capsazepine and acetovanillone

Despite considerable research, the mechanisms of neuropathic pain induced by excessive oxidative stress production and overload calcium ion (Ca

Topics: Acetophenones; Action Potentials; Animals; Calcium Signaling; Capsaicin; Cells, Cultured; Cinnamates; Ganglia, Spinal; Indoles; Male; Maleimides; NADPH Oxidases; Neurons; ortho-Aminobenzoates; Oxidative Stress; Protein Kinase C; Rats; Rats, Wistar; Tetradecanoylphorbol Acetate; TRPM Cation Channels; TRPV Cation Channels

Using electrophysiological and optical techniques, we studied the mechanisms by which cholesterol depletion stimulates spontaneous transmitter release by exocytosis at the frog neuromuscular junction. We found that methyl-β-cyclodextrin (MCD, 10 mM)-mediated exhaustion of cholesterol resulted in the enhancement of reactive oxygen species (ROS) production, which was prevented by the antioxidant N-acetyl cysteine (NAC) and the NADPH oxidase inhibitor apocynin. An increase in ROS levels occurred both extra- and intracellularly, and it was associated with lipid peroxidation in synaptic regions. Cholesterol depletion provoked a rise in the intracellular Ca(2+) concentration, which was diminished by NAC and transient receptor potential vanilloid (TRPV) channel blockers (ruthenium red and capsazepine). By contrast, the MCD-induced rise in [Ca(2+)]i remained unaffected if Ca(2+) release from endoplasmic stores was blocked by TMB8 (8-(diethylamino)octyl-3,4,5-trimethoxybenzoate hydrochloride). The effects of cholesterol depletion on spontaneous release and exocytosis were significantly reduced by the antioxidant, intracellular Ca(2+) chelation with BAPTA-AM and blockers of TRPV channels. Bath application of the calcineurin antagonist cyclosporine A blocked MCD-induced enhancement of spontaneous release/exocytosis, whereas okadaic acid, an inhibitor of phosphatases PP1 and PP2A, had no effect. Thus, our findings indicate that enhancement of spontaneous exocytosis induced by cholesterol depletion may depend on ROS generation, leading to an influx of Ca(2+) via TRPV channels and, subsequently, activation of calcineurin.

Topics: Acetophenones; Acetylcysteine; Animals; beta-Cyclodextrins; Calcium; Calcium Signaling; Capsaicin; Cholesterol; Cyclosporine; Exocytosis; Neuromuscular Junction; Okadaic Acid; Ranidae; Reactive Oxygen Species; Ruthenium Red; Synaptic Membranes; TRPV Cation Channels