自发性高血压大鼠主动脉压力感受性反射衰减的进一步研究

A Further Study on Attenuation of Aortic Baroreflex in Spontaneously Hypertensive Rats

目的 进一步探讨主动脉压力感受反射中枢性衰减在自发性高血压大鼠 ( SHR)发病中的作用及其发生机制。 方法 采用 6Hz与 60 Hz两种频率的电方波刺激主动脉神经 ,观察 SHR在高血压发生、发展中主动脉压力感受反射的变化。静注 M受体阻断剂观察其对主动脉压力感受性反射及其衰减的影响。 结果 ( 1) SHR收缩压自 8周龄起逐渐升高 ,16～ 32周龄稳定于高血压水平 ;心率在 4周龄时明显加快 ,左室重 /体重比值自 4周龄始逐渐升高。 ( 2 )静注阿托品减小两种频率刺激主动脉神经的反射效应 ,并使两种频率诱发的 HR与 MAP效应的差异分别被完全和部分消除。 ( 3)随血压升高 ,SHR的主动脉压力感受反射逐渐衰减 ,反射性 HR效应的衰减先于 MAP效应 ,有髓传入纤维反射效应的衰减先于无髓纤维。阿托品用药后 ,各周龄 SHR与 WKY大鼠的HR效应差异被消除 ,但 32周龄 SHR与 WKY大鼠的 MAP效应的差异仍存在。 结论 SHR主动脉压力感受反射的中枢性衰减在高血压的发展中起作用 ,高血压早期有髓纤维传入心率效应的衰减完全来源于心迷走中枢的机能变化 ,后期血压效应的衰减可能包括交感中枢的机能变化。

To study further on the role of central attenuation of aortic baroreflex during the development of hypertension and its mechanism \ Methods\ Changes in systolic blood pressure(SBP) and the ratio of LVM /BW were examined during development of hypertension in SHR and age matched WKY rats and the sensitivity of baroreflex was observed simultaneously by electrical stimulation of aortic nerve \ In the meantime,the effect of vagal blocking with atropine on aortic baroreflex was investigated \ Results\ (1)In SHR SBP elevated since the age of 8 wk and hypertension became to be established at the age of 16~32 wk,HR was elevated in SHR at the age of 4 wk,the ratio of LVM/BW was significantly higher in SHR after 4th week (2)Atropine i v decreased the reaction of aortic baroreflex and the difference of HR and MAP effect induced by two frequencies was eliminated completely or in part (3)With BP rising, the aortic baroreflex in SHR assumed progressive attenuation \ The attenuation of HR response was prior to depressor response and that of responses induced by myelinated fibers was prior to by unmyelinated fibers After atropine i v ,the difference of HR effect between SHR and WKY was eliminated \ However, difference of MAP effect between 32 week aged SHR and WKY still remained \ Conclusion\ The central attenuation of aortic baroreflex plays a role in the development of hypertension \ In early hypertension,the HR effect attenuation in myelinated fiber originates completely from functional changes in cardiac vagal center \ The attenuation of MAP effect at later stage can recover the functional changes in sympathetic nerve center \;