Biomedical subjects

M Gobbi

Publications and source records attributed to M Gobbi.

At least 91 records · Page 5Linked to original sources

PubMed1996

p-Chlorphenylalanine changes serotonin transporter mRNA levels and expression of the gene product.

After a single intraperitoneal injection of the irreversible tryptophan hydroxylase inhibitor p-chlorophenylalanine (PCPA; 300 mg/kg), there was a rapid down-regulation of serotonin (5-HT) transporter mRNA levels in cell bodies. This change was significant at 1 and 2 days after PCPA administration within the ventromedial but not the dorsomedial portion of the dorsal raphe nucleus. Seven days after PCPA treatment, 5-HT transporter mRNA levels were significantly elevated compared with controls in both regions of the dorsal raphe nucleus. PCPA administration produced no change in the [3H]citalopram binding and synaptosomal [3H]5-HT uptake in terminal regions at 2 and 7 days after treatment but significantly reduced both these parameters by approximately 20% in the hippocampus and in cerebral cortex 14 days after PCPA administration. The striatum showed a lower sensitivity to this effect. No significant changes were observed in the levels of [3H]citalopram binding to 5-HT cell bodies in the dorsal raphe nucleus. In the same animals used for 5-HT transporter mRNA level measurements, levels of tryptophan hydroxylase mRNA in neurons of the ventromedial and dorsomedial portions of the dorsal raphe nucleus were increased 2 days after PCPA administration and fell to control levels 7 days after injection in the ventromedial region but not in the dorsomedial portion of the dorsal raphe nucleus, where they remained significantly higher than controls. Altogether, these results show that changes in 5-HT transporter mRNA are not temporally related to changes in 5-HT transporter protein levels. In addition, our results suggest that the 5-HT transporter and tryptophan hydroxylase genes are regulated by different mechanisms. We also provide further evidence that dorsal raphe 5-HT neurons are differentially regulated by drugs, depending on their location.

Animals↗

PubMed1996

FLAG (fludarabine, cytarabine, G-CSF) as a second line therapy for acute lymphoblastic leukemia with myeloid antigen expression: in vitro and in vivo effects.

Thirteen consecutive adult patients with primary refractory (n = 5) or relapsed (n = 8) acute lymphoblastic leukemia (ALL) were treated by an induction schedule (FLAG) consisting of Fludarabine (30 mg/sqm/d) plus high dose Cytarabine (HD-ara-C: 2 g/sqm/d) (d 1-5) and G-CSF (from d O to polymorphonuclear recovery). Patients achieving complete remission (CR) were administered a second FLAG course as consolidation and were then submitted to an individualized program of post-remission therapy, depending on the patient's age and performance status. CR was achieved in 8/12 evaluable cases (67%). The median CR duration was 22.5 w. CR attainment was significantly related to the co-expression of lymphoid and myeloid antigens. ALL/My+ patients achieved CR in 6/6 evaluable cases vs. 2/6 for ALL/My+. In vitro 3H ara-C incorporation into cellular DNA resulted significantly increased by Fludarabine (in 7/9 tested cases) and, furthermore, by the association of Fludarabine G-CSF in 5 evaluable ALL/My+ cases; in contrast, no effect of G-CSF addition to Fludarabine was observed in 4 ALL/My. Myelosuppression was observed in all patients: the median time to neutrophils > 0.5 x 10(9)/1 was 16.3 d (range 13-22) and 16.2 d (range 9-29) to platelets > 20 x 10(9)/1. Nonhematological toxicity was minimal. In conclusion, FLAG is an active and tolerable combination in refractory ALL, particularly in cases with myeloid antigen expression where G-CSF appears to improve efficacy, probably increasing ara-C incorporation into the DNA of leukemic cells.

Adult↗

PubMed1996

Anaplastic large cell lymphoma: a clinicopathologic study of 53 patients.

Fifty-three consecutive cases of adult CD30+ anaplastic large cell lymphoma (ALCL) have been analyzed. Thirty-six were classified as Hodgkin's disease like variety (HL) (67%) and seventeen as so-called common type (CT) (33%). All cases strongly expressed the CD30/Ki-1 antigen; the neoplastic cells expressed CD15, CD45 and EMA in 60%, 44% and 33% of cases, respectively; T. B and null phenotypes were found in 37%, 17% and 46% of cases. Bulky mediastinal, B symptoms, and extranodal disease at diagnosis were present in 36%, 49% and 25% of cases. EBV encoded latent membrane protein (LMP-1) was found in 10 cases. Of the 13 tested cases only 4 expressed a weak positivity of the CD40 molecule, in a fraction of the tumor cells; in the same cases CD21 was never found. Patients were treated with various protocols; of the 50 evaluable patients, 39 (78%) obtained a complete remission (CR), 3 (6%) a partial remission (PR) and 8 (16%) did not respond. The projected overall disease free survival (DFS) at 36 months is 70%. Only patients with advanced disease stage (III-IV) showed a statistically decreased DFS and survival. Only symptomatic and extranodal disease significantly appeared to influence survival. This study confirms the good outcome of this group of lymphomas and differs from other reports for some clinical (lower percentage of advanced stage, extranodal disease and skin infiltration) and pathological (HL/CT ratio and immunophenotype) features.

Adult↗

PubMed1996

Are 5-hydroxytryptamine7 receptors involved in [3H]5-hydroxytryptamine binding to 5-hydroxytryptamine 1nonA-nonB receptors in rat hypothalamus?

We assayed [3H]5-hydroxytryptamine ([3H]5-HT) binding in rat hypothalamic membranes to confirm the possible of measuring 5-HT7 receptors. Binding was tested in the presence of 3 microM (+/-)-pindolol, a concentration higher than previously suggested for the same purpose (0.1 micron). This higher concentration was, however, needed to fully saturate 5-HT1A and 5-HT1B receptors without interaction with 5-HT7 receptors. Under these conditions, [3H]5-HT binding could be further inhibited with methiothepin (used to determine nonspecific binding) and with 5-HT, with an IC50 of 1.4 nM and a slope of 1. The inhibition curves of (+/-)-8-hydroxy-dipropylaminotetralin, ritanserin, and mianserin were shallow (slopes, 0.35-0.58) and could be better analyzed with the two-site model, indicating that the pindolol-insensitive [3H]5-HT binding sites in rat hypothalamic membranes are heterogeneous. Although the IC50 of the compounds tested suggests that one population of sites is actually associated with 5-HT7 receptors, our data clearly indicate that this binding assay does not selectively label 5-HT7 receptors in native tissues. These results challenge a previous report and suggest that the proposed down-regulation of 5-HT7 receptors after fluoxetine treatment should be considered with caution. The development of more selective and sensitive binding assays will probably offer significant advantage.

Animals↗

PubMed1996

Mobilization/transplantation of peripheral blood progenitor cells for aggressive non-Hodgkin's lymphoma with marrow involvement.

Thirty-five aggressive non-Hodgkin's lymphomas (NHL) with marrow involvement received high-dose cyclophosphamide (7 g/m2) and G-CSF in order to collect peripheral blood progenitor cells (PBPC). Fourteen patients were in partial remission, 16 patients were in relapse ('sensitive', 12; 'resistant', 4) and five patients were refractory to conventional treatment. A good yield of PBPC was obtained in 30 patients, while a low number of CD34+ cells and of CFU-GM was seen in two cases. Two patients entered progression and one patient died. Thirty patients underwent PBPC autografting. Twenty-nine out of 35 (83%) patients entered complete remission (CR). Two patients died in CR of infection following marrow aplasia 3 and 6 months after autografting. At 3 years the probability of survival and disease-free survival (DFS) are 62 and 51%, respectively.

Adult↗

PubMed1995

Cardiac disease after chest irradiation for Hodgkin's disease: incidence in 108 patients with long follow-up.

Occult or overt but delayed cardiac disease after thoracic radiotherapy for Hodgkin's disease may be common. Detailed cardiac evaluation was performed in 108 patients, mean age 46 +/- 6.2 years, with Hodgkin's disease at 175 +/- 43 months after irradiation. The study protocol included clinical examination, graded treadmill exercise test and echocardiography. Some patients with angina pectoris, previous myocardial infarction and an abnormal ECG were studied by thallium-201 scintigraphy, cardiac catheterization and coronary angiography. Cardiac disease was found in 12 patients (11%). Three patients had angina pectoris, one patient had myocardial infarction, two complained of dyspnea on effort and two had congestive heart failure. At catheterization, constrictive pericarditis was diagnosed in four patients; in two additional patients an occult constrictive pericarditis was found. One patient had both mitral and tricuspidal regurgitation and one had mitral regurgitation alone. Eight patients (7.4%) had severe coronary artery disease; four of these had associated constrictive pericarditis. Four patients had a pericardiectomy and another four had undergone coronary artery by-pass graft. Two patients died after operation from persistent pericardial constriction. It is concluded that the incidence of delayed cardiac disease after radiotherapy is relatively high; chronic pericardial disorders and coronary artery disease are the most frequent manifestations of this disease. Standard surgical treatment may be beneficial because of the relative youth of these patients.

Adult↗

PubMed1995

Blood toluene as a biological index of environmental toluene exposure in the "normal" population and in occupationally exposed workers immediately after exposure and 16 hours later.

Blood toluene was measured in a group of 100 workers occupationally exposed to a mean 8-h environmental toluene concentration of 128 micrograms/l (34 ppm), and in a group of 269 "normal" subjects without occupational exposure to toluene. The mean blood toluene of the workers at the end of the shift and the following morning, after 16 h, was 457 and 38 micrograms/l, respectively. The normal subjects had a blood toluene level of 1.1 micrograms/l. On the basis of the highly significant correlation between blood toluene and occupational exposure, it can be calculated that environmental toluene exposure of 188 and 377 micrograms/l (50 and 100 ppm) gives end-of-shift blood toluene levels of 690 and 1390 micrograms/l, respectively. The corresponding blood toluene levels on the following morning are 50 and 100 micrograms/l, respectively.

Environmental Exposure↗

PubMed1995

Detection of platelet-associated antibodies by flow cytometry in hematological autoimmune disorders.

We describe our experience in the evaluation of platelet-associated immunoglobulins (PAIg) by flow cytometry in comparison to solid-phase assay in patients affected by idiopathic thrombocytopenic purpura and by Evans syndrome. Results show that the analysis of PAIg by flow cytometry is easy and reliable and correlates well with data obtained by the solid-phase technique. In addition, flow cytometry allows the evaluation of samples containing small numbers of platelets (< 20,000/mm3); the analysis is objective, not influenced by personal experience. Moreover, flow cytometry appears simple enough to be performed in a routine laboratory, and data might be retrieved to perform batch analysis. Our results appear to indicate that PAIg flow cytometry might be a sensitive tool for the evaluation of patients with autoimmune thrombocytopenia.

Autoantibodies↗

PubMed1995

Effects of fluoxetine on basal and K(+)-induced tritium release from synaptosomes preloaded with [3H]serotonin.

Synaptosomes from rat brain cortex and spinal cord were preloaded with [3H]serotonin ([3H]5-HT), superfused and exposed to fluoxetine and/or 15 mM K+. In both regions 10 microM, but not 1 microM fluoxetine evoked a marked tritium overflow, about 2 min later than the immediate [3H]5-HT release induced by K+, and mainly (73%) due to the efflux of a tritiated metabolite of 5-HT, possibly [3H]5-hydroxy-indoleacetic acid. These findings confirm previous data in the rat hippocampus and are probably due to fluoxetine interacting with the 5-HT storage vesicles. One microM fluoxetine significantly reduced the d-fenfluramine-induced [3H]5-HT overflow, in accordance with its action as 5-HT uptake blocker, but did not affect the K(+)-induced [3H]5-HT overflow. This latter finding does not confirm that fluoxetine inhibits the depolarization-induced Ca(2+)-influx, suggested to involve a drug interaction with the L-type Ca(2+)-channels. Thus, the overflow induced by 10 microM fluoxetine was additive with the depolarization-induced overflow, when the two stimuli were applied together. When 10 microM fluoxetine was added 7 min before 15 mM K+, there was no depolarization-induced overflow. Such inhibition might be only apparent and due either to the fluoxetine-induced loss of vesicular 5-HT or to a fluoxetine-induced alterations of synaptic vesicles. The in vivo relevance of the fluoxetine releasing effect remains to be assessed.

Animals↗

PubMed1995

Four-step high-dose sequential chemotherapy with double hematopoietic progenitor-cell rescue for metastatic breast cancer.

PURPOSE: High-dose chemotherapy produces high complete remission (CR) rates and some survival advantage in patients with metastatic breast cancer (BC). A current issue is the possibility that these patients may have an even better prognosis with multiple high-dose treatments. In this study, we evaluated the feasibility of a four-step, high-dose sequential chemotherapy (HDSC) with double autologous hematopoietic progenitor-cell rescue. We also tested the hypothesis that peripheral-blood progenitor cells (PBPCs) harvested following a single recruitment with cyclophosphamide (CY) and granulocyte-macrophage colony-stimulating factor (GM-CSF) allow the safe administration of the whole HDSC with closely timed repeated courses of several non-cross-resistant agents. PATIENTS AND METHODS: The treatment plan included CY 7 g/m2, followed by GM-CSF 5 to 7 micrograms/kg/d administered by continuous intravenous (i.v.) infusion on days 2 to 14; PBPCs with or without bone marrow (BM) harvest; mitoxantrone (NOV) 60, 75, or 90 mg/m2 plus melphalan (L-PAM) 140 to 180 mg/m2 with hematopoietic rescue; methotrexate (MTX) 8 g/m2 plus vincristine (VCR) 1.4 mg/m2; and etoposide (VP-16) 1.5 g/m2 plus carboplatin (PP) 1.5 g/m2 with hematopoietic rescue. RESULTS: All 15 patients enrolled completed the entire treatment and there were no toxic deaths. Hematologic reconstitution was good at each step. The median number of days with an absolute neutrophil count (ANC) less than 100/microL and platelet count less than 20,000/microL were 8 and 3, respectively, after NOV plus L-PAM, and 7 and 4, respectively, after VP-16 plus PP. The main non-hematologic toxicity was mucositis, while organ toxicity was mild and reversible. CONCLUSION: This regimen is feasible, with acceptable toxicity. GM-CSF and PBPCs have a pivotal role, as they hasten hematologic reconstitution, abate toxicity, and allow rapid recycling.

Adult↗

PubMed1995

Cytogenetic clonality in chronic myelomonocytic leukemia studied with fluorescence in situ hybridization.

Chronic myelomonocytic leukemia (CMML) is a myelodysplastic syndrome (MDS) subtype, characterized by monocytosis, dysgranulocytosis and a low number of blast cells in the peripheral blood (PB). The clonal nature of MDS has been demonstrated by various techniques: the stem cell involved initially is capable of myeloid and lymphoid differentiation. Fluorescent in situ hybridization (FISH) is a technique which can be utilized without any pretreatment on whole interphase cells. In this study leukocytes of PB Wright-stained smears from four CMML patients with trisomy 8 (three cases) and 9 (one case) have been analyzed by FISH. Utilizing a probe for the centromere of chromosome 8 and for the heterochromatic region of chromosome 9, we observed the cells involved by trisomy. In each of the four cases neutrophils, eosinophils, basophils and monocytes may show trisomy 8 or 9, whereas lymphocytes resulted disomic. The comparison between leukocytes morphology and genotype suggests that the supernumerary chromosome does not influence cellular differentiation and maturation. We conclude that FISH analysis of PB leukocytes of patients with CMML is informative when studying the clonality of the disease. Chromosomal abnormalities seem to involve a hematopoietic cell committed to myeloid but not lymphoid differentiation. Trisomies 8 and 9 seem to confer some proliferative advantage without influencing the morphologic characteristics of leukocytes. Other causes will be investigated to explain dysmorphisms of neutrophils and monocytes typical of this disease.

Aged↗

PubMed1994

Involvement of P-type Ca2+ channels in the K(+)- and d-fenfluramine-induced [3H]5-HT release from rat hippocampal synaptosomes.

The Ca2(+)-dependent [3H]5-HT release induced by depolarization or by 0.5 microM d-fenfluramine in rat hippocampal synaptosomes, was significantly reduced (35-42%) by three different P-type Ca2+ channels blockers (omega-Agatoxin-IVA, 100 nM, funnel-web spider toxin, FTX, 0.05 microliters/ml, and its synthetic analogue, sFTX, 1 mM), indicating the major role of these channels in the Ca2+ influx preceding neurotransmitter release.

Animals↗

PubMed1994

Differential effects of 5,7-dihydroxytryptamine-induced serotoninergic degeneration of 5-HT1A receptors and 5-HT uptake sites in the rat brain.

The time-course of 5,7-dihydroxytryptamine-induced lesions (2, 5 and 14 days after i.c.v. injection of 150 micrograms) and the effects of acute reserpine treatment (10 mg/kg, i.p., one or 5 days before scheduled death), were evaluated by autoradiography of [3H]paroxetine binding sites in the rat brain. Reserpine had no significant effect on [3H]paroxetine binding, indicating that the depletion of serotonin is not sufficient per se to alter the serotonin uptake sites in any region. Two days after the 5,7-dihydroxytryptamine lesion, [3H]paroxetine binding was already decreased in the majority of brain regions. In the caudate putamen these binding sites were significantly decreased only 14 days after the lesion, whereas the ventral tegmental area (or the enclosed median forebrain bundle), the dorsal raphe (mainly the ventral portion) and the median raphe maintained their high density of serotonin uptake sites even after 14 days. Results were similar using [3H]citalopram as ligand for the serotonin uptake sites, in the brains of rats lesioned 5 days before death; an exception was the ventral portion of the dorsal raphe, where there was a significant increase with [3H]paroxetine and a decrease with [3H]citalopram binding. In adjacent sections of the same brains we also measured [3H]8-OH-DPAT binding, confirming that it completely disappears in the dorsal raphe after the lesion. Thus, considering the extent of serotonin cell body degeneration, there appears to be a paradoxical mismatch between the excessive loss of [3H]8-OH-DPAT binding and the resistance of [3H]citalopram or [3H]paroxetine binding in the dorsal raphe, suggesting that the two binding sites may undergo adaptive regulation in surviving neurons.

5,7-Dihydroxytryptamine↗

PubMed1994

[Comparison between transthoracic and transesophageal echocardiography in the evaluation of candidates to percutaneous mitral valvuloplasty].

The analysis of valvular morphology is important in selecting patients with mitral rheumatic stenosis for percutaneous mitral valvuloplasty. Transthoracic echocardiography definitely plays a major role in this characterization whereas the usefulness of transesophageal echocardiography has not been determined yet. We studied 95 patients (82 females, 13 males, mean age 51 +/- 12 years) undergoing mitral valvuloplasty (Inoue's technique). The two methods were compared for: morphologic mitral score; correlation between score and increase in mitral valve area; ability to predict post valvuloplasty mitral regurgitation; accuracy in detecting atrial thrombosis. A significant linear correlation between transthoracic and transesophageal echocardiographic scores was observed (r = 0.78, p < 0.001). Transesophageal echocardiographic score was significantly lower (6.8 +/- 1.62 versus 7.17 +/- 1.69, p < 0.05) due to a lower estimation of the extent of calcifications (0.7 +/- 0.97 versus 1 +/- 1.12, p < 0.05). Correlation coefficients between increase in mitral valve area and scores obtained with the two methods were similar (0.29 and 0.30). For both echocardiographic techniques 6 was the best cut-off score value. None of the clinical, hemodynamic and echocardiographic variables was able to predict the occurrence of severe mitral regurgitation. Five patients with atrial thrombosis were identified by transesophageal echocardiography but only 1 by transthoracic echocardiography. We conclude that the two echocardiographic methods have complementary roles in the evaluation of patients undergoing mitral balloon valvuloplasty. Mitral valve morphologic score can generally be assessed adequately by transthoracic echocardiography but transesophageal echocardiography is mandatory in order to exclude left atrial thrombi. The occurrence of post valvuloplasty severe mitral regurgitation cannot be reasonably predicted on echocardiographic basis.

Adult↗

PubMed1994

beta-Carotene storage in rat organs following carrier mediated supplementation.

One rat group was supplemented with beta-carotene (BC) both in beadlets and the crystalline form in arachidic oil as a carrier added to standard diet; another rat group was given 1 ml crystalline BC-arachidic oil by gavage twice a week. In both rat groups, each rat ingested 350 mg BC/week for 12 weeks. The animals were then sacrificed and BC levels together with retinyl palmitate presence were assessed by HPLC analysis in liver, lung, kidney, small intestine, mesenteric fat, brain, spleen, stomach and blood plasma. In the first group, high BC storage, ranging from 4.2 to 45.2 nmols/g wet tissue, was found in liver, small intestine, spleen; lesser BC levels were found in lung, kidney, stomach, blood serum; retinyl palmitate was found in liver and lung. In the second group BC levels ranging from 0.5 up to 5,763 nmols/g wet tissue were detected in all organs, except for brain and stomach; the highest levels were in the lung; retinyl palmitate was detected in liver. The lung appeared to be a target organ for BC, as confirmed by its presence in the lungs of control rats fed standard diet and given 1 ml of arachidic oil alone by gavage twice a week.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1993

Acute noise stress reduces [3H]5-hydroxytryptamine uptake in rat brain synaptosomes: protective effects of buspirone and tianeptine.

Acute noise stress decreased [3H]5-hydroxytryptamine ([3H]5-HT) uptake in synaptosomes from rat hypothalamus, hippocampus and cerebral cortex. The decrease was due to the maximum rate of [3H]5-HT uptake, which peaked 30 min after stress and partly returned to resting values within 4 h, with no changes in affinity (Km values). No changes in [3H]paroxetine binding and basal [3H]5-HT release were found in stressed rats. Tianeptine, given at the dose of 10 mg/kg 1 h before stress, counteracted the noise-induced decrease of 5-HT uptake, since it increased [3H]5-HT uptake in both resting and stressed animals, but did not prevent the rise in plasma corticosterone of stressed rats. Buspirone pretreatment had no effect on [3H]5-HT uptake in resting rats but prevented the noise-induced decrease in [3H]-HT uptake. Diazepam did not modify either the basal or the noise-induced reduction in [3H]5-HT uptake. The evidence that treatments reducing extrasynaptic 5-HT, by increasing its reuptake (tianeptine) or reducing its release (buspirone) in innervated regions are able to modify the stress-induced decrease in 5-HT uptake, further confirms the importance of serotonin in the mechanisms mediating neurochemical responses to stress.

Analysis of Variance↗

PubMed1993

Phenotypic analysis of hairy cell leukemia: "variant" cases express the interleukin-2 receptor beta chain, but not the alpha chain (CD25).

Hairy cell leukemia (HCL) is a B-cell chronic lymphoproliferative disorder in which the pathologic cells show a strong expression of CD25 (interleukin-2 [IL-2] receptor alpha chain or p55). "Variant" cases of HCL, characterized by hyperleukocytosis, neoplastic elements with a prominent nucleolus and a higher nucleo/cytoplasmic ratio, and an easily obtained bone marrow aspirate, lack surface CD25 determinants. Limited information is available on the expression of the IL-2 receptor beta chain (p75) on normal and neoplastic B cells. In this study, we have assessed by immunofluorescence and mRNA analysis the presence of the IL-2 receptor alpha and beta chains on 12 cases of classic HCL, as well as on 3 variant cases. The results obtained show that, while the alpha chain of the IL-2 receptor is present only on classic HCL, the IL-2 receptor beta chain (p75) is expressed on both the classic and variant form. Unlike hairy cells, only 8 of the 15 B-cell chronic lymphocytic leukemia cases tested showed a weak expression of the p75 antigen on a small proportion of cells. Purified B lymphocytes from normal healthy controls, as well as Epstein-Barr virus-transformed lymphoblastoid cell lines, showed a weak staining for the p75 determinant, while being CD25-. The results of this study suggest that the expression of the alpha and beta chains of the IL-2 receptor appears to be upregulated or downregulated during the process of B-cell-lineage activation and differentiation.

Adult↗

PubMed1993

Evidence of an exocytotic-like release of [3H]5-hydroxytryptamine induced by d-fenfluramine in rat hippocampal synaptosomes.

The monoamine releasing activity of d-fenfluramine was investigated with an in vitro model consisting of synaptosomes preloaded with the 3H-neurotransmitter and extensively washed in a superfusion apparatus before a 3-min exposure to d-fenfluramine. With this model, the drug-induced release is real and is not confused by inhibition of reuptake by the drug. d-Fenfluramine (0.5 microM) induced only [3H]5-hydroxytryptamine ([3H]5-HT) release from hippocampal synaptosomes whereas 10 microM also induced some overflow from hippocampal synaptosomes preloaded with [3H]noradrenaline or from striatal synaptosomes preloaded with [3H]dopamine, although the overflow was much lower than from 5-HTergic synaptosomes. We then focused on the [3H]5-HT release induced by 0.5 microM d-fenfluramine, which was previously shown to be Ca2+ dependent. The same finding was confirmed in the present study with other experimental protocols, indicating the requirement for extracellular Ca2+ ions. By measuring [3H]5-HT uptake into rat hippocampal synaptosomes we confirmed that Ca(2+)-ions are not required for the function of the 5-HT uptake carrier or for its interaction with d-fenfluramine. d-Fenfluramine-induced [3H]5-HT release was not altered by 1 microM nitrendipine (blocking the L-type Ca2+ channels) but was slightly decreased (20%) by 0.5 microM omega-conotoxin (blocking the N-type Ca2+ channels). It was also inhibited by 0.5 microM clonidine, interacting with alpha 2-adrenergic heteroreceptors, and by 10 nM tetanus toxin, known to affect the exocytosis of different neurotransmitters including 5-HT. These compounds had very similar effects on the Ca(2+)-dependent, exocytotic release of [3H]5-HT induced by depolarization, i.e. by 15 mM K+.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗