Density of AChoRs [acetylcholine receptors]

Range at embryonic day 16 of gestation 2,000-3,000: at birth ~9,000 sites/µm^2
Organism Mouse Mus musculus
Reference Matthews-Bellinger JA, Salpeter MM. Fine structural distribution of acetylcholine receptors at developing mouse neuromuscular junctions. J Neurosci. 1983 Mar3(3):644-57. abstractPubMed ID6827314
Method "The distribution of acetylcholine receptors (AChRs) in neuromuscular junctions of embryonic and newborn mice (strain 129/ReJ) was examined on the fine structural level using [125I]a-bungarotoxin labeling and quantitative electron microscope autoradiography. Changes in junctional receptor site density were related to changes in the structure of the postjunctional membrane, in particular the differentiation of morphologically distinct regions of thickened membrane and the formation of junctional folds."
Comments "The following sequence of development is described: (1) At the earliest age examined, embryonic day 16 of gestation (i.e., at approximately the time when junctional receptor accumulations are first detected), subneural receptor aggregates have poorly defined boundaries and seem to extend beyond the region of direct axonal or Schwann cell contact. At that time the subneural AChR site density is somewhat variable but averages ~2000 to 3000sites/µm^2, and the subneural muscle membrane shows discontinuous membrane specialization (membrane thickening plus a cytoplasmic amorphous layer). There seems to be no preferential labeling of contact regions rich in such specialization compared with those where membrane thickening was less obvious or absent. (2) By birth, junctional AChRs are strongly correlated with morphologically specialized membrane, at a constant density of approximately 9000sites/µm^2 (comparable to that in adult animals of this strain of mouse)."
Entered by Uri M
ID 111079