Department of Physiology, Laboratory of Neural Electrophysiology, Harbin Medical University, 150081 Harbin, Heilongjiang, People's Republic of China.
Neurochem Res. 2012 Feb;37(2):428-35. doi: 10.1007/s11064-011-0629-5. Epub 2011 Oct 14.
Dopamine regulates pain perception in some areas of the central nervous system. Previously, we have confirmed that dopamine potentiated the electric activities of the evoked discharges of pain-excited neurons (PENs) and inhibited those of pain-inhibited neurons (PINs) in the parafascicular nucleus (Pfn) of normal rats. The mechanism of action of dopamine on pain-related neurons in the Pfn of morphine-dependent rat is still unknown. The present study aimed to determine the effects of dopamine and its receptor antagonist droperidol on the pain-evoked responses of the PEN and PIN in the Pfn of morphine-dependent rats, and to compare the effects between the morphine-dependent rat and the normal rat. The trains of electric impulses applied to the sciatic nerve were used as noxious stimulation. The discharges of PEN or PIN in the Pfn were recorded by using a glass microelectrode. The results showed that intra-Pfn microinjection of dopamine decreased the frequency of noxious stimulation-induced discharges of PEN and increased the frequency of PIN. The intra-Pfn administration of droperidol produced an opposite effect. These results demonstrated that dopamine is involved in nociceptive modulation in the morphine-dependent rat, the responses to noxious stimulation between normal rat and morphine-dependent rat are completely opposite. The effect of dopamine is through the dopamine D(2) receptor of PENs and PINs in Pfn. The results suggest that the dopamine system of the Pfn may become a therapeutic target for analgesia and the treatment of morphine dependence.
多巴胺在中枢神经系统的某些区域调节疼痛感知。此前，我们已经证实，多巴胺增强了正常大鼠臂旁核（Pfn）中痛觉兴奋神经元（PENs）的诱发放电活动，抑制了痛觉抑制神经元（PINs）的放电活动。吗啡依赖大鼠 Pfn 中与疼痛相关神经元的多巴胺作用机制尚不清楚。本研究旨在确定多巴胺及其受体拮抗剂氟哌啶醇对吗啡依赖大鼠 Pfn 中 PEN 和 PIN 对疼痛诱发反应的影响，并比较吗啡依赖大鼠与正常大鼠之间的影响。坐骨神经施加的电脉冲串用作伤害性刺激。通过使用玻璃微电极记录 Pfn 中 PEN 或 PIN 的放电。结果表明，Pfn 内微注射多巴胺降低了伤害性刺激诱导的 PEN 放电频率，增加了 PIN 放电频率。Pfn 内给予氟哌啶醇产生相反的效果。这些结果表明，多巴胺参与吗啡依赖大鼠的伤害性调制，正常大鼠和吗啡依赖大鼠对伤害性刺激的反应完全相反。多巴胺的作用是通过 PENs 和 Pfn 中的 PINs 的多巴胺 D2 受体。研究结果表明，臂旁核的多巴胺系统可能成为镇痛和治疗吗啡依赖的治疗靶点。
