中枢α_2-肾上腺素能受体对家兔脑室注射P物质所致升压反应的抑制作用

The Inhibitory Effect of Central Alpha 2 Adrenoceptors on the Pressor Response to Intracerebroventricular Injection of Substance P

将 Ｐ 物质（ｓｕｂｓｔａｎｃｅ Ｐ， Ｓ Ｐ，０ ．２０ ．９ ｎｇｋｇ） 注入家兔第四脑室（ｉｃｖ） 引起肺动脉压（ Ｐ Ａ Ｐ） 升高或降低，但以升压反应为主。与此同时，颈动脉压（ Ｃ Ａ Ｐ） 上升，心率（ Ｈ Ｒ） 减慢。若预先ｉｃｖ α２肾上腺素能受体阻断剂育亨宾（４５ μｇ） 可增强 Ｓ Ｐ 引起的肺动脉和颈动脉升压反应；预先ｉｃｖ α１肾上腺素能受体阻断剂哌唑嗪（１５ μｇ） 可阻断这两个升压反应，而普萘洛尔（１００ μｇ） 对这两个升压反应无明显影响。以上结果表明， Ｓ Ｐ 引起的肺动脉和颈动脉升压反应是由脑中的α１肾上腺素能受体介导的，而中枢α２肾上腺素能受体系统对传递 Ｓ Ｐ 中枢加压作用的路径有抑制性的调制作用。

Experiments were done in rabbits anaesthetized with urethane and im mobilized under artificial respiration . It wasfound thatsubstance P( S P,0 .20 .9 ngkg) injected into the 4th cerebroventricleinduced either a rise or a dropof pulmonary arterial pressure( P A P) with predominated pressor response . In addition , a rise in carotid arterialpressure( C A P) and reduction in heart rate( H R) were also observed . Pretreatment with prazosin ,an α1 adrenoceptorblocker,by intracerebroventricularinjection could block both the S P induced pulmonary and carotid pressor responses . Yohimbin, an α2 adrenoceptor blocker , could enhance the pressor responses in both arteries . Propranolol , a β adrenoceptor blocker,showed no effect on the pressorresponses to the central application of substance P. The resultsindicate that S P induced pulmonary and carotid pressor responses may be mediated by central α1 adrenoceptors , whilethe central α2 receptors exert an inhibitory modulation on the central S P induced pressor pathway .