Effect of repeated administration of morphine on the activity of extracellular signal regulated kinase in the mouse brain.
The present study was designed to determine whether chronic morphine treatment could influence the activity of extracellular signal regulated kinase (ERK) in the mouse brain. The single subcutaneous injection of morphine produced profound antinociception and an increase in phosphorylated-ERK (p-ERK) immunoreactivity in the pons/medulla, and these effects were blocked by a mu-opioid receptor antagonist, naloxone. The potency of antinociception induced by the second morphine injection at 24 h after the first morphine injection was similar to that by the first morphine injection. The p-ERK immunoreactivity in the pons/medulla obtained at 24 h after a single injection of morphine was not different from the control level. Repeated morphine injection once a day for 7 days resulted in a marked reduction of antinociception by morphine. The p-ERK immunoreactivity in the pons/medulla increased remarkably after 7 days repeated morphine injection. These data suggest that the sustained activation of ERK activity be associated with the development of antinociceptive tolerance to morphine in mice.
Narita
Minoru
M
Department of Toxicology, School of Pharmacy, Hoshi University, 2-4-41 Ebara, Shinagawa-Ku, Tokyo 142-8501, Japan.
Ioka
Masumi
M
Suzuki
Masami
M
Narita
Michiko
M
Suzuki
Tsutomu
T
D000701:Analgesics, Opioid / Q000494:pharmacology*; D000818:Animals; D004334:Drug Administration Schedule; D004361:Drug Tolerance / Q000502:physiology*; D008297:Male; D051379:Mice; D008813:Mice, Inbred ICR; D020928:Mitogen-Activated Protein Kinases / Q000187:drug effects* / Q000378:metabolism; D009020:Morphine / Q000494:pharmacology*; D009021:Morphine Dependence / Q000201:enzymology* / Q000503:physiopathology; D009270:Naloxone / Q000494:pharmacology; D009292:Narcotic Antagonists / Q000494:pharmacology; D009434:Neural Pathways / Q000187:drug effects / Q000201:enzymology; D009474:Neurons / Q000187:drug effects / Q000201:enzymology*; D009619:Nociceptors / Q000187:drug effects / Q000201:enzymology; D010146:Pain / Q000201:enzymology / Q000503:physiopathology; D010147:Pain Measurement / Q000187:drug effects; D017288:Pain Threshold / Q000187:drug effects / Q000502:physiology; D017450:Receptors, Opioid, mu / Q000187:drug effects / Q000378:metabolism; D012249:Rhombencephalon / Q000187:drug effects* / Q000201:enzymology; D015854:Up-Regulation / Q000187:drug effects* / Q000502:physiology
D000701:Analgesics, Opioid; D009292:Narcotic Antagonists; D017450:Receptors, Opioid, mu; D009270:Naloxone; D009020:Morphine; D020928:Mitogen-Activated Protein Kinases