Expression of vimentin by cultured astroglia and oligodendroglia

The objective of this study was to determine whether vimentin expression by process-bearing astroglia and oligodendroglia cultured from neonatal rat cerebral cortex resembled that in brain where vimentin is common in immature astroglia and a few subpopulations of mature astroglia, but is absent in oligodendroglia. Vimentin expression was detected by immunofluorescence microscopy using a monoclonal antibody (V9) against porcine lens vimentin in combination with either antiserum against the astroglial marker, glial fibrillary acidic protein (GFAP), or with antiserum against the oligodendroglial marker, galactocerebroside (GC). Specificity of the antivimentin antibody was indicated on immunoblots of process-bearing cell proteins separated by two-dimensional polyacrylamide gel electrophoresis. Enrichment of cultures for either GFAP+ astroglia or GC+ oligodendroglia was achieved by supplementation of the culture medium with fetal calf serum at 10% or 0.5%, respectively. Process-bearing cells maintained in 10% serum exhibited heterogeneity in their expression of GFAP and vimentin. Approximately half of the cells were GFAP+/vimentin+ throughout the 2-week culture period examined. GFAP+/vimentin- cells were a minor population at early times (3-4 days) in culture, but accounted for 40% of process-bearing cells after 2 weeks. Cultures maintained in reduced (0.5%) serum and stained for GC and vimentin also exhibited heterogeneity. Both GC+/vimentin+ and GC+/vimentin- cells were observed, with vimentin+ cells composing two-thirds and one-half of the GC+ population after 3 and 6 days, respectively, in reduced serum. The high incidence of vimentin expression by process-bearing astroglia and oligodendroglia suggests that these cultures contain glia in a relatively early stage of development.(ABSTRACT TRUNCATED AT 250 WORDS)     

Regressive changes of astroglia in white matter lesions in cerebrovascular disease and Alzheimer’s disease patients

The pathogenesis of white matter lesions, which are frequently found in ischemic cerebrovascular disease and Alzheimer’s disease, remains unclear. Using light and electron microscopic immunohistochemistry for glial fibrillary acidic protein (GFAP) as a marker, the present study focused on the role of astroglia which show characteristic morphological alterations. Of 29 brains of patients with cerebrovascular disease and Alzheimer’s disease, 4 brains showed extensive swelling and vacuolation of white matter astroglia with their processes disintegrated and beaded (termed clasmatodendrosis). No such cells were observed in 6 control patients. Clasmatodendritic astroglia were not intensely eosinophilic using hematoxylin and eosin staining and included large lipophilic granules in their perikarya. These astroglia were immunoreactive for serum proteins such as immunoglobulins, fibrinogen and complement C3, C1q and C3d, as well as for proteins which are known to increase in reactive astroglia, such as vimentin, α-B crystallin, apolipoprotein-E and laminin. Double labeling for GFAP and microglial cell markers indicated that these cells were of astroglial lineage. Immunoelectron microscopy for GFAP revealed that clasmatodendritic astroglia had condensed chromatin, lysosomes and large membrane-bound osmiophilic cytoplasmic inclusions, which corresponded to the lipophilic granules observed with light microscopy. These cytochemical features collectively suggest that clasmatodendritic astroglia incorporate edema fluid and phagocytose cellular debris, and eventually degenerate as a result of cerebral edema. Received: 3 December 1996 / Revised, accepted: 24 January 1997     

Partial purification of a novel mitogen for oligodendroglia

A protein with a MW_app of 50–70 kDa isolated from the salt extract of crude membranes from neonatal rat brain increases the numbers of oligodendroglia in mixed glial cultures prepared from neonatal rat cerebral white matter. After partial purification by ion exchange and gel exclusion chromatography, and elution from an SDS-polyacrylamide gel, this protein ( “oligodendroglial trophic factor,” OTF) elicited half-maximal oligodendroglial recruitment at a concentration of 5 ng/mL. OTF is a mitogen for oligodendroglia, and to a lesser extent, for oligodendroglial progenitor (O2A) cells, but does not stimulate proliferation of astroglia, Schwann cells, or endoneurial fibroblasts. OTF, unlike platelet-derived growth factor (PDGF), is not an oligodendroglial survival factor. Antibodies against PDGF and basic fibroblast growth factor (bFGF) do not interfere with the accumulation of oligodendroglia induced by OTF. When OTF is given simultaneously with either PDGF or bFGF, there is an additive increase in the numbers of cells of the oligodendroglial lineage. © 1995 Wiley-Liss, Inc.     

Development of O4+/O1− immunopanned pro-oligodendroglia in vitro

In this study, O4+/O1− pro-oligodendroglia isolated by immunopanning from cerebral hemispheres of P3–P5 rats were evaluated during their maturation in culture. Immunopanning yielded 3–4×10⁵ cells/cerebrum, with 98% O4+ and 6% O1+. There was heterogeneity in the morphologies of immunopanned cells ranging from simple bipolar cells to more complex multipolar cells. As a first step in determining potential differentiative responses of mature oligodendroglia, we examined glial fibrillary acidic protein (GFAP) expression in response to fetal bovine serum (FBS) by cultures established from O4+/O1− immunopanned cells grown for 1, 14, or 21 days, exposed to 20% FBS for 6–7 days and fixed and immunostained on days 7, 21 or 28 in culture (DIC). When immunopanned cells were exposed to FBS following 1 day in serum-free medium, 88% expressed GFAP and when immunopanned cells were cultured for 14 days prior to FBS exposure, 78% expressed GFAP. By contrast, when cells were cultured for 21 days prior to FBS exposure (when a majority of the cells expressed O1 and myelin basic protein (MBP)), only 19% of the cells expressed GFAP (p<0.001). Cells that were O4+/GFAP− even in the presence of FBS often exhibited a mature oligodendroglial morphology. Among immunopanned cells that responded to FBS by expression of GFAP, both process-bearing (similar to type 2 astroglia) and flattened, polygonal (similar to type 1 astroglia) GFAP+ cells were observed. These results confirm the utility of immunopanning for the isolation of pro-oligodendroglia and demonstrate that oligodendroglia that develop in vitro from O4+/O1− immunopanned cells become resistant to GFAP induction by FBS.     

Neuroactive steroids regulate astroglia morphology in hippocampal cultures from adult rats

Recent evidence indicates that astroglia may be involved in the synthesis of endogenous neurosteroids. The extension of glial fibrillary acidic protein (GFAP)-immunoreactive astroglial cell processes was assessed in hippocampal slice cultures from adult gonadectomized male rats under the influence of the neurosteroids dehydroepiandrosterone, dehydroepiandrosterone sulfate, dehydroepiandrosterone estereate, pregnenolone, pregnenolone sulfate, and pregnenolone oleate. The effects of neurosteroids were compared to those induced by the gonadal steroids testosterone, 17ß-estradiol and progesterone. Astrocytes in hippocampal slice cultures had a morphology that was indistinguishable from that observed in the hippocampus fixed in situ. Castration of adult male rats resulted in a significant decrease in the extension of GFAP-immunoreactive processes, both in tissues fixed in situ and in slice cultures. In contrast, incubation of slice cultures from gonadectomized animals with pregnenolone, pregnenolone sulfate, 17ß-estradiol, and testosterone enhanced the extension of GFAP-immunoreactive processes. While other steroids tested did not affect this parameter, dehydroepiandrosterone and its sulfate and estereate derivatives induced the transformation of astroglial cells into hypertrophic and highly GFAP immunoreactive cells with the morphological characteristics of reactive astroglia. We conclude that neurosteroids regulate the morphology and/or GFAP distribution of astrocytes in hippocampal slice cultures from adult rats. © 1995 Wiley-Liss, Inc.     

NG2 cells differentiate into astrocytes in cerebellar slices

NG2-glia are an abundant population of glial cells that have been considered by many to be oligodendrocyte progenitor cells (OPCs). However, growing evidence suggests that NG2-glia may also be capable of differentiating into astrocytes and neurons under certain conditions. Here, we have examined NG2-glia in cerebellar slices, using transgenic mice in which the astroglial marker glial specific protein (GFAP) drives expression of the reporter gene enhanced green fluorescent protein (EGFP). Immunolabelling for NG2 shows that NG2-glia and GFAP-EGFP astroglia are separate populations in most areas of the brain, although a substantial population of NG2-glia in the pons also express the GFAP-EGFP reporter. In the cerebellum, NG2-glia did not express EGFP, either at postnatal day (P)12 or P29–30. We developed an organotypic culture of P12 cerebellar slices that maintain cytoarchitectural integrity of Purkinje neurons and Bergmann glia. In these cultures, BrdU labelling indicates that the majority of NG2-glia enter the cell cycle within 2 days in vitro (DIV), suggesting that NG2-glia undergo a ‘reactive’ response in cerebellar cultures. After 2 DIV NG2-glia began to express the astroglial reporter EGFP and in some cases the respective GFAP protein. However, NG2-glia did not acquire phenotypic markers of neural stem cells or neurons. The results suggest that NG2-glia are not lineage restricted OPCs and are a potential source of astrocytes in the cerebellum.     

Studies on the encephalitogenic effects of purified preparations of human and bovine oligodendrocytes.

Bulk-isolated human and bovine oligodendroglia, practically free from myelin, have been used in attempts to elicit an autoimmune response which has been compared with acute experimental allergic encephalomyelitis (EAE). For these experiments, a total of 20 Hartley guinea pigs, 33 Lewis rats and 16 rabbits have been studied. Animals were inoculated with a range of doses of purified preparations of both human and bovine oligodendroglial cells in complete Freund's adjuvant (CFA) and compared with others challenged with whole white matter in CFA. The latter animals all developed clinical and histological signs of experimental allergic encephalomyelitis (EAE) 2-3 weeks post-inoculation. In general, oligodendroglial cells were encephalitogenically less potent than white matter. Guinea pigs were the most susceptible to inoculations of oligodendroglia. In several given human oligodendroglia 14 days earlier, a paraparesis indistinguishable from conventional EAE was seen. Animals receiving bovine cells showed no clinical signs. Histologically, the CNS of afflicted guinea pigs displayed severe inflammation but, in contrast to conventional EAE in the same species, demyelination was rare in the small group of animals tested. After sensitization with oligodendroglia, rats displayed no clinical disease. Histologically, some given human cells had positive evidence of disease while bovine cells in others gave a mild response. Rabbits showed no clinical and very little histological disease. Although more extensive studies are needed to confirm the findings, from the animals studied it appears that (1) variation in response to inocula containing oligodendroglia exists among the species tested, (2) that human oligodendroglia are more potent immunologically than bovine cells, (3) that CNS lesions produced by these cells in guinea pigs, lack a strong demyelinative component and (4) a specific antigen might exist in oligodendrocytes which is distinct from myelin basic protein. The possible reasons underlying our findings are discussed.     

Immunocytochemical localization of Border Disease virus in the spinal cord of fetal and newborn lambs

The peroxidase-antiperoxidase technique was used to determine the cellular localization of Border Disease (BD) virus in cryostat sections of fetal and newborn lamb spinal cord following experimental infection by maternal inoculation in early gestation. Viraemic fetuses and lambs with hypomyelinogenesis showed BD viral antigen in neurons, glia, ependymal cells, vascular endothelial cells and fibrocytes within the dura mater. Double immunolabelling demonstrated co-expression of BD viral antigen and glial fibrillary acidic protein (GFAP) or myelin basic protein (MBP) in both fetal and newborn lamb glia. In fetal lambs there was a pia-associated population of glia in which viral antigen was also co-expressed with GFAP or MBP. The results suggest that BD virus infects myelinating oligodendroglia, astroglia and probably also transitional cells and pluripotential glioblasts. The relationship between infection of specific cell types and hypomyelinogenesis was not resolved but infection of transitional cells and oligodendroglia may affect oligodendroglial function and permit morphologically inapparent perturbations leading to hypomyelinogenesis. A single nonviraemic lamb with a precolostral antibody titre to BD virus and cystic cerebral cavities but no hypomyelinogenesis showed BD viral antigen confined to glia of the spinal cord white matter. This suggests that oligodendroglia may require to be infected before a critical period in their development or factors additional to oligodendroglia infection are necessary for hypomyelinogenesis.     

Distribution of mitochondrial manganese superoxide dismutase among rat glial cells in culture

Enzymatic antioxidant defense systems, like superoxide dismutase (SOD), may protect neuronal and glial cells from reactive oxygen species (ROS) damage. Beside the cytosolic constitutive CuZn SOD, mitochondrial manganese SOD (Mn SOD) represents a ROS inducible enzyme which should allow the adaptation of brain cells to variation in ROS concentrations resulting from their oxidative metabolism. Using immunocytochemistry, the distribution of Mn SOD among the various representatives of the rat brain glial population (astroglia and microglia in primary culture as well as oligodendroglia in secondary culture) has been examined. Among astroglial cells, only a population of flat polygonal-shaped astrocytes, highly immunostained for glial fibrillary acid protein (GFAP) express Mn SOD immunoreactivity. Microglial cells defined by their shape and OX-42 immunoreactivity also express an intense Mn SOD signal. Exposure of the primary culture to reactive oxygen species generated by a xanthine/xanthine oxidase mixture (X/XO) accentuates the Mn SOD signal in astroglial and microglial cells. On the contrary, oligodendroglial cells grown in secondary culture in a serum-free chemically defined or a serum-containing medium and well characterized by their 2′,3′-cyclic nucleotide 3′-phosphodiesterase (CNPase) immunoreactivity never express any immunostaining for Mn SOD, even in response to an extracellular reactive oxygen species generating source like X/XO. Likewise, a population of A2B5-positive glial cells which may represent bipotential O-2A progenitor precursors does not express Mn SOD immunostaining. These results point out that in addition to the well known ability of microglial and astroglial cells to secrete ROS, they also express a high mitochondrial oxygen superoxide decomposition potential. On the contrary, the absence of any observable Mn SOD signal in precursors and in more differentiated oligodendroglial cells could be related to their great sensitivity to ROS damage and could therefore play an important role in the development of various dysmyelinating disorders. GLIA 22:408–414, 1998. © 1998 Wiley-Liss, Inc.     

Remote astrocytic response as demonstrated by glial fibrillary acidic protein immunohistochemistry in the visual cortex of dorsal lateral geniculate nucleus lesioned rats

The reaction of astroglia was investigated after unilateral destruction of the dorsal lateral geniculate nucleus in the primary visual cortex of adult albino rats. The destruction of the dorsal lateral geniculate nucleus was performed by stereotaxic injections of ibotenic acid, and the location was verified in Nissl stained sections in each animal. Electron microscopic observations demonstrated the presence of degenerating axon terminals surrounded by hypertrophic astroglial processes mainly in layers III and IV of the ipsilateral primary visual cortex. The ipsilateral (impaired) and contralateral (control) sides of the primary visual cortex showed light microscopically a clearly differing appearance and distribution of glial fibrillary acidic protein (GFAP) immunoreactivity 7 to 11 days after the unilateral injection of ibotenic acid into the dorsal lateral geniculate nucleus. Whereas the control side of the primary visual cortex showed GFAP staining only in the subpial zone of layer I and close to the white matter, all layers of the impaired cortex showed an intense GFAP immunoreactivity. The increase in immunoreactivity was confined to the primary visual cortex. The extent of and increase in immunoreactivity was corroborated by image analysis. These findings were interpreted as a localized hypertrophy of astroglia caused by the anterograde degeneration of geniculocortical terminals. This hypertrophy is accompanied by an increase in GFAP, which may represent the stabilization of the cytoskeleton of newly formed glial processes involved in the rearrangement of the impaired neuropil.     

An immunocytochemical comparison of the glia-associated proteins glial fibrillary acidic protein (GFAP) and S-100 protein (S100P) in human brain tumors

Immunostaining patterns of two glia-associated proteins, glial fibrillary acidic protein (GFAP) and S-100 protein (S100P), were compared using the peroxidase-antiperoxidase (PAP) method on adjacent paraffin sections in 100 brain tumors including 52 astroglial tumors, 13 oligodendrogliomas, 14 ependymomas, 13 choroid plexus papillomas and 8 medulloblastomas. Most astroglial tumors showed similar immunoreactivity for both proteins. Fibrillary processes, however, showed a stronger and more crisp staining with anti-GFAP than with anti-S100P, whereas cell nuclei were labeled only for S100P. Focal dissociation of immunoreactivities for the two proteins was prominent in several malignant astroglial tumors including giant cell glioblastoma, and in subependymal giant cell astrocytoma. In oligodendrogliomas, GFAP-positive neoplastic oligodendrocytes also showed immunoreactivity for S100P; a smaller number of tumor cells were immunoreactive only for S100P, comparable to normal mature oligodendroglia. Most ependymomas were characterized by a similar distribution of cells immunoreactive for both proteins. In choroid plexus papilloma, absent or only focal immunoreactivity for GFAP contrasted with diffuse labeling for S100P in all cases; this seems of value for a differential diagnosis of papillary CNS tumors. In medulloblastoma, some tumor cells of a classical type were immunoreactive only for S100P; on the contrary, GFAP positive tumor cells with sparse or absent immunoreactivity for S100P were found in desmoplastic medulloblastomas. Similar immunoreactivities for both proteins in most tumors suggest a generally parallel production of both proteins by glial tumor cells.(ABSTRACT TRUNCATED AT 250 WORDS)     

Changes in glial cell markers in recent and old demyelinated lesions in central pontine myelinolysis

Summary An immunohistochemical study was performed to compare glial reactions in recent and old lesions of central pontine myelinolysis (CPM). Regions of demyelination and destruction of oligodendrocytes, showed reduced immunoreactivity of myelin basic protein (MBP), myelin-associated glycoprotein (MAG), transferrin, and carbonic anhydrase C (CA C). In addition, labeling of glial fibrillary acidic protein (GFAP) and S-100 protein revealed distinct dystrophic alterations of the astroglia. Remarkably, immunolabeling of GFAP was drastically reduced in astrocytic cytoplasm within freshly demyelinated lesions. Immunostaining of vimentin revealed a differential intracytoplasmic decoration of hypertrophic and dystrophic astrocytes in recent and old CPM lesions. Immunolabeling of desmin failed to stain glial cells. Monoclonal antibodies against HNK-1 exhibited greatly increased immunoreactivity both of persisting oligodendrocytes and of reactive fibrillary astrocytes in old CPM foci. In freshly demyelinated lesions, enhanced immunoreactivity of the X-hapten (3-fucosyl-N-acetyllactosamine) was prominent in astroglia and oligodendrocytes. Simultaneously, reactive astrocytes revealed intracytoplasmic labeling of laminin. Quantitation of GFAP⁺ astroglia in fresh CPM and control cases revealed an increase in the number of astrocytes within the demyelinated foci and in the surrounding nondemyelinated pontine tissue of CPM cases. The occurrence of astroglial alterations in the demyelinated foci of CPM could be interpreted as astroglial dystrophy which may represent a pathogenic factor in CPM. Furthermore, it is possible that changes of the glial microenvironment may influence the astroglia to revert transiently back to an immature phenotype as indicated by the enhanced expression of the X-hapten and HNK-1, and the de novo synthesis of vimentin and laminin.The Heinrich-Pette-Institut is financially supported by Freie und Hansestadt Hamburg and Bundesministerium für Jugend, Familie, Frauen und Gesundheit     

Ovarian cycle-related changes of glial fibrillary acidic protein (GFAP) immunoreactivity in the rat interpeduncular nucleus

The interpeduncular nucleus (IPN) of female rats was studied across the estrous cycle to observe whether the expression of the astroglial marker, glial fibrillary acidic protein (GFAP) reacts to hormonal changes in an area not belonging to the 'endocrine brain'. A marked reduction of immunoreactive GFAP was observed in estrus as compared to the immunoreactivities in met- and proestrus. This finding is consistent with earlier observations in the endocrine hypothalamus, but also proves that gonadal steroids influence astroglia in brain regions not involved in neuroendocrine regulation. Since cyclic fluctuations of synaptic numbers in the female have been described only for the endocrine hypothalamus, decrease of immunoreactive GFAP in the IPN during estrus may reflect a down-regulation of GFAP synthesis.     

Glial proteins in canine distemper virus-induced demyelination

A temporal series of demyelinating lesions in experimental canine distemper virus (CDV) infection was examined with immunohistological techniques demonstrating myelin basic protein (MBP), myelin-associated glycoprotein (MAG), and glial fibrillary acidic protein (GFAP) on serial sections. The earliest lesions were characterized by decreased MBP and MAG and increased GFAP. During the further progression of the disease, MBP and MAG losses continued to match each other. There was no indication of MAG loss preceding the disappearance of MBP. In the more advanced lesions there was a marked decrease of GFAP positive cells. Since these findings differed considerably from similar immunohistochemical studies in progressive multifocal leukoencephalopathy (PML) where demyelination results from oligodendroglial infection, it was concluded that the oligodendroglial cell body is not the primary target of CDV. The marked astroglial changes were also considered to contribute to demyelination in CDV infection but the mechanism by which this happens remains unknown.     

Neurotrophin-3 (NT-3) diminishes susceptibility of the oligodendroglial lineage to AMPA glutamate receptor-mediated excitotoxicity

Prior reports demonstrated that cells of the oligodendroglial lineage are susceptible to excitotoxic necrosis mediated by alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid glutamate receptors (AMPA-GluR), and also showed that these cells express the high affinity neurotrophin receptors, TrkC and TrkA. We now report that: a) oligodendroglial progenitors (OP) and immature oligodendroglia are more vulnerable to AMPA-GluR-mediated excitotoxicity than are mature oligodendroglia; b) TrkC expression falls substantially during differentiation of cultured OP to mature oligodendroglia, whereas TrkA expression increases markedly; and c) neurotrophin-3, and to a lesser extent, nerve growth factor, protect the oligodendroglial lineage against AMPA-GluR-mediated excitotoxicity.     

Oligodendroglia in developmental neurotoxicity

The developing nervous system has been long recognized as a primary target for a variety of toxicants. To date, most efforts to understand the impact of neurotoxic agents on the brain have focused primarily on neurons and to a lesser degree astroglia as cellular targets. The role of oligodendroglia, the myelin-forming cells in the central nervous system (CNS), in developmental neurotoxicity has been emphasized only in recent years. Oligodendrocytes originate from migratory, mitotic progenitors that mature progressively into postmitotic myelinating cells. During differentiation, oligodendroglial lineage cells pass through a series of distinct phenotypic stages that are characterized by different proliferative capacities and migratory abilities, as well as dramatic changes in morphology with sequential expression of unique developmental markers. In recent years, it has become appreciated that oligodendrocyte lineage cells have important functions other than those related to myelin formation and maintenance, including participation in neuronal survival and development, as well as neurotransmission and synaptic function. Substantial knowledge has accumulated on the control of oligodendroglial survival, migration, proliferation, and differentiation, as well as the cellular and molecular events involved in oligodendroglial development and myelin formation. Recently, studies have been initiated to address the role of oligodendrocyte lineage cells in neurotoxic processes. This article examines recent progress in oligodendroglial biology, focuses attention on the characteristic features of the oligodendrocyte developmental lineage as a model system for neurotoxicological studies, and explores the role of oligodendrocyte lineage cells in developmental neurotoxicity. The potential role of oligodendroglia in environmental lead neurotoxicity is presented to exemplify this thesis.     

Estradiol promotion of changes in the morphology of astroglia growing in culture depends on the expression of polysialic acid of neural membranes

Gonadal steroids are known to affect astroglial morphology in developing and adult animals. Earlier studies of mixed neuronal-glial cultures from fetal rat hypothalamus showed that glial fibrillary acidic protein (GFAP)-immunoreactive cells with a polygonal shape were transformed into process-bearing cells upon exposure to the ovarian hormone estradiol. This effect was dependent on a direct contact of astroglia with living hypothalamic neurons. The present study shows that somata and processes of neurons in such cultures were immunoreactive for polysialic acid (PSA); astroglia were immunonegative. PSA appears to participate in the estradiol-induced shape changes since treatment with endoneuraminidase, an enzyme that specifically removes PSA from the cell surface, abolished PSA immunostaining and prevented the 17ß-estradiol-induced morphological changes of astroglia. In contrast, treatment with endoneuraminidase did not affect astroglial shape changes induced by basic fibroblast growth factor (bFGF), nor those induced by the addition of neurons to glial cultures. These results suggest that PSA on neuronal membranes, probably linked to the highly sialylated isoform of the neural cell adhesion molecule, is necessary for the expression of certain hormonally-regulated neuro-glial interactions. © 1995 Wiley-Liss, Inc.     

Oligodendroglial lineage cells express neuroligand receptors

This study was designed to determine whether cells of the oligodendroglial lineage express neuroligand receptors linked to Ca²⁺ mobilization. Intracellular Ca²⁺ levels were monitored with a video-based imaging system and cells were characterized with immunocytochemical markers. O-2A progenitor cells (A2B5+/GFAP-) and mature oligodendroglia (GC+/MBP+) responded to norepinephrine, glutamate, ATP, and histamine with increased intracellular Ca²⁺ levels. As O-2A progenitor cells differentiated into mature oligodendroglia, there was an increase in the percentage of cells that responded to ATP and histamine with an increase in intracellular Ca²⁺ levels. Both O-2A progenitor cells and mature oligodendroglia were pharmacologically heterogeneous with respect to their ability to respond to neuroligands with an increase in intracellular Ca²⁺. Treatment with bradykinin, carbachol, and substance P also increased intracellular Ca²⁺ levels in O-2A progenitor cells and mature oligodendroglia. Whereas the percentage of cells that responded to bradykinin and substance P increased with differentiation of O-2A progenitor cells into mature oligodendroglia, the trend was reversed with respect to the percentage of cells responding to carbachol. These results suggest that cells of the oligodendroglial lineage exhibit neuroligand receptors linked to Ca²⁺ mobilization and that the ability of these cells to respond to neuroligands is developmentally regulated. © 1993 Wiley-Liss, Inc.