Summary
The effects of reduced muscle activity on the ultra structural development of the rat neuromuscular junction (NMJ) have been studied. Soleus muscles of rats were treated with α-bungarotoxin (αBTx) in order to produce a postsynaptic block of activity between the ages of 10 and 12 days. Muscles of litter mates were treated with saline over the same period. The development of these control and αBTx treated muscles was then compared to that of normal muscles from untreated litter mates. During the period between the tenth and twelfth days after birth, normal soleus NMJs show two major ultrastructural changes. 1. The average number of axon terminal profiles present at each endplate decreases. This is thought to reflect the withdrawal of superfluous axons from the endplates. 2. There is an increasing specialization of the postsynaptic structures of the junction: complexity of folding of the muscle junctional membrane increases, as does the accumulation of subjunctional sarcoplasm and muscle nuclei.
In soleus muscles treated with αBTx, the number of axon terminal profiles observed at the endplates does not decrease, suggesting that elimination of supernumerary axons does not occur. In addition, specialization of the postsynaptic structures of the NMJ is retarded during the period of ACh receptor block.
Similar content being viewed by others
References
Bennett, M. R. &Pettigrew, A. G. (1974) The formation of synapses in striated muscle during development.Journal of Physiology 241, 515–45.
Brown, M. C., Holland, R. L. &Hopkins, W. G. (1980) Some effects of botulinum toxin on the motor innervation of neonatal rat muscles.Journal of Physiology 307, 17P.
Brown, M. C., Holland, R. L. &Hopkins, W. G. (1981) Restoration of focal multiple innervation in rat muscles by transmission block during a critical stage of development.Journal of Physiology 318, 355–64.
Brown, M. C., Jansen, J. K. S. &Van Essen, D. (1976) Polyneuronal innervation of skeletal muscle in new-born rats and its elimination during maturation.Journal of Physiology 261, 387–422.
Duxson, M. J. &Stolkin, C. (1979) Early structural changes in the motor nerve terminals of rat skeletal muscle after local injection of botulinum toxin.Journal of Physiology 296, 12P.
Gordon, T., Jones, R. &Vrbová, G. (1976) Changes in chemosensitivity of skeletal muscles as related to endplate formation.Progress in Neurobiology 6, 103–36.
Gordon, T., Perry, R., Tuffery, A. R. &Vrbová, G. (1974) Possible mechanisms determining synapse formation in developing skeletal muscles of the chick.Cell and Tissue Research 155, 13–25.
Harris-Flanagan, A. H. (1969) Differentiation and degeneration in the motor horn of the foetal mouse.Journal of Morphology 129, 281–306.
Katz, B. &Miledi, R. (1967) Tetrodotoxin and neuromuscular transmission.Proceedings of the Royal Society of London, Series B 167, 8–22.
Korneliussen, H. &Jansen, J. K. S. (1976) Morphological aspects of the elimination of polyneuronal innervation of skeletal muscle fibres in new-born rats.Journal of Neurocytology 5, 591–604.
Miyata, Y. &Yoshioka, K. (1980) Selective elimination of motor nerve terminals in the rat soleus muscle during development.Journal of Physiology 309, 631–46.
O'Brien, R. A. D., Östberg, A. J. C. &Vrbová, G. (1978) Observations on the elimination of polyneural innervation in developing mammalian skeletal muscle.Journal of Physiology 282, 571–82.
Pittman, R. H. &Oppenheim, R. W. (1978) Neuromuscular blockade increases motoneuron survival during normal cell death in the chick embryo.Nature 271, 364–6.
Polak, R. L., Sellin, L. C. &Thesleff, S. (1981) Acetylcholine content and release in denervated or botulinum poisoned rat skeletal muscle.Journal of Physiology 319, 253–60.
Redfern, P. A. (1970) Neuromuscular transmission in new-born rats.Journal of Physiology 209, 701–9.
Riley, D. A. (1977) Spontaneous elimination of nerve terminals from the endplates of developing skeletal myofibers.Brain Research 134, 279–85.
Romanes, G. J. (1946) Motor localization and the effects of nerve injury on the ventral horn cells of the spinal cord.Journal of Anatomy 80, 117.
Sohal, G. S. (1981) Ultrastructural observations on the establishment of neuromuscular junctions following prevention of embryonic death of motoneurons.Experimental Neurology 71, 625–34.
Srihari, T. &Vrbová, G. (1978) The role of muscle activity in the differentiation of neuromuscular junctions in slow and fast chick muscles.Journal of Neurocytology 7, 529–40.
Srihari, T. &Vrbová, G. (1980) Effects of neuromuscular blocking agents on the differentiation of nerve-muscle connections in slow and fast chick muscles.Development, Growth & Differentiation 22, 645–57.
Steinbach, J. H. (1981) Developmental changes in acetylcholine receptor aggregates at rat skeletal neuromuscular junctions.Developmental Biology 84, 267–76.
Thompson, W., Kuffler, D. P. &Jansen, J. K. S. (1979) The effect of prolonged, reversible block of nerve impulses on the elimination of polyneuronal innervation of new-born rat skeletal muscle fibers.Neuroscience 4, 271–81.
Zelená, J. (1962) The effect of denervation on muscle development. InThe Denervated Muscle (edited byGutmann, E.), pp. 103–26. Prague: Publishing House of the Czechoslovak Academy of Sciences.
Zelená, J., Vyskocil, F. &Jirmanová, I. (1979) The elimination of polyneuronal innervation of endplates in developing rat muscles with altered function.Progress in Brain Research 49, 365–72.
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Duxson, M.J. The effect of postsynaptic block on development of the neuromuscular junction in postnatal rats. J Neurocytol 11, 395–408 (1982). https://doi.org/10.1007/BF01257985
Received:
Revised:
Accepted:
Issue Date:
DOI: https://doi.org/10.1007/BF01257985