title: Extrasynaptic accumulations of acetylcholinesterase in the rat sternocleidomastoid muscle after neonatal denervation. Light and electron microscopic localization and molecular forms.
abstract: Denervated neonatal rat sternocleidomastoid muscle has decreased levels of total AChE when compared to control muscle. Denervated versus control values of total muscle AChE present a three-phase curve in function of time after denervation. There is a rapid initial fall 0-3 days after denervation, an increase during about 2 weeks, then again a decrease in total AChE. Thus, there is a transitory net accumulation of AChE after the initial fall of activity in denervated developing muscle. Extrasynaptic areas of high AChE activity develop between 1 and 2 weeks after denervation and remain visible up to 1 month after denervation before vanishing. An electron microscope study shows that these accumulations are internal to the muscle fiber, close to a limited number of muscle nuclei and associated to the sarcoplasmic reticulum and nuclear envelope, but not to the T-tubule system. As found in adult rat muscle, the initial fall in AChE affects first the 16 S AChE form, and soon after, the 4 S and 10 S AChE forms. A main difference with adult muscle is the sudden increase and predominance over other forms of 10 S AChE 2 weeks after denervation at birth. Later, the decrease in AChE affects 16 S and 4 S AChE before 10 S AChE. The regions rich in extrasynaptic sites of AChE accumulation possess a very high proportion of 10 S AChE. Thus, the mechanisms of biosynthesis, intracellular transport and/or secretion of AChE may be very different in young, developing muscle compared to adult muscle.
mesh_terms: D000110:Acetylcholinesterase / Q000378:metabolism*; D000818:Animals; D000831:Animals, Newborn; D002499:Centrifugation, Density Gradient; D009121:Muscle Denervation; D009124:Muscle Proteins / Q000032:analysis; D009132:Muscles / Q000201:enzymology* / Q000294:innervation / Q000648:ultrastructure; D009685:Nuclear Envelope / Q000201:enzymology; D051381:Rats; D011919:Rats, Inbred Strains; D012519:Sarcoplasmic Reticulum / Q000201:enzymology
chemical_list: D009124:Muscle Proteins; D000110:Acetylcholinesterase