Different mechanism of the antinociceptive effects of morphine and dermorphin tetrapeptide analogs

点击翻译按钮获取中文摘要

1) We investigated the role of mu1-opioid receptors on morphine-and dermorphin tetrapeptide analogs-induced antinociception using supraspinally mediated behavours exclusive of the spinal reflex as criteria in mice.2) Both intracerebroventricular (i.c.v.) and intrathecal (i.t.) administered morphine produced potent and significant antinociceptive activity in the tail-pressure test as a mechanical noxious stimulus. The pretreatment with naloxonazine failed to antagonize the activity.3) In the formalin test as a chemical noxious stimulus, licking and biting response was significantly inhibited by both i.c.v. and i.t. administered morphine. The activity was remarkably diminished by naloxonazine.4) In the hot plate test as a thermal noxious stimulus, both i.c.v. and i.t. administered-morphine induced antiniciceptive activity was significantly reduced by the pretreatment with naloxonazine.5) Pretreatment with naloxonazine antagonized the antinociceptive effects of both i.c.v. and i.t. dermorphin tetrapeptide analog (H-Tyr-DArg-Phe-beta-ala : TAPA) against response to mechanical and chemical stimuli.6) Although the pretreatment with naloxonazine was not antagonized the antinociceptive activity of i.c.v. TAPA-NH2 to both mechanical and chemical noxious stimuli and i.t. TAPA-NH2 to mechanical noxious stimulus, i.t. TAPA-NH2-induced antinociception to chemical stimulus was significantly reduced by naloxonazine.