Involvement of brain protein kinase C in nitrous oxide-induced antinociception in mice.
Exposure of mice to the anesthetic gas nitrous oxide (N(2)O) produces a marked antinociceptive effect. Protein kinase C is a key regulatory enzyme that may be targeted by general anesthetics. However, a relationship between N(2)O-induced antinociception and protein kinase C has yet to be established. The present study was conducted to identify whether protein kinase C might influence N(2)O-induced antinociception in mice. Regular exposure (11 min) to N(2)O produced concentration-dependent antinociception in mice, as determined using the abdominal constriction test. N(2)O-induced antinociception was attenuated by i.c.v. pretreatment with phorbol 12,13-dibutyrate, a protein kinase C activator. This phorbol 12,13-dibutyrate antagonism of N(2)O-induced antinociception was reversed by i.c.v. pretreatment with calphostin C, a protein kinase C inhibitor. Long-term exposure (41 min in total, including 30 min prior to, and 11 min of analgesic testing) to 70% N(2)O produced reduced analgesic effects, compared with regular exposure to 70% N(2)O, thus indicating acute tolerance to N(2)O-induced antinociception. However, mice pretreated with calphostin C, chelerythrine, which is another protein kinase C inhibitor, and phorbol 12,13-dibutyrate, did not develop acute tolerance. Regarding activation of protein kinase C, regular exposure to 70% N(2)O did not increase protein kinase C within the membrane fraction of brain tissue, as determined by immunoblot analysis, but long-term exposure to 70% N(2)O did. The i.c.v. pretreatment with calphostin C and phorbol 12,13-dibutyrate prevented the increase in protein kinase C observed with long-term exposure to 70% N(2)O. These results suggest that brain protein kinase C negatively regulates the antinociceptive effect of N(2)O, and that activation of brain protein kinase C is related to the development of acute tolerance to N(2)O-induced antinociception in mice.
Department of Pharmacotherapeutics, Showa Pharmaceutical University, P.O. Box 3-3165, Higashitamagawagakuen, Tokyo 194-8543, Japan.
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M
Ishikawa
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Y
Matsushita
K
K
Abe
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I
Utsunomiya
K
K
Hoshi
R M
RM
Quock
K
K
Taguchi
D000700:Analgesics / Q000494:pharmacology*; D000704:Analysis of Variance; D000818:Animals; D015153:Blotting, Western / Q000379:methods; D001921:Brain / Q000201:enzymology*; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects / Q000502:physiology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D009281:Naphthalenes / Q000494:pharmacology; D009609:Nitrous Oxide / Q000494:pharmacology*; D009619:Nociceptors / Q000187:drug effects*; D010147:Pain Measurement; D015240:Phorbol 12,13-Dibutyrate / Q000494:pharmacology; D011493:Protein Kinase C / Q000378:metabolism*
D000700:Analgesics; D004791:Enzyme Inhibitors; D009281:Naphthalenes; D015240:Phorbol 12,13-Dibutyrate; D011493:Protein Kinase C; C058819:calphostin C; D009609:Nitrous Oxide