Opioid-resistant respiratory pathway from the preinspiratory neurones to abdominal muscles:: in vivo and in vitro study in the newborn rat
Opioid-resistant respiratory pathway from the preinspiratory neurones to abdominal muscles:: in vivo and in vitro study in the newborn rat
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DOI：
10.1113/jphysiol.2002.023408
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发表时间：
2002-12-15
影响因子：
5.5
通讯作者：
Feldman, JL
中科院分区：
文献类型：
--
作者：
Janczewski, WA;Onimaru, H;Feldman, JL
我们报道，在给新生大鼠注射阿片类药物(阿片类药物引起的呼吸暂停)后，自主呼吸运动停止后，腹肌继续以与呼吸期观察到的相似的速度收缩。相应地，体外应用Mu阿片受体激动剂可以抑制供应横隔肌的第四颈根(C4)的活动，但不抑制支配腹肌的第一腰根(L1)的节律性活动。这表明存在抗阿片类药物的节律性神经元和将其活动传递到腹部运动神经元的神经通路。我们用新生大鼠的脑干-脊髓标本研究了这一途径。我们鉴定出球脊髓神经元的放电模式与L1根的相同。这些神经元位于OBEX的尾侧，位于疑核后附近。静息电位范围-49~-40 mV(平均+/-S.D.-44.0+/-4.3 mV)。平均输入电阻为315.5+/-54.8MOmega。L1水平的平均逆行潜伏期为42.8+/-4.4ms。轴突在细胞体水平穿过中线。球脊髓神经元和L1神经根的活动模式是每个呼吸周期有两次爆发，在吸气时有一段静默期。这种模式是吸气前神经元的特征。我们发现，11%的吸气前神经元投射到球脊髓神经元所在的区域。这些吸气前神经元位于延髓头端腹外侧，靠近腹面(200-350微米)，位于面后核的头端半侧水平。我们的数据表明，在体外准备过程中，存在从吸气前神经元到L1运动神经元的双突触通路。我们认为，在阿片类药物诱导的新生大鼠呼吸暂停过程中，同样的途径负责腹肌的节律性激活。
We report that after spontaneous breathing movements are stopped by administration of opioids (opioid-induced apnoea) in neonatal rats, abdominal muscles continue to contract at a rate similar to that observed during periods of ventilation. Correspondingly, in vitro bath application of a mu opioid receptor agonist suppresses the activity of the fourth cervical root (C4) supplying the diaphragm, but not the rhythmic activity of the first lumbar root (L1) innervating the abdominal muscles. This indicates the existence of opioid-resistant rhythmogenic neurones and a neuronal pathway transmitting their activity to the abdominal motoneurones. We have investigated this pathway by using a brainstem-spinal cord preparation of the neonatal rat. We identified bulbospinal neurones with a firing pattern identical to that of the L1 root. These neurones were located caudal to the obex in the vicinity of the nucleus retroambiguus. Resting potentials ranged from -49 to -40 mV (mean +/- S.D. -44.0 +/- 4.3 mV). The mean input resistance was 315.5 +/- 54.8 MOmega. The mean antidromic latency from the L1 level was 42.8 +/- 4.4 ms. Axons crossed the midline at the level of the cell body. The activity pattern of the bulbospinal neurones and the L1 root consisted of two bursts per respiratory cycle with a silent period during inspiration. This pattern is characteristic of preinspiratory neurones. We found that 11% of the preinspiratory neurones projected to the area where the bulbospinal neurones were located. These preinspiratory neurones were found in the rostral ventrolateral medulla close (200-350 mum) to the ventral surface at the level of the rostral half of the nucleus retrofacialis. Our data suggest the operation of a disynaptic pathway from the preinspiratory neurones to the L1 motoneurones in the in vitro preparation. We propose that the same pathway is responsible for rhythmic activation of the abdominal muscles during opioid-induced apnoea in the newborn rat.