Differential involvement of opioid receptors in stress-induced antinociception caused by repeated exposure to forced walking stress in mice.
We examined the effects of repeated exposure to forced walking stress for 6 h once a day for 0, 6 and 9 consecutive days on formalin-induced paw licking in mice. In each observation period, stress-induced antinociception (SIA) was observed only in the late phase (from 10 to 30 min), but not in the early phase (from 0 to 10 min) of formalin-induced paw licking in mice. Moreover, it was hard to develop tolerance even by daily exposure to stress for 6 days, although SIA for 9 days decreased compared with those for 0 and 6 days. Naloxone (10 mg/kg), an opioid-receptor antagonist, was effective in reducing the SIA induced by forced walking stress for 6 days and/or 9 days, but not for 0 days. Furthermore, the experiments with selective opioid-receptor antagonists, beta-funaltrexamine (mu) naltrindol (delta), or nor-binaltorphimine (kappa) demonstrated that SIA induced by forced walking stress for 9 successive days may be mediated through opioid delta- and kappa-receptors. Finally, although SIA seemed to be a unitary phenomenon, the present results strengthened the idea that SIA is induced by exposure to forced walking stress with characteristics dependent on the duration of exposure.
Onodera
K
K
Department of Pharmacology, School of Dentistry, Tohoku University, Sendai, Japan. kenjio@mail.cc.tohoku.ac.jp
Sakurada
S
S
Furuta
S
S
Yonezawa
A
A
Arai
K
K
Hayashi
T
T
Katsuyama
S
S
Sato
T
T
Miyazaki
S
S
Kisara
K
K
D000818:Animals; D005557:Formaldehyde; D008297:Male; D051379:Mice; D009270:Naloxone / Q000494:pharmacology; D009271:Naltrexone / Q000031:analogs & derivatives* / Q000494:pharmacology; D009292:Narcotic Antagonists / Q000494:pharmacology; D010146:Pain / Q000139:chemically induced / Q000378:metabolism* / Q000503:physiopathology; D010147:Pain Measurement / Q000187:drug effects; D011957:Receptors, Opioid / Q000187:drug effects / Q000378:metabolism*; D013312:Stress, Physiological / Q000503:physiopathology*; D016138:Walking
D009292:Narcotic Antagonists; D011957:Receptors, Opioid; D005557:Formaldehyde; D009270:Naloxone; C051844:norbinaltorphimine; D009271:Naltrexone; C024524:beta-funaltrexamine; C055382:naltrindole