Physician Assistant Studies Program, School of Health Professions, St. Bonaventure University, St. Bonaventure, New York.
Adv Physiol Educ. 2022 Dec 1;46(4):658-666. doi: 10.1152/advan.00095.2022. Epub 2022 Oct 6.
The frog sciatic nerve provides a robust physiological preparation students may conveniently use to investigate the properties of compound action potentials. Electrical stimulation with standard physiology teaching equipment elicits compound action potentials that are easily recorded by upper-level undergraduate students. The amplitude of compound action potentials increases with greater stimulation voltages, up until a maximum response is achieved. Plotting action potential size as a function of stimulating voltage produces a curve that illustrates the responsiveness of a nerve. In the present study, several local anesthetics (MS-222, procaine, lidocaine, benzocaine, and tetracaine) were used to reversibly suppress compound action potentials within a time frame consistent with the limitations of teaching labs. Highly responsive nerves generate steep response curves that reach asymptotes at relatively low stimulating voltages. Less active nerves require higher stimulating voltages and appear "right-shifted." Anesthetized response curves may also appear "flatter," exhibiting lower peak amplitude, when compared to fully active nerves. The magnitude of action potential suppression and time course of recovery depended upon the specific anesthetic applied. Nerves anesthetized with MS-222 were the fastest to recover, reaching their original responsiveness within 20 min. Tetracaine had the most dramatic effects, with nerves typically requiring more than a day to fully recover physiological responses. Carefully dissected nerves maintained their physiological responses for many days when stored in Ringer solution at 4°C, making this preparation particularly useful for undergraduate lab experiences. Quantitative analyses may be performed on the data collected, providing students with opportunities to design and implement their own experiments. The frog sciatic nerve preparation represents a "classical" physiology lab for demonstrating principles of action potentials. Local anesthetics provide an inexpensive tool to manipulate the physiological activity of nerves and other excitable tissues. Isolated nerves retain their physiological activity for up to several days when kept in Ringer solution at 4°C. Quantitative data analysis from this robust nerve preparation should present students with many opportunities for designing their own experiments with anesthetics.
青蛙坐骨神经为学生提供了一个强大的生理准备，可以方便地用于研究复合动作电位的特性。使用标准生理学教学设备进行电刺激会引发复合动作电位，这些电位很容易被高年级本科生记录下来。复合动作电位的幅度随着刺激电压的增加而增加，直到达到最大响应。将动作电位大小作为刺激电压的函数绘制曲线，可以说明神经的反应性。在本研究中，几种局部麻醉剂（MS-222、普鲁卡因、利多卡因、苯佐卡因和四卡因）被用于在与教学实验室限制一致的时间框架内可逆地抑制复合动作电位。高度敏感的神经产生陡峭的响应曲线，在相对较低的刺激电压下达到渐近线。不活跃的神经需要更高的刺激电压，表现为“右移”。与完全活跃的神经相比，麻醉后的响应曲线可能显得“更平坦”，峰值幅度较低。动作电位抑制的幅度和恢复时间取决于所应用的特定麻醉剂。用 MS-222 麻醉的神经恢复最快，在 20 分钟内恢复到原来的反应性。四卡因的影响最为显著，神经通常需要一天以上才能完全恢复生理反应。在 4°C 的 Ringer 溶液中精心解剖的神经可以保持其生理反应数天，这使得这种准备特别适用于本科实验室经验。可以对收集的数据进行定量分析，为学生提供设计和实施自己实验的机会。青蛙坐骨神经制备物代表了用于演示动作电位原理的“经典”生理学实验室。局部麻醉剂提供了一种廉价的工具，可以操纵神经和其他可兴奋组织的生理活性。在 4°C 的 Ringer 溶液中保存时，分离的神经可以保持其生理活性长达数天。来自这种强大神经制备物的定量数据分析应该为学生提供许多机会，让他们用麻醉剂设计自己的实验。
