Department of Physiology, Harbin Medical University, Xuefu Road, No.194, Harbin 150081, People's Republic of China.
Neurochem Res. 2012 May;37(5):977-82. doi: 10.1007/s11064-011-0690-0. Epub 2012 Jan 13.
Morphine is among the most effective analgesics. However, many evidences suggest that, besides the well-know analgesic activity, repeated opioids treatment can induce some side effects such as dependence, hyperalgesia and tolerance. The mechanism of noxious information transmission in the central nervous system after dependence is not clear. An important neurotransmitter, dopamine (DA) participates not only in the process of opioid dependence but also in pain modulation in the central nervous system. In the present study we observed changes of electrical activities of pain-excitation neurons (PENs) and pain-inhibition neurons (PINs) in the caudate nucleus (Cd) following the development of morphine dependence. We also observed the role of DA on these changes. Our results revealed that both the latency of PEN discharges and the inhibitory duration of PIN discharges decreased, and the net increased values of PEN and PIN discharges increased in the Cd of morphine dependent rats. Those demonstrated that electrical activities of both PENs and PINs increased in morphine dependent rats. DA inhibited the electrical activities of PENs and enhanced those of PINs in morphine dependent rats.
吗啡是最有效的镇痛药之一。然而，许多证据表明，除了众所周知的镇痛作用外，反复使用阿片类药物治疗会引起一些副作用，如依赖、痛觉过敏和耐受。依赖后中枢神经系统中有害信息传递的机制尚不清楚。多巴胺（DA）是一种重要的神经递质，不仅参与阿片类药物依赖过程，也参与中枢神经系统的疼痛调节。在本研究中，我们观察了吗啡依赖发展过程中尾状核（Cd）中痛兴奋神经元（PENs）和痛抑制神经元（PINs）电活动的变化，以及 DA 在这些变化中的作用。结果表明，吗啡依赖大鼠 Cd 中 PEN 放电潜伏期和 PIN 放电抑制持续时间缩短，PEN 和 PIN 放电净增加值增加，表明吗啡依赖大鼠 PEN 和 PIN 电活动均增加。DA 抑制吗啡依赖大鼠 PEN 的电活动，并增强其 PIN 的电活动。
