Search PubMed⌕ Search

Biomedical subjects

P Marin

Publications and source records attributed to P Marin.

At least 55 records · Page 3Linked to original sources
PubMed1994

Glial receptors and their intervention in astrocyto-astrocytic and astrocyto-neuronal interactions.

As shown on cultured astrocytes from the mouse, in the presence of adenosine deaminase, 2-chloroadenosine by acting on A1-adenosine receptors potentiated the activation of phospholipase C induced by the alpha 1-adrenergic agonist, methoxamine. This potentiation required the presence of external calcium and was blocked by pertussis toxin. Moreover, this potentiation resulted from a cascade of events: activation (by calcium and protein kinase C) of a phospholipase A2 coupled to A1-adenosine receptors, release of arachidonic acid, which inhibited the reuptake of glutamate into astrocytes and finally additional activation of phospholipase C by externally accumulated glutamate through metabotropic receptors. The effects of 2-chloroadenosine and methoxamine were respectively mimicked by somatostatin and substance P while endothelins reproduced the combined effects of 2-chloroadenosine and methoxamine. Conditioned media from treated astrocytes enriched in glutamate stimulated phospholipase C in cultured striatal neurones. In addition, glutamate alone was also found to stimulate phospholipase A2 in astrocytes through receptors exhibiting a pharmacological profile distinct from metabotropic receptors coupled to phospholipase C and the glutamate response was potentiated by ATP. Moreover, the neuronal arachidonic acid production evoked by glutamate was potentiated by acetylcholine. Finally, the combined application of 2-chloroadenosine and methoxamine on striatal astrocytes reduced the permeability of gap junctions between astrocytes and this response was mimicked by arachidonic acid. Together, these results emphasized the contribution of astrocytes in the regulation of glutamatergic transmission.

2-Chloroadenosine↗
PubMed1994

Low-grade lymphoma: clinical and prognostic studies in a series of 143 patients from a single institution.

Clinical and prognostic studies were carried out in a series of 143 patients with low-grade (small-lymphocytic, follicular small cleaved cell, follicular mixed small- and large-cell) lymphoma. After treatment with alkylating agents (21.5% cases), combination chemotherapy (73.3%) or other therapies (5.2%), complete response (CR) was obtained in 40.7% of cases and partial response (PR) in 43.7%. The stage of the disease was the most important factor for response. With a median follow-up of 6.5 years, 48.0% (95% Cl: 37.5-58.5) of patients were alive 10 years after diagnosis. Among the initial parameters, advanced stage. B-symptoms, poor performance status, nodal involvement > 3 sites, extranodal involvement > or = 2 sites, WBC count > or = 10 x 10(9)/L, leukemic expression, high serum LDH levels, and bone marrow infiltration were all related to survival; treatment modality, however, had no influence on survival. In the multivariate analysis, stage (p = 0.008) and age (p = 0.053) were the most important prognostic factors. When considering response to therapy, both CR (p < 0.001) and PR (p = 0.003) emerged as the most important predictive variables, with only the absence of B-symptoms retaining its prognostic significance (p = 0.014) among the other parameters. In addition, in CR patients the duration of the response (< or = 1 year vs. > 1 year) was the most significant parameter for survival (p < 0.001). Finally, the initial stage (p = 0.011) and the histologic subtype (those patients with follicular mixed lymphoma relapsing less frequently than the others) (p = 0.052) were the only significant factors for relapse.

Adult↗
PubMed1994

Accelerated resensitization of the D1 dopamine receptor-mediated response in cultured cortical and striatal neurons from the rat: respective role of alpha 1-adrenergic and N-methyl-D-aspartate receptors.

As previously shown in vivo, noradrenergic and glutamatergic neurons can regulate the denervation supersensitivity of D1 dopaminergic (DA) receptors in the rat prefrontal cortex and striatum respectively. Therefore, the effects of methoxamine (an alpha 1-adrenergic agonist) and glutamate on the resensitization of D1 DA receptors were investigated in cultured cortical and striatal neurons from the embryonic rat. In the presence of sulpiride and propranolol, DA stimulated the D1 DA receptor-mediated conversion of 3H-adenine into 3H-cAMP in both intact cortical and striatal cells and these responses were markedly desensitized in cells preexposed for 15 min to DA (50 microM). The complete recovery of the D1 DA response was more rapid in striatal (15 min) than in cortical (80 min) neurons. Methoxamine accelerated the resensitization of the D1 response in cortical but not in striatal neurons. The effect of the alpha 1-adrenergic agonist in cortical neurons was blocked by prazosin and chlorethylclonidine. In contrast, glutamate accelerated the resensitization of the D1 response in striatal but not in cortical neurons and the effect observed in striatal neurons was totally blocked by 2-amino-5-phosphonovaleric acid, an NMDA receptor antagonist. Protein kinase C was shown to be involved in the alpha 1-adrenergic-induced resensitization of the cortical D1 response but not in the glutamate-evoked resensitization of the striatal D1 response. Finally, for comparison, similar experiments were performed on beta-adrenergic receptors using isoproterenol (1 microM) as an agonist. Methoxamine did not modify the resensitization of the beta-adrenergic response in cortical neurons, but glutamate accelerated the resensitization of this response in striatal neurons.

2-Amino-5-phosphonovalerate↗
PubMed1994

Different response to recombinant human granulocyte-macrophage colony-stimulating factor in primary and secondary graft failure after bone marrow transplantation.

The efficacy of recombinant human granulocyte-macrophage colony-stimulating factor (rhGM-CSF) in graft failure after bone marrow transplantation (BMT) has been evaluated in 25 patients. rhGM-CSF was administered intravenously at a dose of 5 or 10 micrograms/kg. Fourteen patients (seven allogeneic BMT [allo-BMT], seven autologous BMT [ABMT]) were treated for primary bone marrow failure (no granulocyte recovery after BMT), and 11 cases (all allo-BMT) received rhGM-CSF for secondary bone marrow failure (absolute neutrophil count lower than 0.5 x 10(9)/L after a previously sustained granulocyte recovery). Two allo-BMT and three ABMT patients with primary bone marrow failure achieved a granulocyte response to rhGM-CSF. In contrast, nine patients with primary graft failure did not respond to rhGM-CSF (four ABMT, three HLA-identical T-depleted BMT, one minor mismatch BMT, one unrelated BMT). Ten of 11 allo-BMT patients treated for secondary bone marrow failure attained an ANC higher than 0.5 x 10(9)/L, but most became severely neutropenic again at a median time of 4 weeks. The possible cause triggering graft failure (graft-vs.-host disease [GVHD], cytomegalovirus [CMV] infection) remained unsolved in most of these cases. Actuarial probability of survival of the entire series was 16 +/- 9% at 15 months. The severity of graft failure and the presence of other concomitant complications in most of our patients may justify these poor results. In conclusion, rhGM-CSF had less efficacy in patients with primary bone marrow failure than in those with secondary bone marrow failure. In the latter setting, measures addressed to correct the initial cause of graft failure are mandatory.

Adolescent↗
PubMed1994

Graft rejection and second bone marrow transplants for acquired aplastic anaemia: a report from the Aplastic Anaemia Working Party of the European Bone Marrow Transplant Group.

Six hundred and eighteen patients with acquired aplastic anaemia grafted from an HLA-identical sibling donor between 1976 and 1990 in eight European centres were reported to the Working Party for Severe Aplastic Anaemia (SAA) Registry and were evaluable for analysis of the incidence of graft failure/rejection and the outcome of second bone marrow transplants (BMT). The number of patients experiencing graft rejection declined significantly over the study period from 32% to 8% (p < 0.0001). This coincided with the introduction of cyclosporine to the conditioning regimen for BMT. The graft rejection rate in the post-hepatitis SAA group was significantly lower than in the group with idiopathic SAA (4% vs 20%) (p = 0.001). The use of irradiation in the conditioning regimen significantly reduced the number of patients experiencing graft rejection (7% vs 21%) (p = 0.004). Age, sex and severity of disease did not influence the rate of sustained engraftment. Of the 85 patients experiencing graft rejection, 41 received a second transplant: their survival is 33% vs 8% for patients not transplanted a second time (p = 0.003). The major factor predicting the outcome of second BMT for SAA was the interval from first BMT. Patients receiving a second BMT within 60 days from the first BMT had a significantly poorer outcome.

Adolescent↗
PubMed1993

Depression and immunity: age, severity, and clinical course.

To begin exploring the relationships between immunity and clinical characteristics of depressive disorders and to further investigate the association of Major Depressive Disorder with age- and severity-related alterations in T lymphocyte numbers and in response to mitogens, we investigated 53 untreated adult outpatients with DSM III-R Major Depressive Episode (MDE) and 53 healthy matched controls. The only group difference between MDE patients and matched controls was a trend (p < .06) for a decreased number of NK cells in depressed subject. In the MDE subjects, increasing age was observed to have a significant independent correlation with decreased numbers of total lymphocyte (p < .01), B cells (p < .05), and DR+ cells (p < .05) and reduced phytohemagglutinin (PHA) (p < .01) and concanavalin A (Con A) (p < .05) mitogen responses. In addition, in the depressed subjects there was: (1) an age-independent negative correlation between increased duration of the last Major Depressive Syndrome and PHA (p < .005), Con A (p < .05), and Pokeweed mitogen (p < .01) responses and (2) an age-independent correlation between increased time from the last antidepressant medication and total number of lymphocytes (p < .05), T cells (p < .05), and NK cells (p = .001). All the above were independent of current life habits such as current tobacco, alcohol, and benzodiazepine use. The present study suggests that both age at the time of study and clinical characteristics of the depressive disorder may be important independent factors in understanding psychoimmunological relationships in Major Depression.

Adult↗
PubMed1993

Non-classical glutamate receptors, blocked by both NMDA and non-NMDA antagonists, stimulate nitric oxide production in neurons.

In striatal neurons in primary culture, kainate and domoate stimulated cGMP production, whereas two other analogs of glutamate which act at non-NMDA receptors, alpha-amino-3-hydroxy-5-methyl-isoxazole-4-propionate (AMPA) and quisqualate were ineffective. However, both agonists stimulated cGMP accumulation on neurons pretreated with concanavalin A, a lectin which is known to prevent desensitization of AMPA receptors. We show here that such a treatment also potentiated the kainate-stimulated cGMP production. Responses induced by all agonists of non-NMDA receptors tested were mediated by nitric oxide (NO) production, since they were inhibited by haemoglobin, an NO scavenger, and two competitive inhibitors of NO-synthase L-NG-monomethylarginine and L-NG-nitro-arginine, the effects of both inhibitors being reversed by an excess of L-arginine. The rank order of potency of the agonists tested (domoate > kainate approximately AMPA approximately quisqualate) suggests that a kainate receptor subtype triggers NO production in striatal neurons. Surprisingly, response evoked by maximally effective concentrations of kainate, quisqualate and AMPA on concanavalin A-treated neurons were partially antagonized by two non-competitive antagonists of NMDA receptors, MK-801 and phencyclidine, and by Mg2+ ions, which block NMDA-operated channels. However, in neurons which had not been treated with concanavalin A, kainate-induced NO production was not inhibited by these antagonists. These results suggest that, in addition to kainate receptor subtype, another glutamate receptor subtype which may be composed of both kainate and NMDA receptor subunits and which is desensitized by kainate, AMPA and quisqualate, is involved in NO production.

6-Cyano-7-nitroquinoxaline-2,3-dione↗
PubMed1993

Relapse of aplastic anaemia after immunosuppressive treatment: a report from the European Bone Marrow Transplantation Group SAA Working Party.

This study was designed to determine the incidence of relapse and factors predictive for relapse in 719 patients with severe aplastic anaemia (SAA) after immunosuppressive treatment (IS). Patients developing myelodysplasia or acute leukaemia after IS, and patients receiving a transplant, were excluded from this analysis. Response was defined as reaching complete independence from transfusions, relapse was defined as becoming again transfusion dependent. This criteria was validated by similar figures when using other 'relapse criteria' such as drop in neutrophil or platelet counts. Of 358 patients responding to IS. 74 patients relapsed after a mean time of 778 d after treatment. The actuarial incidence of relapse is 35.2% at 14 years after IS. The risk for relapse was higher in patients responding within 120 d from IS (48%) compared to patients responding between 120 and 360 d (40%) and only 20% for slow responders (> 360 d from IS) (P < 0.00001). In multivariate analysis this factor still proved significant (P < 0.0001). The mean time between diagnosis and treatment was significantly longer in patients relapsing compared to patients who did not relapse (260 v 134 d, P = 0.037). Relapse was not predicted by the severity of the disease, age, and sex. In 39 of the 74 relapsing patients a second response could be achieved. Responses after relapse were associated in univariate analysis with early response to previous IS and early occurrence of relapse. The actuarial survival of patients not relapsing is significantly better than survival of patients relapsing (79.8% v 67.1%, P = 0.0024). However, the actuarial survival of 39 relapsing patients who responded again to IS was similar to patients not relapsing (86%) and significantly better than in 35 patients not reaching a second response after relapse (49.3%, P = 0.0015). This study indicates that relapse is a relevant problem in the treatment of aplastic anaemia, and does have an impact on overall survival. Prospective studies of immunosuppressive regimens, looking at responses, should also address this problem in the future.

Adolescent↗
PubMed1993

Large-cell lymphoma: a study of prognostic factors and assessment of five recently proposed predictive systems.

The main initial and evolutive variables of 133 patients with large-cell lymphoma treated with adriamycin-containing regimens were evaluated for prognostic significance. At the time of analysis, 66 patients had died with the median survival of the series being 48.9 months. Variables associated with poor prognosis in the univariate study were: lymphoma of immunoblastic subtype, advanced Ann Arbor stage, presence of B-symptoms, poor performance status, bulky disease (> or = 10 cm), involvement of two or more extranodal sites, bone marrow infiltration, and high serum LDH levels. In the multivariate analysis, Ann Arbor stage (p < 0.001), bulky disease (p = 0.004), performance status (p = 0.018), and histologic subtype (p = 0.021) retained their prognostic value. After excluding those patients with localized disease (stage I), the Ann Arbor staging system lost prognostic significance in favor of bone marrow infiltration (p = 0.009) and serum LDH (p < 0.001). However, when response to treatment was included in the regression model, it proved to be the most important prognostic factor (p < 0.001), followed by serum LDH (p = 0.004). On the other hand, when the analysis was restricted to complete responders, serum LDH at diagnosis was the only parameter useful to predict survival (p = 0.008). Finally, five recently proposed prognostic classifications were useful to separate different risk-groups of patients when applied to the series.

Aged↗
PubMed1993

Role of arachidonic acid and glutamate in the formation of inositol phosphates induced by noradrenalin in striatal astrocytes.

The noradrenalin-evoked production of [3H]inositol phosphates in mouse striatal astrocytes in primary culture appeared to be the result of the combined stimulation of alpha 1- and alpha 2-adrenergic receptors. Indeed, the noradrenalin (100 microM) response was only partially reproduced by a maximally effective concentration of methoxamine (100 microM), a selective agonist of alpha 1-adrenergic receptors. In addition, the noradrenalin (100 microM)-induced production of [3H]inositol phosphates, which was completely suppressed by the alpha 1-adrenergic antagonist prazosin (1 microM), was also partially inhibited by yohimbine, a selective antagonist of alpha 2-adrenoceptors (maximum inhibition = -57 +/- 11%, measured in the presence of 10 microM yohimbine; six experiments). Finally, UK14.304, a selective alpha 2-adrenergic agonist that was ineffective alone, enhanced the methoxamine-evoked production of [3H] inositol phosphates (EC50 = 86 +/- 21 nM; three experiments). These results suggest that the stimulation of alpha 1-adrenergic receptors is required for the alpha 2-adrenergic receptor-mediated enhancement of phospholipase C activity. The increased production of [3H]inositol phosphates resulting from the stimulation of alpha 2-adrenergic receptors involved pertussis toxin-sensitive G proteins (Gi/o) and depended on extracellular calcium. As shown using the fluorescent dye indo-1, noradrenalin (100 microM) induced a long-lasting increase in cytosolic calcium in striatal astrocytes. Moreover, noradrenalin (100 microM) stimulated [3H]arachidonic acid release from these cells. These two latter responses may result from synergistic effects due to the combined stimulation of alpha 1- and alpha 2-adrenergic receptors, because they were inhibited by either prazosin (1 microM) or yohimbine (10 microM). Finally, the noradrenalin-evoked production of [3H]inositol phosphates seems to result partly from an inhibition by arachidonic acid of glutamate uptake into astrocytes, leading to the stimulation of glutamate metabotropic receptors coupled to phospholipase C. Indeed, the alpha 2-adrenergic component of the noradrenalin response was suppressed by either enzymatic removal of external glutamate or addition of 2-amino-3-phosphonopropionic acid (1 mM), an antagonist of glutamate metabotropic receptors that blocked the glutamate-evoked production of [3H]inositol phosphates in striatal astrocytes, and was reproduced by the direct application of either glutamate or an inhibitor of glutamate uptake, beta-methyl-DL-aspartic acid.

Adrenergic alpha-Agonists↗
PubMed1992

Nitric oxide-induced blockade of NMDA receptors.

We studied the effects of nitric oxide (NO)-producing agents on N-methyl-D-aspartate (NMDA) receptor activation in cultured neurons. 3-Morpholino-sydnonimine (SIN-1) blocked both NMDA-induced currents and the associated increase in intracellular Ca2+. The actions of SIN-1 were reversible and suppressed by hemoglobin. A degraded SIN-1 solution that did not release NO was unable to block NMDA receptors. This showed that the SIN-1 effects were due to NO and not to another breakdown product. Similar results were obtained with 1-nitrosopyrrolidine (an NO-containing drug) and with NO released from NaNO2. Pretreatment with hemoglobin potentiated NMDA-induced effects, demonstrating that endogenous NO modulates NMDA receptors. Since NMDA receptor activation induces NO synthesis, these results suggest a feedback inhibition of NMDA receptors by NO under physiological condition.

Animals↗
PubMed1992

Synergistic regulation of cytosolic Ca2+ concentration by somatostatin and alpha 1-adrenergic agonists in mouse astrocytes.

The effects of somatostatin and alpha 1-adrenergic receptor agonists on cytosolic Ca2+ in striatal astrocytes from the embryonic mouse in primary culture have been investigated by microfluorimetry. Methoxamine or somatostatin induced a transitory increase in cytosolic Ca2+, but their combined addition led to a sustained increase in cytosolic Ca2+ which seems to be due to a Ca2+ influx since it was not observed in the absence of external Ca2+. Voltage-independent Ca2+ channels contribute to this process. Indeed, voltage-operated calcium channels are not involved since neither dihydropyridines nor La3+ were effective in suppressing the sustained cytosolic Ca2+ elevation. Moreover, depolarization by 50 mM KCl, which was ineffective alone, suppressed the effect of somatostatin observed in the presence of the alpha 1 agonist, methoxamine. The implication of arachidonic acid in the observed potentiation is suggested by the following observations: 1) arachidonic acid induced a sustained elevation of cytosolic Ca2+ similar to that evoked by the co-application of methoxamine and somatostatin; 2) the addition of ETYA, an inactive and non-metabolizable analogue of arachidonic acid suppressed the calcium plateau produced by the agonists. In addition, direct activation of PKC by an exogeneous diacylglycerol analogue allowed somatostatin alone to evoke a sustained elevation of cytosolic Ca2+. Therefore, methoxamine through the successive activation of PLC and PKC could allow a lipase, probably PLA2, to be stimulated by somatostatin. Since arachidonic acid has already been shown to trigger the opening of K+ channels and the formation of inositol phosphates, somatostatin, through the arachidonic acid-mediated hyperpolarization could increase the Ca2+ driving force and thus improve Ca2+ influx through the inositol phosphate gated channels.

5,8,11,14-Eicosatetraynoic Acid↗
PubMed1992

2-Chloroadenosine potentiates the alpha 1-adrenergic activation of phospholipase C through a mechanism involving arachidonic acid and glutamate in striatal astrocytes.

In cultured striatal astrocytes, 2-chloroadenosine, an adenosine analog resistant to adenosine deaminase, although inactive alone, markedly potentiated the activation of phospholipase C induced by methoxamine, an alpha 1-adrenergic agonist. This effect was suppressed by antagonists of either A1 adenosine or alpha 1-adrenergic receptors. An influx of calcium and two distinct G-proteins are involved in this phenomenon since the potentiating effect of 2-chloradenosine was suppressed in the absence of external calcium or when cells were pretreated with pertussis toxin. In addition, arachidonic acid is likely involved in this potentiating effect. This was shown first by examining the effects of inhibitors of phospholipase A2 or arachidonic metabolism, then by examining the action of arachidonic acid on the production of inositol phosphates in either the presence or absence of methoxamine, and finally by measuring the release of arachidonic acid. The sequential activation of phospholipase C and of protein kinase C is required for the 2-chloroadenosine-induced activation of phospholipase A2 since 2-chloroadenosine markedly stimulated phospholipase C activity in the absence of methoxamine when protein kinase C was activated by a diacylglycerol analog. Finally, the enhancing effect of 2-chloroadenosine on the methoxamine-evoked response seems to result from an inhibition of glutamate reuptake into astrocytes by arachidonic acid. Indeed, the potentiating effect of 2-chloroadenosine was suppressed when external glutamate was removed enzymatically and mimicked by either selective inhibitors of the glutamate reuptake process or direct application of glutamate.

2-Chloroadenosine↗
PubMed1991

Somatostatin potentiates the alpha 1-adrenergic activation of phospholipase C in striatal astrocytes through a mechanism involving arachidonic acid and glutamate.

As previously shown with adenosine, somatostatin, which is ineffective alone, enhanced the alpha 1-adrenergic-agonist-stimulated production of inositol phosphates in cultured striatal astrocytes. This effect was suppressed in cells pretreated with pertussis toxin. It required external calcium and was selectively antagonized by both mepacrine, an inhibitor of phospholipase A2, and 5,8,11,14-eicosatetraynoic acid, a nonmetabolizable analog of arachidonic acid. In addition, a long-lasting elevation of cytosolic calcium and a release of arachidonic acid were observed only under the combined stimulation of somatostatin and alpha 1-adrenergic receptors. Arachidonic acid could in turn inhibit glutamate uptake into astrocytes, and the resulting external accumulation of glutamate could account for the somatostatin-evoked amplification of the alpha 1-adrenergic-agonist-stimulated hydrolysis of inositol-phospholipids. The effect of somatostatin was indeed reproduced by glutamate or glutamate uptake inhibitors and suppressed by enzymatic removal of external glutamate. Thus, astrocytes may contribute to long-term plasticity events in glutamatergic synapses through regulation of external glutamate levels.

5,8,11,14-Eicosatetraynoic Acid↗
PubMed1991

Adrenergic regulation of intercellular communications between cultured striatal astrocytes from the mouse.

The permeability of gap junctions in cultured striatal astrocytes was investigated by the scrape-loading/dyetransfer technique. Prolonged application of norepinephrine (NE) (10 microM) reduced by half the extent of dye (Lucifer yellow) spread. This effect was linked to the activation of alpha 1-adrenergic receptors since it was mimicked by methoxamine and antagonized by prazosin. The adenosine agonist 2-chloroadenosine (10 microM), which potentiates the NE-evoked activation of phospholipase C (PLC) in striatal astrocytes, also potentiated the NE-evoked closure of gap junctions, the effect being as important as that observed with the uncoupling agent octanol. Measurements of inositol phospholipid turnover performed in identical experimental conditions revealed a close relationship between the extent of PLC activation and the magnitude of the uncoupling process. The effect of NE was mimicked by both phorbol ester and arachidonic acid, suggesting that biochemical events linked to PLC stimulation such as protein kinase C activation and/or eicosanoid production are likely involved in the NE-induced uncoupling. In addition, in the presence of a cAMP phosphodiesterase inhibitor, the stimulation of beta-adrenergic receptors by isoproterenol (10 microM) led to a large increase in cAMP accumulation correlated with an extension of dye diffusion. This observation suggests that junctional permeability could also be controlled by a cAMP-dependent mechanism. Altogether these results indicate that intercellular communication between cultured astrocytes can be regulated by different second messenger pathways as a result of the action of neurotransmitters on their receptors.

Animals↗
PubMed1991

Functional endothelin-1 receptors in rat astrocytoma C6.

Rat astrocytoma C6 cells have been recently identified as target cells for ET-1, which stimulates inositol lipid turnover in these cells. It is shown here that binding of ET-1 to high-affinity receptors on C6 cells leads to 40-45% inhibition of isoproterenol-induced intracellular cyclic AMP accumulation, as well as to stimulation of inositol lipid turnover, both effects characterized by an absolute requirement of extracellular calcium. Moreover, ET-1, which has been generally reported to have a mitogenic effect on a variety of target cells including primary rat astrocytes, is shown here to stimulate or, alternatively, inhibit DNA synthesis in C6 cells, depending on the subclone considered.

Animals↗
PubMed1991

Synergistic effects in the alpha 1- and beta 1-adrenergic regulations of intracellular calcium levels in striatal astrocytes.

1. Using indo-1 as a calcium fluorescent probe, we have observed the following in striatal astrocytes in primary culture. 2. The stimulation of alpha-adrenoceptors induces a rapid rise in cytosolic calcium resulting from an internal calcium mobilization followed by an external calcium influx (4-min duration). 3. The stimulation of beta 1-adrenoceptors evokes only a slight internal calcium mobilization (90-sec duration). 4. The simultaneous stimulation of beta 1- and alpha 1-adrenoceptors induces a more prolonged calcium influx (10 min). The latter phenomenon could explain the calcium-dependent synergistic effects of alpha 1 and beta stimulation on cAMP production already described in the brain.

Albuterol↗