TY - JOUR
T1 - Nonjunctional acetylcholine receptor channel open time decreases during development of Xenopus muscle
AU - Kullberg, R. W.
AU - Brehm, P.
AU - Steinbach, J. H.
PY - 1981
Y1 - 1981
N2 - The mean channel open time of junctional acetylcholine receptors (AChRs) decreases during development of mammalian skeletal neuromuscular junctions 1-3. The junctional AChRs of newborn rats have long mean channel open times of about 4.5 ms and in this respect are similar to nonjunctional AChRs of adult denervated muscle3-5. Mature neuromuscular junctions have channels with shorter mean open times of about 1 ms, whereas junctions at intermediate stages seem to have a mixture of channels with short and long open times1-3. These observations, taken together with findings on receptor distribution during development6,14, suggest that the establishment of nerve-muscle contact induces an aggregation of embryonic AChRs with long mean channel open times at the point of contact and that these embryonic junctional receptors are then replaced, modified or subjected to local membrane changes leading to a discrete reduction in channel open time. However, the fate of those embryonic nonjunctional receptors which are not aggregated at the newly formed neuromuscular junction is unknown. Are they an unchanging population, or do the changes in kinetic behaviour which occur at the junctional regions also take place at other regions of the muscle membrane? The kinetics of nonjunctional receptors in mammalian skeletal muscle have not been studied during development. We have now, however, examined this question in amphibian myotomal muscle, where nonjunctional receptors are present in substantial numbers throughout development, making it possible to measure the mean open time of both classes of AChR channel. We observed a shortening of mean channel open time of junctional AChRs, from about 3 ms to 1 ms, and an identical change in mean channel open time of AChRs at nonjunctional regions of membrane.
AB - The mean channel open time of junctional acetylcholine receptors (AChRs) decreases during development of mammalian skeletal neuromuscular junctions 1-3. The junctional AChRs of newborn rats have long mean channel open times of about 4.5 ms and in this respect are similar to nonjunctional AChRs of adult denervated muscle3-5. Mature neuromuscular junctions have channels with shorter mean open times of about 1 ms, whereas junctions at intermediate stages seem to have a mixture of channels with short and long open times1-3. These observations, taken together with findings on receptor distribution during development6,14, suggest that the establishment of nerve-muscle contact induces an aggregation of embryonic AChRs with long mean channel open times at the point of contact and that these embryonic junctional receptors are then replaced, modified or subjected to local membrane changes leading to a discrete reduction in channel open time. However, the fate of those embryonic nonjunctional receptors which are not aggregated at the newly formed neuromuscular junction is unknown. Are they an unchanging population, or do the changes in kinetic behaviour which occur at the junctional regions also take place at other regions of the muscle membrane? The kinetics of nonjunctional receptors in mammalian skeletal muscle have not been studied during development. We have now, however, examined this question in amphibian myotomal muscle, where nonjunctional receptors are present in substantial numbers throughout development, making it possible to measure the mean open time of both classes of AChR channel. We observed a shortening of mean channel open time of junctional AChRs, from about 3 ms to 1 ms, and an identical change in mean channel open time of AChRs at nonjunctional regions of membrane.
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U2 - 10.1038/289411a0
DO - 10.1038/289411a0
M3 - Article
C2 - 6258078
AN - SCOPUS:0019465297
SN - 0028-0836
VL - 289
SP - 411
EP - 413
JO - Nature
JF - Nature
IS - 5796
ER -