PT  - JOURNAL ARTICLE
AU  - Marat V. Avshalumov
AU  - Billy T. Chen
AU  - Tibor Koós
AU  - James M. Tepper
AU  - Margaret E. Rice
TI  - Endogenous Hydrogen Peroxide Regulates the Excitability of Midbrain Dopamine Neurons via ATP-Sensitive Potassium Channels
AID  - 10.1523/JNEUROSCI.4701-04.2005
DP  - 2005 Apr 27
TA  - The Journal of Neuroscience
PG  - 4222--4231
VI  - 25
IP  - 17
4099  - http://www.jneurosci.org/content/25/17/4222.short
4100  - http://www.jneurosci.org/content/25/17/4222.full
SO  - J. Neurosci.2005 Apr 27; 25
AB  - ATP-sensitive K+ (KATP) channels link metabolic state to cell excitability. Here, we examined regulation of KATP channels in substantia nigra dopamine neurons by hydrogen peroxide (H2O2), which is produced in all cells during aerobic metabolism. Blockade of KATP channels by glibenclamide (100 nm) or depletion of intracellular H2O2 by including catalase, a peroxidase enzyme, in the patch pipette increased the spontaneous firing rate of all dopamine neurons tested in guinea pig midbrain slices. Using fluorescence imaging with dichlorofluorescein to visualize intracellular H2O2, we found that moderate increases in H2O2 during partial inhibition of glutathione (GSH) peroxidase by mercaptosuccinate (0.1-0.3 mm) had no effect on dopamine neuron firing rate. However, with greater GSH inhibition (1 mm mercaptosuccinate) or application of exogenous H2O2, 50% of recorded cells showed KATP channel-dependent hyperpolarization. Responsive cells also hyperpolarized with diazoxide, a selective opener for KATP channels containing sulfonylurea receptor SUR1 subunits, but not with cromakalim, a selective opener for SUR2-based channels, indicating that SUR1-based KATP channels conveyed enhanced sensitivity to elevated H2O2. In contrast, when endogenous H2O2 levels were increased after inhibition of catalase, the predominant peroxidase in the substantia nigra, with 3-amino-1,2,4-triazole (1 mm), all dopamine neurons responded with glibenclamide-reversible hyperpolarization. Fluorescence imaging of H2O2 indicated that catalase inhibition rapidly amplified intracellular H2O2, whereas inhibition of GSH peroxidase, a predominantly glial enzyme, caused a slower, smaller increase, especially in nonresponsive cells. Thus, endogenous H2O2 modulates neuronal activity via KATP channel opening, thereby enhancing the reciprocal relationship between metabolism and excitability.