PENICILLAMINE-INDUCED MYASTHENIC RESPONSES IN THE GUINEA-PIG

To study the basis for the myasthenic illness that develops in some patients receiving D‐penicillamine (D‐P), we measured neuromuscular transmission in D‐P‐treated guinea pigs. Treated animals manifested edrophonium chloride–repairable decremental responses to 30‐Hz nerve stimulation (8.5% ± 1.5%—mean ± SEM; N = 16) compared with the response in saline‐treated control animals (−0.3% ± 0.85%, N = 10, p <0.005). Posttetanic phenomena were studied in 5 treated animals; 3 revealed posttetanic exhaustion. Miniature endplate potential (MEPP) amplitudes were significantly reduced in 11 treated animals (0.612 ± 0.016 mV) compared with 6 controls (0.713 ± 0.024 mV, p <0.01). The MEPP frequency appeared reduced in treated animals. Both MEPP amplitude and MEPP frequency correlated with the decrement. Copyright © 1979 Houghton Mifflin Professional Publishers