Role of vagal afferents in the antinociception produced by morphine and U-50,488H in the colonic pain reflex in rats.
The mechanisms underlying the antinociception induced by morphine or U-50,488H (trans-(+-)-3,4-dichloro-N-methyl-N-(2-[1-pyrrolidinyl]- cyclohexyl)benzeneacetamide) against painful colonic distension were examined in anaesthetized rats. The respective ED50 values for morphine and U-50,488H were 0.34 and 0.35 mg/kg for the i.v. route, and 1.68 and 167 micrograms/rat for the i.c.v. route. Morphine was active by the intrathecal route (ED50 = 7.8 micrograms) whereas U-50,488H had no effect at doses up to 100 micrograms/rat. The morphine response was selectively antagonized by naloxone (30 micrograms/kg i.v.) whereas that of U-50,488H was blocked by nor-binaltorphimine (10 mg/kg s.c.). Bilateral vagotomy abolished the response to morphine at 0.35 mg/kg i.v. and reduced by 41.3% that to 1 mg/kg morphine, but had no effect on that to U-50,488H or i.c.v. morphine (10 micrograms/rat). It is concluded that peripheral mu- and kappa-opioid receptors may produce antinociception for colonic pain and that vagal integrity is required for mu-opioid but not kappa-opioid peripheral antinociception.
Diop
L
L
Institut de Recherche Jouveinal, Fresnes, France.
Rivière
P J
PJ
Pascaud
X
X
Dassaud
M
M
Junien
J L
JL
D019900:3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; D000700:Analgesics / Q000494:pharmacology*; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D003106:Colon / Q000187:drug effects*; D007276:Injections, Intraventricular; D007278:Injections, Spinal; D008297:Male; D009020:Morphine / Q000008:administration & dosage / Q000494:pharmacology*; D009270:Naloxone / Q000494:pharmacology; D009271:Naltrexone / Q000031:analogs & derivatives / Q000494:pharmacology; D009475:Neurons, Afferent / Q000187:drug effects; D010146:Pain / Q000188:drug therapy*; D011759:Pyrrolidines / Q000008:administration & dosage / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D017473:Receptors, Opioid, kappa / Q000187:drug effects / Q000378:metabolism; D017450:Receptors, Opioid, mu / Q000187:drug effects / Q000378:metabolism; D012018:Reflex; D014628:Vagotomy; D014630:Vagus Nerve / Q000187:drug effects* / Q000502:physiology
D000700:Analgesics; D011759:Pyrrolidines; D017473:Receptors, Opioid, kappa; D017450:Receptors, Opioid, mu; D009270:Naloxone; C051844:norbinaltorphimine; D009271:Naltrexone; D019900:3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; D009020:Morphine