title: Nitric oxide/cyclic guanosine monophosphate system in the spinal cord differentially modulates intracerebroventricularly administered morphine- and beta-endorphin-induced antinociception in the mouse.
abstract: Our study was designed to study the modulatory role of nitric oxide/cyclic guanosine monophosphate in the spinal cord on the antinociception induced by morphine and beta-endorphin given supraspinally. The antinociception was assessed by the tail-flick test in male ICR mice. The antinociception induced by intracerebroventricularly (i.c.v.) administered morphine was potentiated by intrathecal (i.t) injection of N omega-nitro-L-arginine (2 micrograms), hemoglobin (120 micrograms) or methylene blue (5 micrograms), but was attenuated by i.t. administered L-arginine (20 micrograms) or 3-morpholino-sydnonimine (SIN-1, 5 micrograms). In contrast, the antinociception induced by i.c.v. administered beta-endorphin was attenuated by i.t. pretreatment with N omega-nitro-L-arginine (2 micrograms) and the attenuation of beta-endorphin-induced antinociception by N omega-nitro-L-arginine was reversed by i.t. administered L-arginine (20 micrograms). The antinociception induced by i.c.v. administered beta-endorphin was also attenuated by i.t. administration of hemoglobin (120 micrograms) or methylene blue (5 micrograms). Intrathecal pretreatment with L-arginine did not affect i.c.v. administered beta-endorphin-induced antinociception. It is concluded that the inhibition of nitric oxide/cyclic guanosine monophosphate system in the spinal cord potentiates i.c.v. administered morphine-induced antinociception but attenuates i.c.v. beta-endorphin-induced antinociception. The activation of nitric oxide/cyclic guanosine monophosphate system in the spinal cord attenuates i.c.v. administered morphine-induced antinociception but does not affect i.c.v. administered beta-endorphin-induced antinociception.
authors.affiliation: Department of Anesthesiology, Medical College of Wisconsin, Milwaukee, USA.
authors.forename: J Y
authors.initials: JY
authors.lastname: Xu
authors.forename: L F
authors.initials: LF
authors.lastname: Tseng
mesh_terms: D000700:Analgesics / Q000494:pharmacology; D000818:Animals; D001120:Arginine / Q000031:analogs & derivatives / Q000494:pharmacology; D006152:Cyclic GMP / Q000502:physiology*; D004305:Dose-Response Relationship, Drug; D006454:Hemoglobins / Q000494:pharmacology; D007276:Injections, Intraventricular; D007278:Injections, Spinal; D008297:Male; D008751:Methylene Blue / Q000494:pharmacology; D051379:Mice; D008813:Mice, Inbred ICR; D009020:Morphine / Q000008:administration & dosage / Q000494:pharmacology*; D009569:Nitric Oxide / Q000502:physiology*; D009842:Oligopeptides / Q000008:administration & dosage / Q000494:pharmacology; D013116:Spinal Cord / Q000502:physiology*; D001615:beta-Endorphin / Q000008:administration & dosage / Q000494:pharmacology*
chemical_list: D000700:Analgesics; D006454:Hemoglobins; D009842:Oligopeptides; C060209:deltorphin II, Ala(2)-; D009569:Nitric Oxide; D001615:beta-Endorphin; D009020:Morphine; D001120:Arginine; D006152:Cyclic GMP; D008751:Methylene Blue