Premium
Enhanced expression and activity of NAD(P)H oxidase in mouse periaqueductal gray neurons during morphine antinociceptive tolerance
Author(s) -
Chen Li,
Hull Lynn C.,
Lee Thomas T.,
Zhang Guo,
Smith Forrest L.,
Dewey William L.,
Li PinLan
Publication year - 2006
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.20.4.a242
Subject(s) - nad+ kinase , chemistry , morphine , periaqueductal gray , nad(p)h oxidase , nociception , oxidase test , pharmacology , biochemistry , enzyme , endocrinology , central nervous system , biology , receptor , midbrain
This study tested the hypothesis that NAD(P)H oxidase plays a role in morphine antinociceptive tolerance formation. Antinociceptive tolerance was induced in male Swiss Webster mice following morphine treatment for 24 hours. The effects of chronic morphine treatment on NAD(P)H oxidase mRNA levels, protein levels, and enzyme activity were determined in the periaqueductal gray (PAG) and cerebral cortex from these mice. NAD(P)H oxidase activity, as measured by the conversion rate of NADH to NAD + using HPLC, significantly increased by 47.6% in homogenates from the PAG, while NAD(P)H oxidase activity was not significantly altered in the cerebral cortex. The NAD(P)H oxidase inhibitor, diphenylene iodonium, completely blocked basal and morphine‐increased NAD(P)H oxidase activity in the PAG. Western blot analysis revealed that protein levels of the NADPH oxidase subunits gp91 phox , p47 phox , and p67 phox significantly increased in the PAG of morphine‐tolerant mice, but not in the cerebral cortex. Real‐time PCR (RT‐PCR) analysis revealed that gp91 phox mRNA levels were significantly increased in the PAG of morphine‐tolerant mice. These results indicate that NAD(P)H oxidase is present in PAG neurons and that chronic morphine treatment increases the expression of various subunits of this enzyme, leading to enhanced superoxide production in this brain area. Future studies will continue to elucidate the functional significance of enhanced NAD(P)H oxidase activity in morphine antinociceptive tolerance expression. (Supported by NIH Grants HL57244, HL75316 and DA01647).