下丘脑室旁核的I组促代谢型谷氨酸受体在压力感受性反射调节中的作用

Role of mGluRI of paraventricular nucleus in regulation of baroreflex in conscious rats

目的探讨下丘脑室旁核(PVN)内的Ⅰ组促代谢型谷氨酸受体(mGluRI)在压力感受性反射中枢调节中的作用。方法①在清醒自由活动大鼠中,用脑部微量透析法和高效液相色谱法测定静脉注射苯肾上腺素诱发压力感受性反射时的PVN区谷氨酸含量的变化;②用mGluRⅠ的阻断剂MCPG或激动剂ACPD直接灌流PVN区,同时诱发压力感受性反射,并观察血压和心率的变化。结果①静脉注射苯肾上腺素诱发压力感受性反射时,PVN内的谷氨酸含量迅速升高到基础水平的(384.82±91.77)%(P<0.01)。②PVN区灌流mGluRⅠ阻断剂MCPG(2.5mmol/L),同时诱发压力感受性反射,其血压升值明显减小(P<0.01),心率降值明显增大(P<0.05),导致压力感受性反射的敏感性(△HR/△MAP)明显增大(P<0.05)。③PVN区灌流mGluRⅠ激动剂ACPD(1mmol/L)同时诱发压力感受性反射,其血压升值明显增加(P<0.001),心率降值明显减小(P<0.001),导致压力感受性敏感性明显降低(P<0.05)。结论 PVN内的mGluRⅠ在压力感受性反射的中枢调节中起抑制作用。

[Objective] To investigate the possible involvement of group I metabotropic glutamate receptors （mGluRⅠ） in the hypothalamic paraventricular nucleus （PVN） in the central regulation of baroreflex.[Methods] The baroreflex was induced by intravenous injection of phenylephrine. Then the extracellular concentration of glutamate （Glu） in the PVN region was measured by microdialysis and high performance liquid chromatography （HPLC） techniques, and blood pressure （BP） and heart rate （HR） were recorded in conscious rats. To determine whether the mGluRI was involved in the regulation of baroreflex, MCPG （an antagonist of mGluRⅠ） or ACPD （an agonist of mGluRⅠ） was directly perfused in the PVN region during baroreflex. [Results]During baroreflex, the concentration of Glu in the PVN region was immediately increased to （384.82±91.77）% of basal level （P 0.05）; ② During baroreflex, direct perfusion of MCPG （2.5 mmol/L） in the PVN attenuated the increase of BP （P 0.05） and enhanced the reduced response of HR （P 0.05）, resulting in significant increase of baroreflex sensitivity （P 0.05）. ③ During baroreflex, direct perfusion of ACPD （1 mmol/L） in the PVN enhanced the increase of BP （P 0.001） and attenuated the reduced response of HR （P 0.001）, resulting in significant decrease of baroreflex sensitivity （P 0.05）.[Conclusion]mGluRI in the PVN may produce an inhibitive effect on baroreflex.