Park K H, Long J P
Department of Pharmacology, College of Medicine, University of Iowa, Iowa City.
J Pharmacol Exp Ther. 1991 Apr;257(1):50-5.
In anesthetized normotensive rats, 45 degrees head-up tilt induced a transient marked drop followed by a long-lasting slight drop in mean arterial pressure (MAP), and with cessation of tilt there is a transient pressor response. Heart rate (HR) did not change appreciably by tilting. Bilateral occlusion of common carotid arteries (BCO) induced pressor responses with tachycardia. Physostigmine (5 and 15 micrograms i.c.v.) attenuated the tilt-induced decreases in MAP. Neither the HR during tilt nor the restoration-related transient pressor response was altered by physostigmine. Acetylcholine (ACh, 5 micrograms i.c.v.) exhibited a similar attenuation of tilt-induced changes in MAP. Physostigmine enhanced BCO-induced pressor responses whereas not affecting BCO-induced HR responses. The time for onset of these changes in arterial pressure was slower than that of physostigmine-induced pressor response. Depletion of brain ACh with hemicholinium-3 (20 micrograms i.c.v.) or its derivative A-5 (20 micrograms i.c.v.) or blockade of muscarinic-receptors with atropine (1 microgram i.c.v.) blocked physostigmine-elicited modulation of both tilt- and BCO-induced reflexes. These results suggest involvement of central cholinergic systems for modulation not only of BCO-induced but also tilt-induced cardiovascular reflexes. In particular, ACh appears to enhance these reflexes by acting within the central nervous system.
在麻醉的正常血压大鼠中，头抬高45度会导致平均动脉压（MAP）先出现短暂的显著下降，随后是持续的轻微下降，停止倾斜时会出现短暂的升压反应。倾斜对心率（HR）没有明显影响。双侧颈总动脉闭塞（BCO）会引起伴有心动过速的升压反应。毒扁豆碱（脑室内注射5微克和15微克）可减弱倾斜引起的MAP下降。毒扁豆碱对倾斜期间的心率以及与恢复相关的短暂升压反应均无影响。乙酰胆碱（ACh，脑室内注射5微克）对倾斜引起的MAP变化也有类似的减弱作用。毒扁豆碱增强了BCO引起的升压反应，但不影响BCO引起的心率反应。这些动脉压变化的起效时间比毒扁豆碱引起的升压反应起效时间慢。用半胱氨酸-3（脑室内注射20微克）或其衍生物A-5（脑室内注射20微克）耗尽脑内乙酰胆碱，或用阿托品（脑室内注射1微克）阻断毒蕈碱受体，均可阻断毒扁豆碱对倾斜和BCO引起的反射的调节作用。这些结果表明，中枢胆碱能系统不仅参与调节BCO引起的心血管反射，也参与调节倾斜引起的心血管反射。特别是，乙酰胆碱似乎通过在中枢神经系统内起作用来增强这些反射。
