Mitra J, Dev N B, Trivedi R, Amini S, Ernsberger P, Cherniack N S
Department of Biometry, Case Western Reserve University School of Medicine, Cleveland, Ohio 44106.
Respir Physiol. 1993 Jul;93(1):71-82. doi: 10.1016/0034-5687(93)90069-m.
To examine the effect of hypoxia confined to the ventrolateral medulla we microinjected NaCN into the cat medulla (1.0 mm below the ventral surface) unilaterally and investigated cardio-respiratory changes. We studied anesthetized artificially ventilated animals and measured the electrical activity of phrenic and cervical sympathetic nerves and blood pressure. Histotoxic hypoxia depressed phrenic amplitude and elevated sympathetic tone and blood pressure. These responses were obtained predominantly from the region 5.0-8.0 mm caudal to the foramen caecum and 3.0-5.0 mm lateral to the midline (intermediate area). A study with 14C-cyanide showed that total and covalently bound cyanide was confined within a 1 mm diffusion sphere following microinjection. Isolated areas in both rostral and caudal medulla responded to cyanide with elevated sympathetic tone in the absence of phrenic nerve depression, suggesting dissociation of respiratory and vasomotor responses to hypoxia. Thus, the respiratory depression and vasomotor excitation produced by central hypoxia can be reproduced by hypoxia limited to discrete regions of the ventrolateral medulla.
为了研究局限于延髓腹外侧的低氧效应，我们将氰化钠单侧微量注射到猫的延髓（腹侧表面以下1.0毫米处），并研究心肺变化。我们研究了人工通气的麻醉动物，测量了膈神经和颈交感神经的电活动以及血压。组织中毒性低氧降低了膈神经振幅，提高了交感神经张力和血压。这些反应主要来自盲孔尾侧5.0 - 8.0毫米和中线外侧3.0 - 5.0毫米的区域（中间区域）。一项用¹⁴C - 氰化物进行的研究表明，微量注射后，总氰化物和共价结合的氰化物局限在1毫米的扩散球内。在没有膈神经抑制的情况下，延髓头端和尾端的孤立区域对氰化物的反应是交感神经张力升高，这表明对低氧的呼吸和血管运动反应存在分离。因此，中枢性低氧产生的呼吸抑制和血管运动兴奋可以通过局限于延髓腹外侧离散区域的低氧来重现。
