中缝大核对大鼠心脏伤害性感受的下行抑制性调控作用及其调控通路

Descending inhibitory modulation of nucleus raphes magnus in cardiac nociception in rats and its pathway

目的:观察大鼠心脏-躯体运动反射(CMR),阐明中缝大核(NRM)对大鼠心脏伤害性感受的下行抑制性调控作用及其调控通路。方法:34只雄性健康SD大鼠随机分为NRM电刺激组(n=8)、NRM电刺激联合脊髓背外侧束(DLF)横断组(n=8)和NRM电刺激联合5-羟色胺(5-HT)受体拮抗剂鞘内微注射组(n=18)。所有大鼠均采用心包插管术制作为CMR模型,以心包内注入致痛剂辣椒素(CAP)所诱发的背斜方肌肌电(EMG)为检测指标,通过NRM区域放置刺激电极和(或)脊髓鞘内置管的方法,观察NRM高强度电刺激对CMR的下行调控作用及双侧DLF横断和鞘内5-HT受体拮抗剂注射对NRM下行调控作用的影响。结果:给予NRM 75μA高强度电刺激后,CAP注射诱发的EMG反应与其未实施NRM电刺激前的基础对照比较明显减小(P<0.05);实施双侧DLF横断后,NRM高强度电刺激后的EMG反应明显大于DLF横断前(P<0.05),且与其基础对照比较差异无统计学意义(P>0.05);5-HT受体拮抗剂鞘内微注射后,NRM高强度电刺激后的EMG反应较鞘内注射前明显增加(P<0.05),但仍小于其基础对照(P<0.05)。结论:NRM高强度电刺激对心脏伤害性感受具有下行抑制性调控作用,其下行抑制性调控通路主要由DLF所介导,且脊髓内5-HT能神经系统可能参与了源自NRM的抑制性调控过程。

Objective To observe the cardiosomatic motor reflex （CMR）of rats, and to clarify the descending modulation of nucleus raphes magnus （NRM）in cardiac nociception and its pathway.Methods 34 male healthy SD rats were randomly divided into NRM electrical stimulation group （n=8 ）, NRM stimulation combined with dorsolateral funiculus （DLF ） transection group （n= 8 ）, NRM stimulation combined with antagonist of 5-hydroxytryptamine （5-HT）methysergide intrathecal administration group （n=18）.The rat model of CMR was established through inj ecting capsaicin into the pericardial sac of the rats in various groups. The electromyogram （EMG） response of dorsal spinotrapezius muscle was used as detection index, and by placing the stimulation electrode in NRM and （or）intrathecal catheterization, the descending inhibitory modulation of NRM in CMR and the influence of DLF tansection or methysergide intrathecal administration in descending inhibitory modulation of NRM were observed.Results Compared with before stimulation,the EMG response was decreased after NRM electrical stimulation （75 μA） （P〈0.05 ）;after bilateral DLF transection, the EMG response after NRM stimulation was significantly increased compared with before DLF transection （P〈0.05 ）, and there was no significant difference compared with its control （P〉 0.05 ）. In addition, after intrathecal administration of methysergide,the EMG response after NRM stimulation was significantly increased compared with before intrathecal treatment of methysergide （P〈0.05）,but it was still significantly smaller than that of its control （P〈0.05）. Conclusion Cardiac nociception evoked by capsaicin stimulation is subject to descending inhibitory modulation from NRM,and the descending inhibition from NRM is conveyed via the DLF and partially mediated by endogenous 5-HT system.