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Brain Synaptosomes (brain + synaptosome)
Kinds of Brain Synaptosomes Selected AbstractsVoltage-dependent ebselen and diorganochalcogenides inhibition of 45Ca2+ influx into brain synaptosomesJOURNAL OF BIOCHEMICAL AND MOLECULAR TOXICOLOGY, Issue 3 2003M. B. Moretto Abstract By mediating the Ca2+ influx, Ca2+ channels play a central role in neurotransmission. Chemical agents that potentially interfere with Ca2+ homeostasis are potential toxic agents. In the present investigation, changes in Ca2+ influx into synaptosomes by organic forms of selenium and tellurium were examined under nondepolarizing and depolarizing conditions induced by high KCl concentration (135 mM) or by 4-aminopyridine (4-AP). Under nondepolarizing conditions, ebselen (400 ,M) increased Ca2+ influx; diphenyl ditelluride (40,400 ,M) decreased Ca2+ in all concentrations tested; and diphenyl diselenide decreased Ca2+ influx at 40 and 100 ,M, but had no effect at 400 ,M. In the presence of KCl as depolarizing agent, ebselen and diphenyl ditelluride decreased Ca2+ influx in a linear fashion. In contrast, diphenyl diselenide did not modify Ca2+ influx into isolated nerve terminals. In the presence of 4-AP (3 mM) as depolarizing agent, ebselen (400 ,M) caused a significant increase, whereas diphenyl diselenide and diphenyl ditelluride inhibited Ca2+ influx into synaptosomes. The results can be explained by the fact that the mechanism through which 4-AP and high K+ induced elevation of intracellular Ca2+ is not exactly coincident. The mechanism by which diphenyl ditelluride and ebselen interact with Ca2+ channel is unknown, but may be related to reactivity with critical sulfhydryl groups in the protein complex. The results of the present study indicate that the effects of organochalcogenides were rather complex depending on the condition and the depolarizing agent used. © 2003 Wiley Periodicals, Inc. J Biochem Mol Toxicol 17:154,160, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/jbt.10073 [source] N,N -dimethyl-thioamphetamine and methyl-thioamphetamine, two non-neurotoxic substrates of 5-HT transporters, have scant in vitro efficacy for the induction of transporter-mediated 5-HT release and currentsJOURNAL OF NEUROCHEMISTRY, Issue 5 2008Marco Gobbi Abstract We studied two non-neurotoxic amphetamine derivatives (methyl-thioamphetamine, MTA and N,N- dimethylMTA, DMMTA) interacting with serotonin (5-HT) transporters (SERTs) with affinities comparable to that of p- Cl-amphetamine (pCA). The rank order for their maximal effects in inducing both [3H]5-HT release from rat brain synaptosomes or hSERT-expressing HEK-293 cells, and currents in hSERT-expressing oocytes, was pCA » MTA , DMMTA. A correlation between drug-induced release and currents is also strengthened by the similar bell shape of the dose,response curves. Release experiments indicated that MTA and DMMTA are SERT substrates although MTA is taken up by HEK-293 cells with a Vmax 40% lower than pCA. The weak effects of MTA and DMMTA in vitro might therefore be due to their properties as ,partial substrates' on the mechanisms, other than translocation, responsible for currents and/or release. After either local or systemic in vivo administration, MTA and DMMTA release 5-HT in a manner comparable to pCA. These findings confirm that the neurotoxic properties of some amphetamine derivatives are independent of their 5-HT-releasing activity in vivo. It is worth noting that only those amphetamine derivatives with high efficiency in inducing 5-HT release and currents in vitro have neurotoxic properties. [source] Evidence of calcium- and SNARE-dependent release of CuZn superoxide dismutase from rat pituitary GH3 cells and synaptosomes in response to depolarizationJOURNAL OF NEUROCHEMISTRY, Issue 3 2007Mariarosaria Santillo Abstract The antioxidant enzyme CuZn superoxide dismutase (SOD1) is secreted by many cell lines. However, it is not clear whether SOD1 secretion is only constitutive or can be regulated in an activity-dependent fashion. Using rat pituitary GH3 cells that express voltage-dependent calcium channels and are subjected to Ca2+ oscillations, we found that treatment with high K+ -induced SOD1 release that was significantly higher than the constitutive secretion. Evoked SOD1 release was correlated with depolarization-dependent calcium influx and was virtually abolished by removal of extracellular calcium with EGTA or by pre-incubation of GH3 cells with Botulinum toxin A that cleaves the SNARE protein SNAP-25. Immunofluorescence experiments performed in GH3 cells and rat brain synaptosomes showed that K+ -depolarization induced a marked depletion of intracellular SOD1 immunoreactivity, an effect that was again abolished in the absence of extracellular calcium or after treatment with Botulinum toxin A. Subcellular fractionation analysis showed that SOD1 was present in large dense core vesicles. These data clearly show that, in addition to the constitutive SOD1 secretion, depolarization induces an additional rapid calcium-dependent SOD1 release in GH3 cells and in rat brain synaptosomes. This likely occurs through exocytosis from SOD1-containing vesicles operated by the SNARE complex. [source] Effectiveness of extracellular lactate/pyruvate for sustaining synaptic vesicle proton gradient generation and vesicular accumulation of GABAJOURNAL OF NEUROCHEMISTRY, Issue 3 2006A. S. Tarasenko Abstract The effects of extracellular monocarboxylates pyruvate and lactate on membrane potentials, acidification and neurotransmitter filling of synaptic vesicles were investigated in experiments with rat brain synaptosomes using [3H]GABA and fluorescent dyes, potential-sensitive rhodamine 6G and pH-sensitive acridine orange. In experiments investigating accumulation of acridine orange in synaptic vesicles within the synaptosomes, monocarboxylates, similarly to glucose, ensured generation of the vesicle proton gradient by available and recycled vesicles, and pyruvate demonstrated the highest efficacy. An increase in the level of proton gradient correlated with enhanced accumulation of [3H]GABA in synaptic vesicles and resulted in enlarged exocytosis and attenuated the transporter-mediated [3H]GABA release. Pyruvate added to glucose-contained medium caused more active binding of rhodamine 6G by synaptosomes that reflected mitochondrial membrane hyperpolarization, and this intensification of nerve terminal energy metabolism resulted in an increase in total ATP content by ,25%. Pyruvate also prolonged the state of metabolic competence of nerve terminal preparations, keeping the mitochondrial potential and synaptic vesicle proton gradient at steady levels over a long period of time. Thus, besides glucose, the extracellular monocarboxylates pyruvate and lactate can provide sufficient support of energy-dependent processes in isolated nerve terminals, allowing effective functioning of neurotransmitter release and reuptake systems. [source] Increased phosphorylation and redistribution of NMDA receptors between synaptic lipid rafts and post-synaptic densities following transient global ischemia in the rat brainJOURNAL OF NEUROCHEMISTRY, Issue 1 2005Shintaro Besshoh Abstract Ischemia results in increased phosphorylation of NMDA receptors. To investigate the possible role of lipid rafts in this increase, lipid rafts and post-synaptic densities (PSDs) were isolated by the extraction of rat brain synaptosomes with Triton X-100 followed by sucrose density gradient centrifugation. Lipid rafts accounted for the majority of PSD-95, whereas SAP102 was predominantly located in PSDs. Between 50 and 60% of NMDA receptors were associated with lipid rafts. Greater than 85,90% of Src and Fyn were present in lipid rafts, whereas Pyk2 was mainly associated with PSDs. Lipid rafts and PSDs were isolated from animals subjected to 15 min of global ischemia followed by 6 h of recovery. Ischemia did not affect the yield, density, flotillin-1 or cholesterol content of lipid rafts. Following ischemia, the phosphorylation of NR1 by protein kinase C and tyrosine phosphorylation of NR2A and NR2B was increased in both lipid rafts and PSDs, with a greater increase in tyrosine phosphorylation occurring in the raft fraction. Following ischemia, NR1, NR2A and NR2B levels were elevated in PSDs and reduced in lipid rafts. The findings are consistent with a model involving close interaction between lipid rafts and PSDs and a role for lipid rafts in ischemia-induced signaling pathways. [source] Effects of oral administration of extracts of Hypericum perforatum (St John's wort) on brain serotonin transporter, serotonin uptake and behaviour in miceJOURNAL OF PHARMACY AND PHARMACOLOGY: AN INTERNATI ONAL JOURNAL OF PHARMACEUTICAL SCIENCE, Issue 12 2004Kazufumi Hirano The pharmacological effects of extracts of Hypericum perforatum (St John's wort) were characterized in-vitro and ex-vivo, in relation to its behavioural effects. In in-vitro experiments, St John's wort inhibited brain synaptosomal [3H]serotonin uptake in mice with little effect on specific [3H]paroxetine binding. For selective serotonin-reuptake inhibitors (SSRIs), the IC50 value for [3H]serotonin uptake (molar concentration of unlabelled drug necessary to displace 50% of specific uptake) correlated well with the inhibition constant Ki value for [3H]paroxetine binding in mouse brain. Oral administration of St John's wort (900 mg kg,1), paroxetine (1 mg kg,1) and sertraline (10 mg kg,1) brought about significant increases in the Km value for [3H]serotonin uptake into brain synaptosomes 4 h later, and only SSRIs suppressed specific [3H]paroxetine binding in mouse brain. St John's wort and SSRIs significantly inhibited marble-burying behaviour in mice and the time-course of attenuation of this behaviour by St John's wort was similar to that of [3H]serotonin uptake inhibition. In the forced swimming test, St John's wort, but not SSRIs, suppressed the immobility time of mice after oral administration. These results provide the first in-vivo evidence to suggest that the mode of antidepressant action of St John's wort differs from that of SSRIs. Thus, this study may have a significant impact on phytotherapy with St John's wort. [source] Binding characteristics of BmK I, an ,-like scorpion neurotoxic polypeptide, on cockroach nerve cord synaptosomesCHEMICAL BIOLOGY & DRUG DESIGN, Issue 4 2000Y.-J. Li Abstract: In this study, the binding characteristics of BmK I, an ,-like neurotoxic polypeptide purified from the venom of the Chinese scorpion Buthus martensi Karsch, were investigated on rat brain and cockroach nerve cord synaptosomes. The results showed that BmK I can bind to a single class of noninteracting binding sites on cockroach nerve cord synaptosomes with medium affinity (Kd = 16.5 ± 4.4 nm) and low binding capacity (Bmax= 1.05 ± 0.23 pmol/mg protein), but lacks specific binding on rat brain synaptosomes. BmK AS, BmK AS-1 (two novel sodium channel-blocking ligands), BmK IT (an excitatory insect-selective toxin) and BmK IT2 (a depressant insect-selective toxin) from the same venom were found to be capable of depressing BmK I binding in cockroach nerve cord synaptosomes, which might be attributed to either allosteric modulation of voltage-gated Na+ channels by these toxic polypeptides or partial overlapping between the receptor binding sites of BmK I and these toxins. This thus supported the notion that ,-like scorpion neurotoxic polypeptides bind to a distinct receptor site on sodium channels, which might be similar to the binding receptor site of ,-type insect toxins, and also related to those of BmK AS type and insect-selective scorpion toxins on insect sodium channels. [source] | ||||||||||