Persegol L, Palisses R, Viala D
Laboratoire de Neurophysiologie, Faculté des Sciences Mirande, Dijon, France.
Neuroscience. 1987 Nov;23(2):631-40. doi: 10.1016/0306-4522(87)90081-9.
The coordination of breathing activity with chest movements was compared in the same decorticate rabbit preparations prior to and after a transection at the C2 spinal level. Pharmacological activation was induced with a combination of nialamide and DOPA in the latter situation. The preparation was curarized and chest inflations and deflations were induced by a respirator whose parameters could be modified. In decorticate preparations, phrenic activity was coordinated 1:1 with the respirator period over a large range of imposed periods. Beyond the extreme values a new coupling was achieved with a ratio of either 1:2 or 2:1. Throughout the range of 1:1 coordination, phrenic bursting always happened at a preferred time in the respirator period, although this time differed for the various imposed periods. This coordinated activity required vagal inputs. After spinal transection the phrenic nerves were totally silent; DOPA administration allowed rhythmic activity to develop. In some preparations, phrenic bursts were coordinated 1:1 with the respirator period and remained so for all the imposed periods: the phase of these phrenic discharges relative to the respirator cycle was kept unchanged for the different periods. In addition, there was a modulation of amplitude superimposed on this 1:1 coupling. These spinal phrenic bursts were generally suppressed when the respirator was turned off. From these results, the coordination of phrenic activity with the respirator rate appears to be produced by different mechanisms in the decorticate and in the spinal preparations. In the decorticate animal the periodic vagal inflow reset the activity of the medullary inspiratory generator and entrains it at its own rate. The coordination observed in the spinal preparation results from a periodic peripheral activation of premotoneuronal or motoneural phrenic elements during inflation. If the central bursts provided by the spinal "respiration" generator can fire phrenic motoneurons above threshold, their timing is not dependent on the peripheral inflow; when the motoneurons are fired below threshold by these central inputs, they are probably summing together the central and peripheral excitations, which could account for the amplitude modulation of the coordinated phrenic bursts of pure reflex origin. Possible afferent pathways are discussed.
在C2脊髓水平横断前后，对同一去皮质兔制备物中呼吸活动与胸部运动的协调性进行了比较。在后一种情况下，用烟酰胺和多巴联合诱导药理学激活。制备物用箭毒麻痹，由参数可调节的呼吸器诱导胸部的充气和放气。在去皮质制备物中，在很大范围的设定周期内，膈神经活动与呼吸器周期以1:1的比例协调。超出极值时，会实现新的耦合，比例为1:2或2:1。在整个1:1协调范围内，膈神经爆发总是在呼吸器周期中的一个优选时间发生，尽管这个时间因不同的设定周期而异。这种协调活动需要迷走神经输入。脊髓横断后，膈神经完全沉默；给予多巴可使节律性活动发展。在一些制备物中，膈神经爆发与呼吸器周期以1:1的比例协调，并且在所有设定周期内都保持如此：这些膈神经放电相对于呼吸器周期的相位在不同周期保持不变。此外，在这种1:1耦合上叠加有幅度调制。当呼吸器关闭时，这些脊髓膈神经爆发通常会受到抑制。从这些结果来看，膈神经活动与呼吸频率的协调似乎是由去皮质和脊髓制备物中的不同机制产生的。在去皮质动物中，周期性的迷走神经传入重置了延髓吸气发生器的活动，并以其自身的速率使其同步。在脊髓制备物中观察到的协调是由充气期间运动前神经元或运动神经元膈神经元件的周期性外周激活引起的。如果脊髓“呼吸”发生器提供的中枢爆发能够使膈运动神经元放电超过阈值，那么它们的时间不依赖于外周传入；当这些中枢输入使运动神经元在阈值以下放电时，它们可能是将中枢和外周兴奋相加，这可以解释纯反射起源的协调膈神经爆发的幅度调制。讨论了可能的传入途径。
