Donahue S P, English A W
Department of Anatomy and Cell Biology, Emory University School of Medicine, Atlanta, Georgia 30322.
Dev Biol. 1987 Dec;124(2):481-9. doi: 10.1016/0012-1606(87)90501-x.
To investigate the specificity of development of initial neuromuscular connections, we examined the compartmental distribution of synapses in neonatal rat lateral gastrocnemius (LG) muscle. Initial neuromuscular connections might be restricted to the compartmental territories present in adults; alternatively, synapse elimination could establish the compartments from a less precise pattern of innervation. We examined 46 pups of ages 0 to 14 postnatal days using a variety of techniques. The principle method was evoked electromyographic (EMG) activity in response to nerve stimulation. The nerve branch to one neuromuscular compartment was cut and the remainder of the nerve was stimulated. The presence of EMG activity was used to identify the areas of muscle contracting in response to nerve stimulation. After cutting a particular branch, EMG activity generally could not be recorded from the denervated compartment. These results indicate that the pattern of innervation at birth is essentially compartment-specific, and that neuromuscular compartments are not shaped from some less precise pattern by postnatal synapse elimination. The factors which operate prenatally to determine this high degree of specificity in neuromuscular connectivity seen at the time of birth, however, remain unknown.
为了研究初始神经肌肉连接发育的特异性，我们检查了新生大鼠外侧腓肠肌（LG）中突触的分区分布。初始神经肌肉连接可能局限于成体中存在的分区区域；或者，突触消除可能从不太精确的神经支配模式建立这些分区。我们使用多种技术检查了46只出生后0至14天的幼崽。主要方法是记录对神经刺激作出反应的诱发肌电图（EMG）活动。切断支配一个神经肌肉分区的神经分支，然后刺激其余的神经。通过EMG活动的存在来识别肌肉中对神经刺激作出反应而收缩的区域。切断特定分支后，通常无法从去神经支配的分区记录到EMG活动。这些结果表明，出生时的神经支配模式本质上是分区特异性的，并且神经肌肉分区并非由出生后的突触消除从某种不太精确的模式形成。然而，产前决定出生时所见神经肌肉连接高度特异性的因素仍然未知。
