Mazza E, Núñez-Abades P A, Spielmann J M, Cameron W E
Department of Behavioral Neuroscience, University of Pittsburgh, PA 15260.
Brain Res. 1992 Dec 11;598(1-2):127-37. doi: 10.1016/0006-8993(92)90176-a.
Dye-, tracer- and electrotonic coupling were studied independently in genioglossal (GG) motoneurons using intracellular recordings in in vitro brainstem slices from rats postnatal ages 1-30 days. The subpopulation of GG motoneurons were retrogradely labeled after an injection of dextran-rhodamine into the posterior tongue. Dye-coupling was studied with Lucifer yellow injected into 55 motoneurons and tracer-coupling with neurobiotin injected into 89 presumptive GG motoneurons. Of the motoneurons injected with Lucifer yellow, only 6 of 41 cells (16.2%) exhibited dye-coupling; all occurred in animals less than 9 days old. In all but one instance, dye-coupling was restricted to only one other cell. No evidence of dye-coupling was found in the 14 cells injected in animals older than 8 days. Tracer-coupling (neurobiotin) was demonstrated in 12 of 30 cells (40%) from animals 1-2 days old and in 6 of 21 cells (28.6%) from animals 3-8 days old. Of the remaining 38 cells from animals 10 days of age and older, only one cell was found to be tracer-coupled. Cells injected with neurobiotin were coupled to an average of two other cells. Electrotonic coupling, as demonstrated with a short latency depolarization (SLD) in response to stimulation of hypoglossal axons, was found in developing GG motoneurons. These SLDs were revealed in 17 of 40 GG motoneurons (42.5%) examined in 1-8-day-old animals. There were no SLDs recorded in the 10 cells examined from animals of 10 days and older. The significance of coupling relative to patency of the newborn upper airways is discussed.
利用细胞内记录技术，在出生后1 - 30天大鼠的体外脑干切片中，对颏舌肌（GG）运动神经元的染料耦合、示踪剂耦合和电紧张耦合进行了独立研究。在向舌后部注射葡聚糖罗丹明后，对GG运动神经元亚群进行逆行标记。向55个运动神经元注射鲁米诺黄来研究染料耦合，向89个假定的GG运动神经元注射神经生物素研究示踪剂耦合。在注射鲁米诺黄的运动神经元中，41个细胞中只有6个（16.2%）表现出染料耦合；均发生在9日龄以下的动物中。除一例之外，染料耦合仅限于另一个细胞。在8日龄以上动物注射的14个细胞中未发现染料耦合的证据。在1 - 2日龄动物的30个细胞中有12个（40%）以及3 - 8日龄动物的21个细胞中有6个（28.6%）显示出示踪剂耦合（神经生物素）。在10日龄及以上动物的其余38个细胞中，仅发现一个细胞有示踪剂耦合。注射神经生物素的细胞平均与另外两个细胞耦合。通过对舌下神经轴突刺激产生的短潜伏期去极化（SLD）证明，发育中的GG运动神经元存在电紧张耦合。在1 - 8日龄动物检查的40个GG运动神经元中有17个（42.5%）出现了这些SLD。在10日龄及以上动物检查的10个细胞中未记录到SLD。讨论了耦合相对于新生儿上呼吸道通畅的意义。
