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

1)我们研究了mu1-阿片受体在吗啡和真皮吗啡四肽类似物诱导的抗痛觉中的作用，以脊柱反射以外的棘上介导行为为标准。2)脑室内注射和鞘内注射吗啡作为一种机械有害刺激，在尾压试验中均产生了强效且显著的抗伤害性活性。纳洛唑嗪预处理不能拮抗活性。3)在福尔马林实验中，注射吗啡和静脉注射吗啡均能显著抑制小鼠的舔咬反应。纳洛唑嗪明显降低了活性。4)在热板实验中，作为热有害刺激的吗啡在体外注射和体外注射时，经纳洛唑嗪预处理后均显著降低了小鼠的抗炎活性。5)纳洛唑嗪预处理可拮抗i.c.v.和i.t.真皮吗啡四肽类似物（h - tyr - darg - ph - β -ala: TAPA）对机械和化学刺激反应的抗伤害性作用。6)虽然纳洛唑嗪预处理不能拮抗tpa - nh2对机械、化学有害刺激和机械有害刺激的抗痛觉活性，但纳洛唑嗪显著降低了tpa - nh2对化学刺激的抗痛觉活性。

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.