Intercostal expiratory activity in an in vitro brainstem-spinal cord-rib preparation from the neonatal rat
Intercostal expiratory activity in an in vitro brainstem-spinal cord-rib preparation from the neonatal rat
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DOI：
10.1111/j.1469-7793.1999.00293.x
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发表时间：
1999-10-01
影响因子：
5.5
通讯作者：
Iizuka, M
中科院分区：
文献类型：
--
作者：
Iizuka, M
1.我们研究了是否可以观察到呼气活动时，中央化学感受器被激活的细胞外pH值的递减在一个孤立的脑干脊髓肋骨制备0至3日龄大鼠。呼气活动被定义为在C4腹根（包含膈运动轴突）周期性吸气爆发之间的沉默期内发生在内部肋间肌（IIM）中的爆发活动。在用改良Krebs液（26marHCO_3-，5%CO_2，pH7.4）灌流时，尽管C_4前根总是出现节律性吸气运动，但IIM没有一致的活动。当通过将[HCO 3-]从26 mM降低到10 mM而将灌注液的pH从约7.4降低到7.1时，C4吸气节律的频率增加，并且在IIM中出现节律性活动。在大多数情况下，IIM的节律爆发开始后，停止C4吸气爆发，并符合运动的肋骨在尾部方向。这种肋间呼气爆发仅限于呼气相的前半部分。当灌流液中加入甘氨酸受体拮抗剂士的宁（5-10 μ M）时，C4前根和IIM之间的协调相互运动活动变为一种很大程度上重叠的模式。这些结果表明（i）负责呼气运动活动的神经元机制在这种体外制备中得以保留，以及（ii）甘氨酸能抑制系统在呼吸期间吸气和呼气运动活动之间的协调中起重要作用。
1. We examined whether expiratory activity can be observed when central chemoreceptors are activated by a decrement in the extracellular pH in an isolated brainstem-spinal cord-rib preparation from 0- to 3-day-old rats. Expiratory activity was defined as the burst activity that occurs in an internal intercostal muscle (IIM) during the silent period between the periodic inspiratory bursts in the C4 ventral root (which contains phrenic motor axons).2. During perfusion with modified Krebs solution (26 mar HCO3-, 5% CO2, pH 7.4), there was no consistent activity in IIM, though rhythmic inspiratory motor activity always appeared in the C4 ventral root.3. When the pH of the perfusate was lowered from about 7.4 to 7.1 by reducing [HCO3-] from 26 to 10 mM, the frequency of the C4 inspiratory rhythm increased, and rhythmic activity appeared in IIM. In most cases, the rhythmic burst in IIM started just after the cessation of the C4 inspiratory burst and coincided with movement of the ribs in a caudal direction. This intercostal expiratory burst was limited to the first half of the expiratory phase.4. The coordinated reciprocal motor activity between the C4 ventral root and IIM changed to a largely overlapping pattern when strychnine (5-10 mu M), a glycine receptor antagonist, was added to the perfusate.5. These results suggest (i) that the neuronal mechanisms responsible for expiratory motor activity are preserved in this in vitro preparation and (ii) that the glycinergic inhibitory system plays an important role in the coordination between inspiratory and expiratory motor activity during respiration.