Effects of calcium channel blocking agents on neostigmine-induced fasciculations.
Male Sprague-Dawley rats were anesthetized with pentobarbital and prepared for monitoring contractions of the gastrocnemius muscle evoked by stimulation of the sciatic nerve. Animals received atropine prior to a dose of neostigmine of 0.02 mg/kg i.v. The effects on contractile strength and the number of fasciculations in a 2-min period were assessed. Pretreatment with phenytoin, 20 mg/kg, reduced the number of fasciculations to 32% of control without altering contractile strength. Both nifedipine and nitrendipine, 1 mg/kg each, virtually abolished fasciculations without altering twitch strength. Verapamil, 4 and 8 mg/kg, depressed fasciculation frequency to 50% of control without affecting pre-neostigmine twitch height. The dihydropyridine calcium blocking agents did however reduce the neostigmine-induced augmentation of contraction strength. These data suggest that a calcium-mediated current at presynaptic motor endings participates in the generation of repetitive nerve terminal discharges leading to muscle fasciculations.
Raines
A
A
Department of Pharmacology, Georgetown University School of Medicine, Washington, D.C. 20007.
Henderson
T R
TR
Dretchen
K L
KL
D000818:Animals; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D004558:Electric Stimulation; D005152:Facial Muscles / Q000187:drug effects / Q000502:physiology; D005207:Fasciculation / Q000139:chemically induced / Q000517:prevention & control*; D008297:Male; D009388:Neostigmine / Q000037:antagonists & inhibitors*; D009411:Nerve Endings / Q000187:drug effects; D009543:Nifedipine / Q000494:pharmacology; D009568:Nitrendipine / Q000494:pharmacology; D010672:Phenytoin / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D014700:Verapamil / Q000494:pharmacology
D002121:Calcium Channel Blockers; D009388:Neostigmine; D010672:Phenytoin; D009568:Nitrendipine; D014700:Verapamil; D009543:Nifedipine