刺激兔下丘脑对心肌局部血流量和脊髓中间外侧柱P物质含量的影响

本工作在48只氯醛糖-尿酯混合液静脉麻醉,三碘季铵酚制动,人工呼吸,切断两侧迷走神经,并静脉注射心得安(15mg/kg)阻断 β 受体的兔上进行。实验结果显示:1.电刺激下丘脑背内侧核(DMH),可观察到平均动脉血压(MABP)增加,心率无明显变化。用放射性生物微球技术测定心肌局部血流量(RMBF),看到刺激左侧或右侧 DMH 均使左室 RMBF 明显减少,前者减少20.9%,而后者减少13.2%,两者相比差异有显著性(p<0.05),但右室RMBF 改变不明显。2.左侧或右侧 DMH 刺激使左室前壁心外膜电图(EECG)ST 段明显抬高,EECG-ST 段变化与 RMBF 呈负相关(r=-0.825,p<0.01),但与血压变化呈非线性相关(r=0.347,p=0.159)3.用放射免疫测定技术(RIA)测定脊髓胸2-5(T_(2-5))节段中间外侧柱(IML)中 P 物质(SP)含量,观察到在刺激 DMH 诱发心肌缺血的动物中,两侧IML 内 SP 的含量均显著减少,以刺激的同侧 IML 时变化更明显。上述结果提示:下丘脑背内侧核兴奋可诱发冠状动脉痉挛,心肌局部血流量减少,其中枢机理可能与脊髓 IML 部位 SP 释放,诱发交感缩冠脉作用有关。

EFFECT OF HYPOTHALAMIC STIMULATION ON RMBF AND SP CONTENT IN IML OF SPINAL CORD IN RABBITS

Experlments were performed on 48 urethane-chloralose anaesthetized,gal-lamine triethiodide immobilized and vagotomized rabbits under artificial ventila-tion.Radiolabeled microspheres were injected into the left atrium during stim-ulation of the left or right dorsomedial hypothalamic nucleus(LDMH or RDMH)to measure regional myocardial blood flow(RMBF).RDMH stimulation pro-duced relatively little flow reduction of the left ventricle,whereas LDMH stimula-tion produced an obvious flow reduction.No significant change occurred in theright ventricle.Meanwhile,LDMH or RDMH stimulation caused increases ofmean arterial blood pressure(MABP)and changes of epicardial electrogram(EECG)ST segment,but no significant changes in heart rate.EECG ST segment was ele-vated in relation to the reduction of RMBF in left ventricle(r=-0.825,P<0.001).Linear regression analysis of MABP change in relation to left ventricle RMBF show-ed no significant correlation.In intact rabbits,it was demonstrated that DMHstimulation caused an decrease of substance P(SP)immunoreactive material inbilateral intermediolateral cell columns(IML)of T_(2-5)spinal cord concomitantlywith an elevation,in MABP and EECG ST changes.The results suggest that electrical stimulation of DMH can elicit coronaryconstriction,decrease in RMBF,elevation of EECG ST segment and increase inMABP,which may be mediated by the release of SP immunoreactive material inthe IML of the spinal cord.