Saleh T M, Connell B J
Department of Anatomy and Physiology, Atlantic Veterinary College, University of Prince Edward Island, Charlottetown, Canada.
Brain Res. 1997 Sep 5;767(2):201-7. doi: 10.1016/s0006-8993(97)00560-x.
The parabrachial nucleus (PBN) has a prominent anatomical connection with the nucleus of the solitary tract as well as other central baroreflex centres which suggests a role for the PBN in the regulation of this cardiovascular reflex. This study examined the effects of a reversible, bilateral blockade of the PBN on the cardiac baroreflex. Male Sprague-Dawley rats were anesthetized with sodium butabarbitol and instrumented to monitor blood pressure and heart rate and for the intravenous administration of drugs. The cardiac baroreflex was evoked using bolus intravenous injections of phenylephrine (PE) and sodium nitroprusside (NaNp) at various doses and a graph of baroreflex sensitivity was constructed. Bilateral microinjections of the reversible anesthetic, lidocaine (5%, 300 nl), into the PBN did not significantly change baseline blood pressure or heart rate when compared to microinjections of saline (0.9%, 300 nl) into the PBN. The pressor or depressor responses evoked by bolus injections of PE or NaNp, respectively, were not significantly affected by the bilateral pretreatment of the PBN with lidocaine when compared to saline controls. However, approximately 30 min following lidocaine injection, the amplitudes of both the evoked-reflex bradycardia and reflex tachycardia were significantly increased by approximately 98%. The cardiovascular responses to various doses of PE and NaNp were graphed and baroreflex sensitivity curves were constructed. This graph showed an increased slope of the baroreflex sensitivity curve following lesions of the PBN. Reflex changes in heart rate returned to pre-lidocaine injection levels after approximately 2 h. The results of the present investigation suggest that the PBN participates in the modulation of the cardiac baroreflex which in turn suggests a role for this nucleus in the central integration of cardiovascular reflex function.
臂旁核（PBN）与孤束核以及其他中枢压力反射中枢有着显著的解剖学联系，这表明PBN在调节这种心血管反射中发挥作用。本研究考察了PBN可逆性双侧阻断对心脏压力反射的影响。雄性Sprague-Dawley大鼠用丁巴比妥钠麻醉，并安装监测血压和心率的仪器以及用于静脉给药的装置。通过静脉推注不同剂量的去氧肾上腺素（PE）和硝普钠（NaNp）诱发心脏压力反射，并绘制压力反射敏感性曲线。与向PBN内微量注射生理盐水（0.9%，300 nl）相比，向PBN内双侧微量注射可逆性麻醉剂利多卡因（5%，300 nl）并未显著改变基线血压或心率。与生理盐水对照组相比，PBN双侧用利多卡因预处理后，分别由PE或NaNp推注诱发的升压或降压反应未受到显著影响。然而，在注射利多卡因后约30分钟，诱发的反射性心动过缓和反射性心动过速的幅度均显著增加了约98%。绘制了对不同剂量PE和NaNp的心血管反应图，并构建了压力反射敏感性曲线。该图显示PBN损伤后压力反射敏感性曲线的斜率增加。大约2小时后，心率的反射性变化恢复到注射利多卡因前的水平。本研究结果表明，PBN参与心脏压力反射的调节，这反过来表明该核在心血管反射功能的中枢整合中发挥作用。
