STIMULATED SINGLE-FIBER ELECTROMYOGRAPHY IN THE RAT

We constructed an animal model of stimulated single-fiber electromyogr aphy (SFEMG) by testing Wistar rats under anesthesia. Stimuli of 1 Hz were applied to the sciatic nerve through an insulated monopolar needl e electrode. Single-fiber action potentials were acquired from the gas trocnemius muscle. Jitter was assessed by the mean consecutive differe nce (MCD). Eighty-seven fibers were obtained from 12 rats. Their MCDs ranged from 2 to 72 mu s (17.7 +/- 13.4). Seven of these values were l ess than or equal to 5 mu s, and three exceeded 50 mu s. Neuromuscular blocking agents injected into some of the rats induced considerable i ncreases in jitter and blocking. A rat with one fiber with an MCD less than 5 us also received an injection of curare. The jitter showed the same pattern of increment, evidence that the small jitter was not att ributable to direct muscle stimulation. These results show that SFEMG can be used on rats. In addition, jitter reflects the changes in motor end-plate function. The findings also suggest the presence of an extr emely high safety factor in rat neuromuscular junctions. (C) 1998 John Wiley & Sons, Inc.