Abstract
Since the cholinergic theory of neuromuscular transmission depends in part on recovery of ACh after stimulation of motor nerve and since there has been scattered evidence of ACh release by chronically denervated muscle, it seemed important to explore more systematically ACh release by denervated muscle.
By means of the in vitro rat phrenic nervediaphragm technique, comparisons have been made of ACh release by innervated and chronically denervated paired hemidiaphragms, both at rest and during stimulation.
Assays of the bathing fluid showed that in a given time period, the amounts of ACh liberated by innervated and chronically denervated paired hemidiaphragms did not differ, whether the muscles were at rest or were driven by electrical stimuli at rates of 1/sec and 5/sec.
The amounts of ACh liberated were proportional to the degree of activity of the muscles up to a stimulation rate of 5/sec. In a comparable period, resting muscles liberated only 1/7th the amount of ACh released by muscles stimulated at 1/sec.
For both innervated and chronically denervated preparations, the data strongly implicate muscle as the principal tissue of ACh origin, and therefore suggest that in the normal neuromuscular structure, formation and release of ACh may be unrelated to synaptic events.
Footnotes
- Received June 26, 1963.
- Accepted July 30, 1963.
- The Williams & Wilkins Company