Reisi Zahra, Haghparast Amir, Pahlevani Pouyan, Shamsizadeh Ali, Haghparast Abbas
Physiology-Pharmacology Research Center, Rafsanjan University of Medical Sciences, Rafsanjan, Iran.
Neuroscience Research Center, Shahid Beheshti University of Medical Sciences, PO Box 19615-1178, Tehran, Iran; Faculty of Dentistry, International Branch of Shahid Beheshti University of Medical Sciences, Tehran, Iran.
Pharmacol Biochem Behav. 2014 Sep;124:220-5. doi: 10.1016/j.pbb.2014.06.015. Epub 2014 Jun 21.
The hippocampus is a region of the brain that serves several functions. The dopaminergic system acts through D1- and D2-like receptors to interfere in pain modulation and the opioid receptors play major roles in analgesic processes and there are obvious overlaps between these two systems. The present study investigated the interaction between the opioidergic and dopaminergic systems in the dorsal hippocampus (CA1) region for formalin-induced orofacial pain. Two guide cannulae were stereotaxically implanted in the CA1 region and morphine (0.5, 1, 2 and 4 μg/0.5 μl saline) and naloxone (0.3, 1 and 3 μg/0.5 μl saline) were used as the opioid receptor agonist and antagonist, respectively. SKF-38393 (1 μg/0.5 μl saline) was used as a D1-like receptor agonist, quinpirole (2 μg/0.5 μl saline) as a D2-like receptor agonist, SCH-23390 (0.5 μg/0.5 μl saline) as a D1-like receptor antagonist and sulpiride (3 μg/0.5 μl DMSO) as a D2-like receptor antagonist. To induce orofacial pain, 50 μl of 1% formalin was subcutaneously injected into the left side of the upper lip. Our results showed that different doses of morphine significantly reduced orofacial pain in both phases induced by formalin. Naloxone (1 and 3 μg) reversed morphine induced analgesia in CA1. SKF-38393 and quinpirole with naloxone (1 μg) significantly decreased formalin-induced orofacial pain in both phases. SCH-23390 had no effect on the antinociceptive response of morphine in both phases of orofacial pain. Sulpiride reversed the antinociceptive effects of morphine only in the first phase, but this result was not significant. Our findings suggest that there is cross-talk between the opioidergic and dopaminergic systems. Opioidergic neurons also exerted antinociceptive effects by modulation of the dopaminergic system in the CA1 region of the brain.
海马体是大脑中具有多种功能的一个区域。多巴胺能系统通过D1样和D2样受体发挥作用，干扰疼痛调节，而阿片受体在镇痛过程中起主要作用，这两个系统之间存在明显重叠。本研究调查了背侧海马体（CA1）区域中阿片能系统与多巴胺能系统在福尔马林诱导的口面部疼痛中的相互作用。通过立体定位将两根引导套管植入CA1区域，并分别使用吗啡（0.5、1、2和4μg/0.5μl生理盐水）和纳洛酮（0.3、1和3μg/0.5μl生理盐水）作为阿片受体激动剂和拮抗剂。SKF-38393（1μg/0.5μl生理盐水）用作D1样受体激动剂，喹吡罗（2μg/0.5μl生理盐水）用作D2样受体激动剂，SCH-23390（0.5μg/0.5μl生理盐水）用作D1样受体拮抗剂，舒必利（3μg/0.5μl二甲基亚砜）用作D2样受体拮抗剂。为了诱导口面部疼痛，将50μl 1%福尔马林皮下注射到上唇左侧。我们的结果表明，不同剂量的吗啡在福尔马林诱导的两个阶段均显著减轻了口面部疼痛。纳洛酮（1和3μg）在CA1中逆转了吗啡诱导的镇痛作用。SKF-38393和喹吡罗与纳洛酮（1μg）在两个阶段均显著减轻了福尔马林诱导的口面部疼痛。SCH-23390在口面部疼痛的两个阶段对吗啡的抗伤害感受反应均无影响。舒必利仅在第一阶段逆转了吗啡的抗伤害感受作用，但这一结果并不显著。我们的研究结果表明，阿片能系统与多巴胺能系统之间存在相互作用。阿片能神经元也通过调节大脑CA1区域的多巴胺能系统发挥抗伤害感受作用。
