Prejunctional effects of vecuronium in the cat.
This study explored the prejunctional actions of vecuronium using the in vivo cat soleus nerve-muscle preparation. Vecuronium doses of 1 to 5 micrograms/kg iv suppressed the repetitive firing of the motor nerve endings, and the obligatory potentiation of the twitch response following high-frequency conditioning at 400 Hz for 10 s without attenuating neuromuscular transmission at 0.4 Hz. It was also found that extremely low doses of vecuronium had excitatory effects at the cat soleus motor nerve endings: doses of 0.5 and 1 microgram/kg iv evoked a modest postdrug repetitive firing of the nerve endings and a concomitant potentiation of the muscle responses. These dose-related agonist and antagonist activities suggest that at the motor nerve endings, vecuronium is a weak partial agonist. The major action of vecuronium at the motor nerve endings, however, was suppressive, and this antagonist action contributed to the neuromuscular blocking action of this muscle relaxant.
D000200:Action Potentials; D000818:Animals; D002415:Cats; D005260:Female; D008297:Male; D009045:Motor Endplate / Q000187:drug effects; D009046:Motor Neurons / Q000187:drug effects* / Q000502:physiology; D009119:Muscle Contraction; D009469:Neuromuscular Junction / Q000187:drug effects*; D009435:Synaptic Transmission; D014673:Vecuronium Bromide / Q000494:pharmacology*
D014673:Vecuronium Bromide