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Hydrogen Peroxide (H 2 O 2 ) Augments Intracellular Ca ++ via Voltage‐Gated Ca ++ Channels in Isolated Nucleus Tractus Solitarii (nTS) Neurons
Author(s) -
Ostrowski Tim,
PoloParada Luis,
Kline David
Publication year - 2015
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.29.1_supplement.859.9
Subject(s) - extracellular , chemistry , thapsigargin , nifedipine , mibefradil , intracellular , cytosol , voltage dependent calcium channel , channel blocker , fura 2 , biophysics , calcium , endocrinology , medicine , biochemistry , biology , enzyme , organic chemistry
Central neuronal activity and its modulation via 2 nd messengers within the nTS is fundamental for cardiorespiratory control. We have previously shown that H 2 O 2 in the nTS augments action potential discharge. Here we examined the role of H 2 O 2 on Ca ++ homeostasis in primary nTS cultures using the ratiometric dye Fura 2‐AM. H 2 O 2 dose dependently (100‐500µM H 2 O 2 , 1 min) augmented intracellular Ca ++ . The majority of nTS cells (79% of 24 cells) responded to 200µM H 2 O 2 with an increase in cytosolic Ca ++ of 16.0 ±2.8% ( p 蠄0.01 vs. vehicle). To identify the source for the Ca ++ rise we tested 200µM H 2 O 2 in the presence of Thapsigargin (TG; 1µM) to deplete internal Ca ++ stores. In the presence of TG, there was a reduction in the number of H 2 O 2 responding cells (45% of 46 cells), yet those that did respond increased cytosolic Ca ++ by 72.5 ±21.7% ( p 蠄0.05 vs. vehicle & 200µM H 2 O 2 alone). Removing extracellular Ca ++ (0 Ca ++ with 1mM EDTA) strongly decreased the number of H 2 O 2 responders (10% of 23) as well as the augmentation of Ca ++ in the remaining responders. To examine the potential Ca ++ channel responsible we included specific Ca ++ channel blockers during H 2 O 2 . The number of responders to H 2 O 2 was reduced to 40%, 40%, 34% and 20% by blocking L‐type (5µM Nifedipine), N‐Type (0.1µM ω‐conotoxin GVIA), T‐type (5µM Mibefradil) and P/Q/N‐type (ω‐conotoxin MVIIIC) Ca ++ channels, respectively (N=20‐28). Altogether, elevations in cytosolic Ca ++ in nTS cells by H 2 O 2 likely occurs through several available Ca ++ channels that contribute to the cellular hyperexcitability. Supported by: RO1 HL098602, AHA 12POST11670002