Tamaddonfard Esmaeal, Erfanparast Amir, Khalilzadeh Emad
Department of Basic Sciences, Faculty of Veterinary Medicine, Urmia University, Urmia, Iran.
Vet Res Forum. 2012 Spring;3(2):91-5.
In this study, the effects of subcutaneous (SC) injection of pilocarpine (a cholinomimetic agent) and atropine (a muscarinic receptors antagonist) were investigated on a tonic model of orofacial pain in rats. The contribution of the endogenous analgesic opioid system was assessed using naloxone (an opioid receptors antagonist). Tonic orofacial pain was induced by SC injection of a diluted formalin solution (1%, 50 μL) in the right upper lip, and the time spent face rubbing was measured in five min blocks for 1 h. Formalin induced a biphasic (first phase: 0-5 min and second phase: 15-35 min) pain response. Pilocarpine significantly (P < 0.05) suppressed both phases of orofacial pain. Atropine did not have any effect and naloxone non-significantly increased the intensity of pain when used alone. In the pre-injection examinations, atropine prevented, but naloxone did not reverse the antinociceptive effect of pilocarpine. The results indicated that SC injection of formalin in the orofacial region induced a marked biphasic pain. Pilocarpine via muscarinic cholinergic receptors produced antinociceptive effect in the orofacial formalin-induced pain. The endogenous opioid analgesic system may not have a role in pilocarpine-induced antinociception.
在本研究中，研究了皮下注射毛果芸香碱（一种拟胆碱剂）和阿托品（一种毒蕈碱受体拮抗剂）对大鼠口面部疼痛紧张性模型的影响。使用纳洛酮（一种阿片受体拮抗剂）评估内源性镇痛阿片系统的作用。通过在右上唇皮下注射稀释的福尔马林溶液（1%，50μL）诱导口面部紧张性疼痛，并在1小时内以5分钟为间隔测量擦脸时间。福尔马林诱导双相性（第一阶段：0 - 5分钟，第二阶段：15 - 35分钟）疼痛反应。毛果芸香碱显著（P < 0.05）抑制了口面部疼痛的两个阶段。阿托品没有任何作用，单独使用时纳洛酮非显著增加疼痛强度。在注射前检查中，阿托品阻止了毛果芸香碱的镇痛作用，但纳洛酮并未逆转其作用。结果表明，在口面部区域皮下注射福尔马林可诱导明显的双相性疼痛。毛果芸香碱通过毒蕈碱胆碱能受体在口面部福尔马林诱导的疼痛中产生镇痛作用。内源性阿片镇痛系统可能在毛果芸香碱诱导的镇痛中不起作用。
