In vitro denervation of frog skeletal muscle: expression of several conductance classes of nicotinic receptors.
The question arose as to whether the altered kinetic properties of the nicotinic acetylcholine receptor-ion channel complex (AChR) observed after muscle denervation could be due to post-translational modifications. Single AChR properties of in vitro denervated skeletal muscle were studied using the cell-attached patch-clamp technique. Patch-clamp recordings from junctional regions of fibers daily treated with cycloheximide, a protein synthesis inhibitor, and phenylmethylsulfonyl fluoride, a protease inhibitor, revealed single conductance class of acetylcholine (ACh)-activated currents after acute dissociation and several conductance classes 3-14 days after muscle denervation. alpha-Bungarotoxin blocked all conductance states induced by ACh. Biochemical assays carried out on the same experimental conditions disclosed that chronic treatment of the fibers with cycloheximide inhibited the incorporation of [3H]leucine into precipitable protein. The present findings provided evidence that the altered functional properties of nicotinic receptors after muscle denervation may occur without new transcription.
Rozental
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Institute of Biophysics Carlos Chagas Filho, Federal University of Rio de Janeiro, Ilha do Fundão, Brazil.
D000109:Acetylcholine / Q000502:physiology; D000818:Animals; D002038:Bungarotoxins / Q000494:pharmacology; D003513:Cycloheximide / Q000494:pharmacology; D003655:Decerebrate State; D066298:In Vitro Techniques; D007473:Ion Channels / Q000187:drug effects / Q000502:physiology; D009045:Motor Endplate / Q000187:drug effects / Q000502:physiology; D009121:Muscle Denervation; D009431:Neural Conduction / Q000187:drug effects / Q000502:physiology*; D011894:Rana pipiens; D011978:Receptors, Nicotinic / Q000187:drug effects / Q000502:physiology*
D002038:Bungarotoxins; D007473:Ion Channels; D011978:Receptors, Nicotinic; D003513:Cycloheximide; D000109:Acetylcholine