电刺激中脑导水管周围灰质对大鼠心脏伤害性感受的下行性抑制调控

摘要

Objective To explore the descending inhibitory effect of periaqueductal gray(PAG)electrical stimulation on the cardiac nociception in rats. Methods Thirty-six male SD rats aged 10 weeks were randomly divided into three groups:normal saline group, bradykinin(BK)group,electrical stimulation plus BK group(n=12 in each group). A silicone catheter was inserted into the pericar-dial sac in each group. The rats were injected with saline(0.2 ml)into the pericardial sac in normal saline group,BK(0.2 ml)in BK group,and BK(0.2 ml)combined with PAG electrical stimulation in electrical stimulation plus BK group. The electromyogram(EMG) responses of dorsal spinotrapezius muscle were recorded to observe the changes of the cardiac somatic motor reflex induced by BK. The c-Fos expression in the spinal dorsal horn was detected. Results The intrapericardial BK induced EMG responses,and the responses were reliable and repeatable. When BK was injected into pericardial sac five times every 40 min,EMG responses in turn were 100%± 0.00%,98.75%± 0.75%,97.94%± 0.56%,97.11%± 0.52% and 96.63%± 0.68%;meanwhile,the c-Fos expression significant-ly increased in the spinal dorsal horn(P<0.05). Compared with BK group,the PAG electrical stimulation(100,150,200 μA)in-hibited EMG responses induced by BK in pericardial sac in electrical stimulation plus BK group,and EMG was reduced to 50.63%± 1.52%,43.27%± 1.99%,28.88%± 0.97%,respectively,and c-Fos expression decreased in the spinal dorsal horn(P<0.05). Conclusion Electrical stimulation in PAG can produce the descending inhibition on the cardic nociception in rats.%目的 观察电刺激中脑导水管周围灰质(periaqueductal gray,PAG)对大鼠心脏伤害性感受的下行性调控作用. 方法36只雄性10周龄SD大鼠随机分为3组:生理盐水组、缓激肽组、电刺激+缓激肽组,每组12只.各组大鼠均行心包内插管,生理盐水组心包内注射0.2 ml无菌生理盐水;缓激肽组心包内注射0.2 ml缓激肽;电刺激+缓激肽组心包内注射0.2 ml缓激肽联合PAG电刺激.观察心包内缓激肽诱发大鼠心脏-躯体运动反射的变化,该反射以背斜方肌肌电(electromyogram, EMG)为观测指标;同时观察脊髓背角c-Fos的表达. 结果 与生理盐水组相比,心包内注射缓激肽诱发了背斜方肌EMG活动,且心包内注射缓激肽诱发的EMG反应具有可靠的重复性,大鼠心包内各间隔40 min连续5次注射缓激肽,EMG反应依次为100%± 0.00%,98.75%± 0.75%,97.94%± 0.56%,97.11%± 0.52%,96.63%± 0.68%;同时,脊髓背角c-Fos表达显著增多(P<0.05).与缓激肽组相比,电刺激+缓激肽组电刺激PAG(100,150,200 μA)强度依赖性抑制了心包内缓激肽诱发的EMG活动,EMG分别下降至50.63%± 1.52%,43.27%± 1.99%和28.88%± 0.97%;同时,脊髓背角 c-Fos表达减少(P <0.05). 结论 电刺激PAG对大鼠心脏伤害性感受发挥了下行性抑制调控作用.