A comparative study of the effects of ions on whole nerve and isolated single nerve fiber preparations of crustacean neuromuscular systems

Waterman, Talbot Howe

Jour Cell And Comp Physiol 18(1): 109-126

1941


DOI: 10.1002/jcp.1030180112
Accession: 029620326

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Abstract
The contractile responses of the flexor dactyl muscle to stimulation of the whole leg nerve (in Panulirus, Maia, and Cambarus) and to stimulation of isolated single motor nerve fibers (in Cambarus) have been isometrically recorded. The tension developed in response to brief tetanizing stimulation varied inversely with the amount of Mg in the perfusion fluid, being greatest when none of this ion was present and approaching zero when four to five times the normal amt. was perfused. Changes in perfusion fluid Ca usually gave rather irregular results, but some single nerve fiber expts. suggested that this ion had qualitatively different effects on the slow and the fast neuromuscular systems. Increased K led to decreased contractile responses in whole nerve prepns. and single nerve fiber prspns. of the slow closer system but to markedly increased contractile responses in single nerve fiber prepns. of the fast closer system. Exactly comparable results were found when both the slow and the fast closer motor fibers were prepared and alternately stimulated in the same nerve muscle prep. Evidence is cited suggesting that these K effects occurred at the myoneural junction in some of the steps involved in neuromuscular transmission.

A comparative study of the effects of ions on whole nerve and isolated single nerve fiber preparations of crustacean neuromuscular systems