下丘脑前核微量注射褪黑素及其受体拮抗剂对大鼠血压和心率的影响

目的：研究下丘脑前核微量注射褪黑素及其受体拮抗剂对正常血压和应激性高血压大鼠心血管活动的影响。方法：微量注射褪黑色及其受体拮抗剂至下丘脑前区前核，记录血压、平均动脉压和心率。结果：微量注射褪黑素可降低平均动脉压，其竞争性ML1受体拮抗剂luzindole可完全阻断褪黑素的降压反应，而其ML2受体拮抗剂prazosin不能阻断褪黑素的降压反应。结论：褪黑素为一种降压因子，其降压反应主要通过激活ML1受体，而不是ML2受体来介导的。下丘脑前核是褪黑素影响心血管活动的重要中枢闰。

Effects of microinjection of melatonin and its receptor antagonists into anterior hypothalamic area on blood pressure and heart rate in rats

ABM:To examine the effects of microinjection of melatonin and its receptor antagonists into the anterior hypothalamic area (AHA) on blood pressure (BP) and heart rate (HR) in normotensive and stress-induced hypertensive rats. METHODS: Melatonin and its receptor antagonists were microinjected into the AHA, then BP, mean arterial pressure (MAP), and HR were synchronously recorded. RESULTS: Microinjection of melatonin produced a fall in MAP. Prazosin, an antagonist of melatonin ML2 receptor, could not antagonize the depressive response induced by melatonin. While luzindole, a competitive antagonist of melatonin ML1 receptor, was able to almost completely prevented the depressive response induced by injection of melatonin. CONCLUSION: Melatonin acts as a hypotensive factor and the effects are mainly due to activation of ML1 receptors in rat brain, and the AHA may be one of the important central areas where melatonin can exert modulatory effects on BP and HR.