延髓腹外侧区微量注射L－NNA和SNP对大鼠血压、心率和肾交感神经活动的影响

在麻醉大鼠观察了向延髓腹外侧区微量注射ＮＯ合成酶抑制剂Ｎ－硝基左旋精氨酸（ＬＮＮＡ）和硝普钢（ＳＮＰ）对血压、心率和肾交感神经活动的影响，旨在探讨中枢左旋精氨酸－ＮＯ通路在动脉血压调节中的作用及其机制。实验结果如下：（１）向延髓腹外侧头端区（ＲＶＬＭ）注射Ｌ－ＮＮＡ后，平均动脉压（ＭＡＰ）升高，肾交感神经活动（ＲＳＮＡ）增强；心率（ＨＲ）减慢，但无统计学意义。ＭＡＰ和ＲＳＮＡ的变化持续３０ｍｉｎ以上；此效应可被预先静注左旋精氨酸所逆转。（２）向ＲＶＬＭ微量注射ＳＮＰ，ＭＡＰ降低，ＲＳＮＡ减弱；但ＨＲ的变化无统计学意义。（３）向延髓腹外侧尾端区（ＣＶＬＭ）注射Ｌ－ＮＮＡ，ＭＡＰ降低，ＨＲ减慢，ＲＳＮＡ减弱。（４）向ＣＶＬＭ微量注射ＳＮＰ，ＭＡＰ升高，ＲＳＮＡ增强，而心率无明显变化。以上结果表明，中枢左旋精氨酸－ＮＯ通路对延髓腹外侧部的神经元活动有调变作用。

EFFECTS OF MICROINJECTION OF L-NNA AND SNP INTO VENTROLATERAL MEDULLA ON BLOOD PRESSURE,HEART RATE AND RENAL SYMPATHETIC NERVE ACTIVITY IN RATS

The effects of microinjection of a NO synthase inhibitor- N-nitro-L-arginine (L-NNA) and NO donor-sodium nitroprusside (SNP) into ventrolateral medulla on blood pressure (BP), heart rate (HR) and renal sympathetic nerve activity (RSNA)were examined in anesthetized rats to define the role of L-arginine: NO pathway in the central regulation of BP and to explore the underlying mechanism. The results obtained were as follows: (1 ) Following microinjection of L-NNA into rostral ventrolateral medulla (RVLM), both of MAP and RSNA were increased. The effects lasted for more than 30 min and could be reversed by prior intravenous injection of L-arginine.(2) In response to microinjection of SNP into RVLM, MAP and RSNA were decreased, while HR showed no significant change. (3) During microinjection of L-NNA into caudal ventrolateral medulla (CVLM), MAP, HR and RSNA were decreased.(4) Upon injection of SNP into CVLM, MAP and RSNA were increased, but HR showed no significant change. The above-mentioned results indicate that the L-arginine : NO pathway may exhibit a modulatory action on the activity of ventrolateral medulla neurons.