[Suppression by pancuronium and tubocurarine of the afferent discharge of the muscle spindle induced by succinylcholine].

Effect of pancuronium on the increased afferent discharge of the muscle spindle induced by succinylcholine (SCC) (Succinylcholine induced discharge, SID) was studied in the decerebrate cat by recording the discharge of the muscle nerve going to the gastrocnemius muscle. This action of pancuronium was compared with that of tubocurarine and the antagonistic action if any by neostigmine of this action of pancuronium and tubocurarine was also studied. Pancuronium 0.025 or 0.05mg.kg-1 reduced the peak values of SID to 25.2% and 6.8% of the control value respectively. Tubocurarine 0.125mg.kg-1 reduced this to 38.2%. Inhibition of the SID by pancuronium or tubocurarine was not reversed by the administration of neostigmine. Thus pancuronium reduced SID depending on its dose. The ability of pancuronium and tubocurarine to suppress SID is related to their neuromuscular blocking effects, but the failure by neostigmine to reverse this action of pancuronium or tubocurarine might suggest a different type of reaction at the acetylcholine receptor of the intrafusal fiber compared with the one at the acetylcholine receptor of the skeletal muscle.