Time dependence of Li+ action on acetylcholinesterase activity in correlation with spontaneous quantal release of acetylcholine in rat diaphragm.
The mean miniature end-plate potential (m.e.p.p.) frequency and the acetylcholinesterase (AChE) activity have been examined in the rat diaphragm, in relation to the time of Li+ action. Substitution of LiCl for NaCl caused increase in m.e.p.p. frequency, the final level of which depended on Li+ concentration in the bath solution. Incubation of diaphragm homogenate with NaCl caused initially a slight increase of AChE activity, reaching a plateau after 20 min. Substitution of LiCl for NaCl produced an increase in AChE activity to a maximum, followed by a decrease to a minimum. The activity consequently returned to a steady level. During complete substitution of LiCl for NaCl, the maximum value of AChE activity coincided with the maximum m.e.p.p. frequency (Fmax) induced by Li+; the minimum value correlated with the precise instant that the frequency reached a plateau. The addition of prostigmine caused: a) blockade of AChE activity, and b) prostigmine concentration-dependent decrease of Fmax and/or disappearance of m.e.p.p.s from neuromuscular junctions treated with Li+. These results are discussed in terms of correlation between changes of AChE activity induced by Li+ and variations of spontaneous quantal release of the transmitter from nerve terminals of the rat diaphragm treated with Li+.
Kouniniotou-Krontiri
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P
Department of Experimental Physiology, University of Athens, Medical School, Greece.
Tsakiris
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S
D000110:Acetylcholinesterase / Q000378:metabolism*; D000818:Animals; D002712:Chlorides / Q000494:pharmacology; D003964:Diaphragm; D008094:Lithium / Q000494:pharmacology*; D018021:Lithium Chloride; D008564:Membrane Potentials; D009132:Muscles / Q000201:enzymology*; D009388:Neostigmine / Q000494:pharmacology; D051381:Rats; D012965:Sodium Chloride / Q000494:pharmacology; D013997:Time Factors
D002712:Chlorides; D009388:Neostigmine; D012965:Sodium Chloride; D008094:Lithium; D000110:Acetylcholinesterase; D018021:Lithium Chloride