Effects of Antidepressants on γ-Aminobutyric Acid- and N-Methyl-<i>D</i>-Aspartate-Induced Intracellular Ca<sup>2+</sup> Concentration Increases in Primary Cultured Rat Cortical Neurons

The roles of nicotine on Ca2+ oscillations [intracellular Ca2+ ([Ca2+]i) oscillation] in rat primary cultured cortical neurons were studied. The spontaneous [Ca2+]i oscillations (SCO) were recorded in a portion of the neurons (65%) cultured for 7–10 days in vitro. Application of nicotine enhanced [Ca2+]i oscillation frequency and amplitude, which were reduced by the selective α4β2-nicotinic acetylcholine receptors (nAChRs) antagonist dihydro-β-erythroidine (DHβE) hydrobromide, and the selective α7-nAChRs antagonist methyllycaconitine citrate (MLA, 20 nM). DHβE reduced SCO frequency and prevented the nicotinic increase in the frequency. DHβE somewhat enhanced SCO amplitude and prevented nicotinic increase in the amplitude. MLA (20 nM) itself reduced SCO frequency without affecting the amplitude but blocked nicotinic increase in [Ca2+]i oscillation frequency and amplitude. Furthermore, coadministration of both α4β2- and α7-nAChRs antagonists completely prevented nicotinic increment in [Ca2+]i oscillation frequency and amplitude. Thus, our results indicate that both α4β2- and α7-nAChRs mediated nicotine-induced [Ca2+]i oscillations, and two nAChR subtypes differentially regulated SCO.

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N-methyl-d-aspartate-evoked adenosine and inosine release from neurons requires extracellular calciumThis article is one of a selection of papers published in a special issue celebrating the 125th anniversary of the Faculty of Medicine at the University of Manitoba.

Canadian Journal of Physiology and Pharmacology ◽

10.1139/y09-075 ◽

2009 ◽

Vol 87 (10) ◽

pp. 850-858 ◽

Cited By ~ 7

Author(s):

Christina R. Zamzow ◽

Ratna Bose ◽

Fiona E. Parkinson

Keyword(s):

Nmda Receptors ◽

Cortical Neurons ◽

Nucleoside Transporter ◽

Stroke Models ◽

Intracellular Ca ◽

125Th Anniversary ◽

Rat Cortical Neurons ◽

Dependent Protein ◽

Potent Antagonist ◽

The University

The nucleoside adenosine (ADO) is a neuromodulator in brain. ADO and its metabolite inosine (INO) have been shown to increase cell viability in stroke models. During ischemia, extracellular levels of both ADO and INO are increased. In this study, we treated rat cortical neurons with N-methyl-d-aspartate (NMDA) to initiate excitotoxicity and then investigated the mechanisms of ADO and INO release. NMDA induced a significant increase in ADO and INO production. The effect of NMDA receptor antagonists on NMDA-evoked ADO and INO release was examined. MK-801 (1 µmol/L), a potent antagonist that lacks receptor subunit selectivity, completely blocked evoked release of both ADO and INO. Memantine (10 µmol/L), a lower affinity antagonist that also lacks subunit selectivity, blocked INO, but not ADO, release. Ifenprodil (10 µmol/L), an inhibitor selective for NMDA receptors containing the NR2B subunit, completely blocked evoked ADO and INO release. NVP-AAM077 (NVP, 0.4 µmol/L), an inhibitor selective for NMDA receptors containing the NR2A subunit, did not significantly block evoked release of either ADO or INO. Removal of extracellular Ca2+ abolished NMDA-evoked release of both ADO and INO. BAPTA (25 µmol/L), which chelates intracellular Ca2+, had no significant effect on either ADO or INO release unless extracellular Ca2+ was also removed. Inhibitors of Ca2+/calmodulin-dependent protein kinase II (CaMKII) prevented NMDA-evoked ADO and INO release and decreased nucleoside transporter function. These data indicate that NMDA-evoked ADO and INO release is dependent on subunit composition of NMDA receptors. As well, NMDA-evoked ADO and INO release requires nucleoside transporters and extracellular Ca2+ and is enhanced by activation of CaMKII.

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Mitochondrial transport in processes of cortical neurons is independent of intracellular calcium

AJP Cell Physiology ◽

10.1152/ajpcell.00230.2006 ◽

2006 ◽

Vol 291 (6) ◽

pp. C1193-C1197 ◽

Cited By ~ 16

Author(s):

Luis Beltran-Parrazal ◽

Héctor E. López-Valdés ◽

K. C. Brennan ◽

Mauricio Díaz-Muñoz ◽

Jean de Vellis ◽

...

Keyword(s):

Cortical Neurons ◽

Action Potentials ◽

Synaptic Activity ◽

Action Potential Firing ◽

Mitochondrial Movement ◽

Neuronal Processes ◽

Potential Firing ◽

Intracellular Ca ◽

Rat Cortical Neurons ◽

And Function

Mitochondria show extensive movement along neuronal processes, but the mechanisms and function of this movement are not clearly understood. We have used high-resolution confocal microscopy to simultaneously monitor movement of mitochondria and changes in intracellular [Ca2+] ([Ca2+]i) in rat cortical neurons. A significant percentage (27%) of the total mitochondria in cortical neuronal processes showed movement over distances of >2 μM. The average velocity was 0.52 μm/s. The velocity, direction, and pattern of mitochondrial movement were not affected by transient increases in [Ca2+]i associated with spontaneous firing of action potentials. Stimulation of Ca2+ transients with forskolin (10 μM) or bicuculline (10 μM), or sustained elevations of [Ca2+]i evoked by glutamate (10 μM) also had no effect on mitochondrial transit. Neither removal of extracellular Ca2+, depletion of intracellular Ca2+ stores with thapsigargin, or inhibition of synaptic activity with TTX (1 μM) or a cocktail of CNQX (10 μM) and MK801 (10 μM) affected mitochondrial movement. These results indicate that movement of mitochondria along processes is a fundamental activity in neurons that occurs independently of physiological changes in [Ca2+]i associated with action potential firing, synaptic activity, or release of Ca2+ from intracellular stores.

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Humanin Rescues Cultured Rat Cortical Neurons from NMDA-Induced Toxicity Not by NMDA Receptor

The Scientific World JOURNAL ◽

10.1155/2014/341529 ◽

2014 ◽

Vol 2014 ◽

pp. 1-8 ◽

Cited By ~ 5

Author(s):

Ai-Ling Cui ◽

Jian-Zhong Li ◽

Zhi-Bo Feng ◽

Guo-Lin Ma ◽

Liang Gong ◽

...

Keyword(s):

Lactate Dehydrogenase ◽

Nmda Receptor ◽

Cell Viability ◽

Cortical Neurons ◽

Morphological Changes ◽

Treated Group ◽

Dependent Manner ◽

Intracellular Ca ◽

Rat Cortical Neurons ◽

Ldh Release

Excitatory neurotoxicity has been implicated in many pathological situations and there is no effective treatment available. Humanin is a 24-aa peptide cloned from the brain of patients with Alzheimer’s disease (AD). In the present study, excitatory toxicity was induced by N-methyl-D-aspartate (NMDA) in primarily cultured rat cortical neurons. MTT assessment, lactate dehydrogenase (LDH) release, and calcein staining were employed to evaluate the protective activity of humanin on NMDA induced toxicity. The results suggested that NMDA (100 μmol/L, 2.5 hr) triggered neuronal morphological changes, lactate dehydrogenase (LDH) release (166% of the control), reduction of cell viability (about 50% of the control), and the decrease of living cell density (about 50% of the control). When pretreated with humanin, the toxicity was suppressed. The living cells’ density of humanin treated group was similar to that of control. The cell viability was attenuated dose-dependently (IC50= 0.132 nmol/L). The LDH release was also neutralized in a dose-dependent manner. In addition, the intracellular Ca2+overloading triggered by NMDA reverted quickly and humanin could not inhibit it. These findings indicate that humanin can rescue cortical neurons from NMDA-induced toxicity in rat but not through interfering with NMDA receptor directly.

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