 DIV but greatly increased glutamate release (endogenous and neosynthesized) at 8 DIV, and its action was totally antagonized by tetrodotoxin. The level and synthesis of glutamate remained fairly constant in cells from 2 to 12 DIV. gamma-Aminobutyric acid synthesis from radioactive glutamine was about 3% of that of glutamate, and gamma-aminobutyric acid release (endogenous and neosynthesized) was not measurable. Aspartate synthesis was about 10% of that of glutamate, and the high K(+) concentration-evoked release of this amino acid was modest and scarcely affected by Ca(2+). Neither high K(+) concentration nor veratridine was able to induce glutamate release from confluent cerebellar astrocyte cultures at 14 DIV, although the level and synthesis of the amino acid were comparable to those in granule cells. In conclusion, the data show that a stimulus-coupled release of endogenous and neosynthesized glutamate is progressively expressed by cerebellar granule cells differentiating in culture, and this strongly supports the concept that glutamate is the neurotransmitter of these cells.

Animals↗