Cheeseman M, Revelette W R
Department of Physiology and Biophysics, University of Kentucky, Lexington 40536-0084.
J Appl Physiol (1985). 1990 Aug;69(2):640-7. doi: 10.1152/jappl.1990.69.2.640.
Recent evidence from several laboratories suggests that activation of afferents in the diaphragm can reflexly affect inspiratory muscle activation. This study determined whether afferents in the diaphragm contribute to compensatory changes in phrenic motor drive when the operating length of the diaphragm is suddenly increased. Experiments were performed in six closed-chest pentothal-anesthetized cats. Length changes were measured using a pair of piezoelectric crystals implanted in the left crural diaphragm. The crural electromyogram (EMGdi) was measured by electrodes fixed to each crystal. The animal was suspended in a spinal frame, and a Plexiglas tube was fitted around the cat's abdomen. A balloon placed inside the tube was inflated during the expiratory phase to produce a mean increase of 17% in diaphragm length at functional residual capacity. Ten trials were performed in succession under the following conditions: intact, after bilateral vagotomy, after spinal section at C7, and after cervical dorsal rhizotomy. Peak integrated EMGdi (integral of EMGdi) and neural inspiratory time (nTI) were measured for the last control inspiration and the first after inflation. There was a significant reduction in the peak integral of EMGdi when the length of the diaphragm was increased for all conditions except after rhizotomy. Although not measured, it is likely that the tension developed by the diaphragm was also increased during abdominal compression. Results suggest that afferents sensitive to changes in the operating length and/or tension in the diaphragm contribute to compensatory alterations in phrenic motor drive.
来自多个实验室的最新证据表明，膈肌传入神经的激活可反射性地影响吸气肌的激活。本研究旨在确定当膈肌的工作长度突然增加时，膈肌传入神经是否会对膈神经运动驱动的代偿性变化产生影响。实验在六只戊巴比妥钠麻醉的开胸猫身上进行。使用植入左侧膈肌脚的一对压电晶体测量长度变化。通过固定在每个晶体上的电极测量膈肌脚肌电图（EMGdi）。将动物悬吊在脊柱固定架上，在猫的腹部周围安装一个有机玻璃管。在呼气期向管内放置的气球充气，以使功能残气量时膈肌长度平均增加17%。在以下条件下连续进行十次试验：完整状态、双侧迷走神经切断术后、C7脊髓横断术后以及颈背根切断术后。测量最后一次对照吸气和充气后第一次吸气时的EMGdi峰值积分（EMGdi积分）和神经吸气时间（nTI）。除根切断术后外，在所有条件下，当膈肌长度增加时，EMGdi峰值积分均显著降低。虽然未进行测量，但在腹部加压过程中膈肌产生的张力可能也会增加。结果表明，对膈肌工作长度和/或张力变化敏感的传入神经有助于膈神经运动驱动的代偿性改变。
