Potentiation of mGlu7 receptor-mediated glutamate release at nerve terminals containing N and P/Q type Ca2+ channels

Background: Regulation of glutamate release is crucial for maintaining normal brain function, but excess glutamate release is implicated in many neuropathological conditions. Therefore, the minimum glutamate release from presynaptic nerve terminals is an important neuroprotective mechanism. Objective: In this mini-review, we analyze the three B vitamins, namely vitamin B2 (riboflavin), vitamin B6 (pyridoxine), and vitamin B12 (cyanocobalamin), that affect the 4-aminopyridine (4-AP)-evoked glutamate release from presynaptic nerve terminal in rat and discuss their neuroprotective role. Methods: In this study, the measurements include glutamate release, DiSC3(5), and Fura-2. Results: The riboflavin, pyridoxine, and cyanocobalamin produced significant inhibitory effects on 4-aminopyridine-evoked glutamate release from rat cerebrocortical nerve terminals (synaptosomes) in a dose-dependent relationship. These presynaptic inhibitory actions of glutamate release are attributed to inhibition of physiologic Ca2+-dependent vesicular exocytosis but not Ca2+-independent nonvesicular release. These effects also did not affect membrane excitability, while diminished cytosolic [Ca2+]c through a reduction of direct Ca2+ influx via Cav2.2 (N-type) and Cav2.1 (P/Q-type) Ca2+ channels, rather than through indirect Ca2+ induced Ca2+ release from ryanodine-sensitive intracellular stores. Furthermore, their effects were attenuated by GF109203X and Ro318220, two protein kinase C (PKC) inhibitors, suggesting suppression of PKC activity. Taken together, these results suggest that riboflavin, pyridoxine, and cyanocobalamin inhibit presynaptic vesicular glutamate release from rat cerebrocortical synaptosomes, through the depression Ca2+ influx via voltage-dependent Cav2.2 (N-type) and Cav2.1 (P/Q-type) Ca2+ channels, and PKC signaling cascade. Conclusion: Therefore, these B vitamins may reduce the strength of glutamatergic synaptic transmission and is of considerable importance as potential targets for therapeutic agents in glutamate-induced excitation-related diseases.

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Widespread Inhibition of Sodium Channel–dependent Glutamate Release from Isolated Nerve Terminals by Isoflurane and Propofol

Anesthesiology ◽

10.1097/00000542-200112000-00027 ◽

2001 ◽

Vol 95 (6) ◽

pp. 1460-1466 ◽

Cited By ~ 70

Author(s):

Ratnakumari Lingamaneni ◽

Martin L. Birch ◽

Hugh C. Hemmings

Keyword(s):

Cerebral Cortex ◽

Guinea Pig ◽

Rat Brain ◽

Glutamate Release ◽

Brain Regions ◽

Rat Striatum ◽

Nerve Terminals ◽

Na Channels ◽

Rat Brain Regions ◽

Ca2 Channels

Background Controversy persists concerning the mechanisms and role of general anesthetic inhibition of glutamate release from nerve endings. To determine the generality of this effect and to control for methodologic differences between previous studies, the authors analyzed the presynaptic effects of isoflurane and propofol on glutamate release from nerve terminals isolated from several species and brain regions. Methods Synaptosomes were prepared from rat, mouse, or guinea pig cerebral cortex and also from rat striatum and hippocampus. Release of endogenous glutamate evoked by depolarization with 20 microm veratridine (which opens voltage-dependent Na+ channels by preventing inactivation) or by 30 mm KCl (which activates voltage-gated Ca2+ channels by membrane depolarization) was monitored using an on-line enzyme-linked fluorometric assay. Results Glutamate release evoked by depolarization with increased extracellular KCl was not significantly inhibited by isoflurane up to 0.7 mM ( approximately 2 minimum alveolar concentration; drug concentration for half-maximal inhibition [IC50] > 1.5 mM) [corrected] or propofol up to 40 microm in synaptosomes prepared from rat, mouse, or guinea pig cerebral cortex, rat hippocampus, or rat striatum. Lower concentrations of isoflurane or propofol significantly inhibited veratridine-evoked glutamate release in all three species (isoflurane IC50 = 0.41-0.50 mm; propofol IC50 = 11-18 microm) and rat brain regions. Glutamate release was evoked by veratridine or increased KCl (from 5 to 35 mM) to assess the involvement of presynaptic ion channels as targets for drug actions [corrected]. Conclusions Isoflurane and propofol inhibited Na+ channel-mediated glutamate release evoked by veratridine with greater potency than release evoked by increased KCl in synaptosomes prepared from three mammalian species and three rat brain regions. These findings are consistent with a greater sensitivity to anesthetics of presynaptic Na+ channels than of Ca2+ channels coupled to glutamate release. This widespread presynaptic action of general anesthetics is not mediated by potentiation of gamma-aminobutyric acid type A receptors, though additional mechanisms may be involved.

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mGluR7 inhibits glutamate release through a PKC-independent decrease in the activity of P/Q-type Ca2+ channels and by diminishing cAMP in hippocampal nerve terminals

European Journal of Neuroscience ◽

10.1111/j.1460-9568.2007.05660.x ◽

2007 ◽

Vol 26 (2) ◽

pp. 312-322 ◽

Cited By ~ 26

Author(s):

Ricardo Martín ◽

Magdalena Torres ◽

José Sánchez-Prieto

Keyword(s):

Glutamate Release ◽

Nerve Terminals ◽

Ca2 Channels

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Natural Product Isoliquiritigenin Activates GABAB Receptors to Decrease Voltage-Gate Ca2+ Channels and Glutamate Release in Rat Cerebrocortical Nerve Terminals

Biomolecules ◽

10.3390/biom11101537 ◽

2021 ◽

Vol 11 (10) ◽

pp. 1537

Author(s):

Tzu-Yu Lin ◽

Cheng-Wei Lu ◽

Pei-Wen Hsieh ◽

Kuan-Ming Chiu ◽

Ming-Yi Lee ◽

...

Keyword(s):

Gabab Receptor ◽

Glutamate Release ◽

Receptor Activation ◽

Gabab Receptors ◽

Nerve Terminals ◽

Type B ◽

Kinase C ◽

Acid Type ◽

Dependent Inhibition ◽

Ca2 Channels

Reduction in glutamate release is a key mechanism for neuroprotection and we investigated the effect of isoliquiritigenin (ISL), an active ingredient of Glycyrrhiza with neuroprotective activities, on glutamate release in rat cerebrocortical nerve terminals (synaptosomes). ISL produced a concentration-dependent inhibition of glutamate release and reduced the intraterminal [Ca2+] increase. The inhibition of glutamate release by ISL was prevented after removing extracellular Ca2+ or blocking P/Q-type Ca2+ channels. This inhibition was mediated through the γ-aminobutyric acid type B (GABAB) receptors because ISL was unable to inhibit glutamate release in the presence of baclofen (an GABAB agonist) or CGP3548 (an GABAB antagonist) and docking data revealed that ISL interacted with GABAB receptors. Furthermore, the ISL inhibition of glutamate release was abolished through the inhibition of Gi/o-mediated responses or Gβγ subunits, but not by 8-bromoadenosine 3′, 5′-cyclic monophosphate or adenylate cyclase inhibition. The ISL inhibition of glutamate release was also abolished through the inhibition of protein kinase C (PKC), and ISL decreased the phosphorylation of PKC. Thus, we inferred that ISL, through GABAB receptor activation and Gβγ-coupled inhibition of P/Q-type Ca2+ channels, suppressed the PKC phosphorylation to cause a decrease in evoked glutamate release at rat cerebrocortical nerve terminals.

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Chlorogenic Acid Decreases Glutamate Release from Rat Cortical Nerve Terminals by P/Q-Type Ca2+ Channel Suppression: A Possible Neuroprotective Mechanism

International Journal of Molecular Sciences ◽

10.3390/ijms222111447 ◽

2021 ◽

Vol 22 (21) ◽

pp. 11447

Author(s):

Yi-Chieh Hung ◽

Yi-Hsiu Kuo ◽

Pei-Wen Hsieh ◽

Ting-Yang Hsieh ◽

Jinn-Rung Kuo ◽

...

Keyword(s):

Chlorogenic Acid ◽

Cortical Neurons ◽

Neuronal Damage ◽

Glutamate Release ◽

Synapsin I ◽

Nerve Terminals ◽

Neurotransmitter System ◽

Excitotoxic Damage ◽

Acid Administration ◽

Ca2 Channels

The glutamatergic neurotransmitter system has received substantial attention in research on the pathophysiology and treatment of neurological disorders. The study investigated the effect of the polyphenolic compound chlorogenic acid (CGA) on glutamate release in rat cerebrocortical nerve terminals (synaptosomes). CGA inhibited 4-aminopyridine (4-AP)-induced glutamate release from synaptosomes. This inhibition was prevented in the absence of extracellular Ca2+ and was associated with the inhibition of 4-AP-induced elevation of Ca2+ but was not attributed to changes in synaptosomal membrane potential. In line with evidence observed through molecular docking, CGA did not inhibit glutamate release in the presence of P/Q-type Ca2+ channel inhibitors; therefore, CGA-induced inhibition of glutamate release may be mediated by P/Q-type Ca2+ channels. CGA-induced inhibition of glutamate release was also diminished by the calmodulin and Ca2+/calmodilin-dependent kinase II (CaMKII) inhibitors, and CGA reduced the phosphorylation of CaMKII and its substrate, synapsin I. Furthermore, pretreatment with intraperitoneal CGA injection attenuated the glutamate increment and neuronal damage in the rat cortex that were induced by kainic acid administration. These results indicate that CGA inhibits glutamate release from cortical synaptosomes by suppressing P/Q-type Ca2+ channels and CaMKII/synapsin I pathways, thereby preventing excitotoxic damage to cortical neurons.

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