In vivo visualization of the growth of pre- and postsynaptic elements of neuromuscular junctions in the mouse.

@article{citeulike:2943436, abstract = {In order to study how neuromuscular junctions grow, we have repeatedly viewed the same junctions in mouse sternomastoid muscles at monthly intervals from 2 weeks to 18 months of age. Motor nerve terminals were stained with the nontoxic fluorescent dye 4-Di-2-ASP (Magrassi et al., 1987), and postsynaptic ACh receptors were labeled with fluorescently tagged alpha-bungarotoxin. Neuromuscular junctions grew primarily by expansion of existing motor nerve terminal and postsynaptic receptor regions without the addition or loss of synaptic areas. The expansion of pre- and postsynaptic specializations was precisely matched, suggesting that as neuromuscular junctions grow, the opposing specializations enlarge simultaneously. Each neuromuscular junction grew in length and width at the same rate that muscle fibers enlarged in those 2 dimensions, suggesting that junctional growth might be a mechanical consequence of muscle fiber growth. Repeated visualization of ACh receptors over time showed that previously labeled receptors spread apart in the membrane occupying a progressively larger area as muscle fibers grew. At the same time, new receptors were intercalated throughout the enlarged postsynaptic area. Thus, the growth of postsynaptic regions appears to be directly related to the expansion of the muscle fiber membrane as muscle fibers grow. The maintained alignment between growing motor nerve terminals and postsynaptic regions suggests that nerve terminal growth may be a consequence of its adhesion to growing postsynaptic specializations. This conclusion is supported by the coextensive stretching of motor nerve terminals and postsynaptic regions when muscle fibers are stretched. Thus, the growth of motor nerve terminals is coupled to the growth of postsynaptic regions, and the growth of the postsynaptic regions is in turn coupled to the growth of muscle fibers. In this way, the branching pattern of neuromuscular junctions may be stably maintained despite ongoing enlargement of synaptic area.}, address = {Department of Anatomy and Neurobiology, Washington University School of Medicine, St. Louis, Missouri 63110.}, author = {Balice-Gordon, R. J. and Lichtman, J. W. }, citeulike-article-id = {2943436}, comment = {There exists 'size-matching': synapses on large muscle fibres release more neurotransmitter than junctions on small fibres. physical size of NMJ correlates both with amount of transmitter released and with the size of the fibre. (Use to look at size strength question?) Using sternomastoid muscle. 2wks-4months = rapid growth in 70\% of (pre)terminals no new branches over 5 months (though only looking at synapse, not at pre-terminal nerve). 33\% gained an addition at some point but they were small and usually just one. 3\% lost a site, also small and 1-2 per junction. When synapses grow almost every branch elongates by intercalary addition. Nerve terminal growth occurs in parallel with an overall expansion of the area. However: The angle of bifurcation changed over time And: initially continuous branches became discontinuous spots. The dye stains mitochondria so maybe distribution is different (or maybe this represents addition of pre-terminal branches in the same location?) In old animals there is also spotty staining but also addition and elimination of branches. Postsynaptic receptors also enlarged by expansion. 3/99 there was addition and 1/99 there was elimination. Pre- and post-synaptic portions were always matched -> grew at the same time (within resolution of technique) New Ach receptors were inserted uniformly intercalarily pre- and post-synaptic elements are adherent because when you stretch the muscle they stretch to the same degree. They believe that pre-synaptic growth does not happen before post-synaptic growth. They argue against the 'replacement hypothesis' that nerve terminals are in a state of continual renewal through sprouting and regeneration.}, issn = {0270-6474}, journal = {The Journal of neuroscience : the official journal of the Society for Neuroscience}, month = {March}, number = {3}, pages = {894--908}, posted-at = {2008-06-30 15:45:31}, priority = {0}, title = {In vivo visualization of the growth of pre- and postsynaptic elements of neuromuscular junctions in the mouse.}, url = {http://view.ncbi.nlm.nih.gov/pubmed/2156964}, volume = {10}, year = {1990} }

TY - JOUR ID - citeulike:2943436 L3 - citeulike-article-id:2943436 N2 - In order to study how neuromuscular junctions grow, we have repeatedly viewed the same junctions in mouse sternomastoid muscles at monthly intervals from 2 weeks to 18 months of age. Motor nerve terminals were stained with the nontoxic fluorescent dye 4-Di-2-ASP (Magrassi et al., 1987), and postsynaptic ACh receptors were labeled with fluorescently tagged alpha-bungarotoxin. Neuromuscular junctions grew primarily by expansion of existing motor nerve terminal and postsynaptic receptor regions without the addition or loss of synaptic areas. The expansion of pre- and postsynaptic specializations was precisely matched, suggesting that as neuromuscular junctions grow, the opposing specializations enlarge simultaneously. Each neuromuscular junction grew in length and width at the same rate that muscle fibers enlarged in those 2 dimensions, suggesting that junctional growth might be a mechanical consequence of muscle fiber growth. Repeated visualization of ACh receptors over time showed that previously labeled receptors spread apart in the membrane occupying a progressively larger area as muscle fibers grew. At the same time, new receptors were intercalated throughout the enlarged postsynaptic area. Thus, the growth of postsynaptic regions appears to be directly related to the expansion of the muscle fiber membrane as muscle fibers grow. The maintained alignment between growing motor nerve terminals and postsynaptic regions suggests that nerve terminal growth may be a consequence of its adhesion to growing postsynaptic specializations. This conclusion is supported by the coextensive stretching of motor nerve terminals and postsynaptic regions when muscle fibers are stretched. Thus, the growth of motor nerve terminals is coupled to the growth of postsynaptic regions, and the growth of the postsynaptic regions is in turn coupled to the growth of muscle fibers. In this way, the branching pattern of neuromuscular junctions may be stably maintained despite ongoing enlargement of synaptic area. IS - 3 JF - The Journal of neuroscience : the official journal of the Society for Neuroscience SN - 0270-6474 AD - Department of Anatomy and Neurobiology, Washington University School of Medicine, St. Louis, Missouri 63110. EP - 908 TI - In vivo visualization of the growth of pre- and postsynaptic elements of neuromuscular junctions in the mouse. VL - 10 SP - 894 N1 - There exists 'size-matching': synapses on large muscle fibres release more neurotransmitter than junctions on small fibres. physical size of NMJ correlates both with amount of transmitter released and with the size of the fibre. (Use to look at size strength question?) Using sternomastoid muscle. 2wks-4months = rapid growth in 70% of (pre)terminals no new branches over 5 months (though only looking at synapse, not at pre-terminal nerve). 33% gained an addition at some point but they were small and usually just one. 3% lost a site, also small and 1-2 per junction. When synapses grow almost every branch elongates by intercalary addition. Nerve terminal growth occurs in parallel with an overall expansion of the area. However: The angle of bifurcation changed over time And: initially continuous branches became discontinuous spots. The dye stains mitochondria so maybe distribution is different (or maybe this represents addition of pre-terminal branches in the same location?) In old animals there is also spotty staining but also addition and elimination of branches. Postsynaptic receptors also enlarged by expansion. 3/99 there was addition and 1/99 there was elimination. Pre- and post-synaptic portions were always matched -> grew at the same time (within resolution of technique) New Ach receptors were inserted uniformly intercalarily pre- and post-synaptic elements are adherent because when you stretch the muscle they stretch to the same degree. They believe that pre-synaptic growth does not happen before post-synaptic growth. They argue against the 'replacement hypothesis' that nerve terminals are in a state of continual renewal through sprouting and regeneration. AU - Balice-Gordon, RJ AU - Lichtman, JW PY - 1990/03// UR - http://view.ncbi.nlm.nih.gov/pubmed/2156964 ER -