The Effect of Catecholamines on the Influx of Calcium and the Development of Tension in Denervated Mouse Diaphragm Muscle

Abstract

The nature of the catecholamine‐induced contracture of chronically denervated mouse diaphragm muscle has been investigated and compared with the contractural response evoked by acetylcholine. The time course of onset of catecholamine‐sensitivity in denervated diaphragm muscles was similar to the development of acetylcholine sensitivity. However, catecholamine contractures were absent in tissues denervated for periods longer than 90 days whereas acetylcholine‐sensitivity was still evident several months after denervation. The catecholamine‐induced contracture of the denervated muscle was inhibited specifically by β‐receptor blocking drugs and was unaffected by α‐receptor blocking drugs and cholinoceptor antagonists. Catecholamine‐induced contractures of denervated muscles, unlike contractures to acetylcholine, were dependent upon the presence of spontaneous fibrillation and the amplitude of spontaneous fibrillation was increased by catecholamines. Fibrillation was absent in the presence of tetrodotoxin (1 μm), 2,4‐dinitrophenol (10 μm), potassium cyanide (10 μm), ouabain (100 μm), in lithium chloride Ringer solution and at low temperature. Under these conditions catecholamine‐induced contractures, but not those to acetylcholine, were abolished. Labelled calcium was found progressively to enter denervated muscle fibres and this entry of calcium was increased by catecholamines. It is suggested that this calcium entry may represent either an increased calcium permeability of denervated muscle fibres which is increased further by catecholamines or the presence of a calcium current that occurs during the fibrillatory potentials of denervated muscle.

The effects of β‐adrenoceptor activation on contraction in isolated fast‐ and slow‐twitch skeletal muscle fibres of the rat

“…Changes in resting force were also observed in denervated fibres. Catecholamines induce contractures in denervated muscle (Bowman & Raper, 1965;Evans & Smith, 1976) and adrenaline induced contractures with increased fibrillations in this study. In contrast, terbutaline and dbcyclic AMP reduced resting force and depressed fibrillations (Figure 9).…”

“…Skeletal muscle is thought to become supersensitive to catecholamines following chronic denervation as catecholamine-induced contractures have been reported (Bowman & Raper, 1965;Evans & Smith, 1976). It was possible that the denervated muscles may also become supersensitive to terbutaline.…”

Cellular uptake of L-lactate in mouse diaphragm

“…We estimated the extracellular space as 0.277 ml/g. Evans and Smith (1976) found a value of 0.28 ml/g for mouse diaphragm. The tortuosity factor that we estimated is higher than those that have been estimated for rat diaphragm.…”

Intrinsic neuromuscular defects in the neurogenic bladder: V. Autonomic re‐innervation of the male feline rhabdosphincter following somatic denervation by bilateral sacral ventral rhizotomy

“…Supersensitivity to acetylcholine is associated with "expansion" of nicotinic cholinergic receptor sites along the entire length of the myofiber, beyond their normal localization at and in the immediate vicinity of the original motor endplates [Axelsson and Thesleff, 1959;Miledi, 1960a;Guth, 1968;McArdle and Albuquerque, 1973;Harris, 19741. Catecholamine supersensitivity of the myofiber is manifested in vivo and/or in vitro by increase in its spontaneous electrical activity, the frequency of its fibrillation potential and/or tone, with true myofiber contracture [Euler and Gaddum, 1983;Bulbring and Burn, 1936;Montagu, 1955, Bhoola andSchachter, 1961;Bowman and Zaimis, 1961;Paterson, 1963;Bowman and Raper, 1965;Raper and Bowman, 1968;Turkanis, 1969;Luco and Sinchez, 1956;Luco and Luco, 1971;Bhoola et al, 1972;Yamada, 1974;Yamada and Harigaya, 1974;Evans and Smith, 1976;Smith and Thesleff, 19761. The adrenoceptors involved in these reponses have been identified as beta Raper, 1965, 1967;Banerjee et al, 1977;Rodger and Bowman, 19831, alpha [Eakins and Katz, 19671, or both beta and alpha [Paterson, 1963;Yamada and Harigaya, 19741, probably depending on the species studied.…”