Some Factors Influencing Production of Ulcers in the Shay Rat

Abstract

FACTORS INFLUENCINGport inferred that muscle fasciculations result from a direct action of the blood on the muscle fibers, Under the condi tilons of these experiments, it is evident that the fasciculations and tonic spasms occasioned by alkalosis and hypocalcemia can occur as the result of spontaneous iterative discharges arising in peripheral motor nerve fibers or their terminations in the motor end plates. These results cannot, of course, preclude the possibility of the participation of neurons within the central nervous system, or of sensory neurons in spinal and perhaps even supraspinal reflex arcs. In fact, there is considerable evidence that sensory fibers also are irritated and discharge repetitively in human tetany ( 2 ) . However, our results strongly suggest that activation of peripheral motor nerve fibers or terminations account for the motor manifestations of tetany whether caused by an elevation in blood pH or a reduction in ionized blood calcium. This view is supported by Kugelberg's( 15) finding in one human subject with inveterate hypocalcemic tetany that impulses occurring in the fourth interosseous muscle of the hand and recorded electromyographically continued unaltered after apparently effective procaine block of the ulnar nerve at the elbow.Sumnaar.v. 1. Tetany was produced acutely in eleven cats and one dog with solutions of sodium bicarbonate, sodium carbonate and a phosphate buffer administered by venoclysis. Fasciculations and tonic spasms involving especially the head and forelimb musculature characterized this form of tetany. Clonic spasiiis were were not seen in anesthetized ani-SHAY RAT VLCERATION 333 mals. 2. Section of the hypoglossal nerve did not significantly influence the fasciculations oi the tongue musculature. Section oi the brachial plexus did not significantly inhence the fasciculations or tonic spasms of the iorelimb musculature. 3. Paralvtic doses of dtubocurarine blocked all motor maniiestations of tetany. 4. It was concluded that all of the motor phenomena characterizing alkalotic and hypocalcemic tetany could result from the spontaneous iterative discharges occurring in peripheral motor nerye fibers or their terminations.In our experience, the incidence of ulcers paper. Recently, Madden ef QZ. ( 1) in a critiin the Shay rat varied from 100% to 25%. cal study of the Shay procedure concluded There are no apparent reasons for this varia-that the method is valuable for the study oi tion, and some of the complicating, but sig-gastric secretion and of less value ior the study nificant, observations are recorded in this of the ulceration mechanism. We have used