Assessment of neuromuscular blockade produced by atracurium in frog sartorius muscle.

The neuromuscular effects of atracurium in frog sartorius muscle were studied and the results were compared with those obtained by tubocurarine in the same preparation. Single twitch (at 1 per 5 s) and tetanic stimulation (at 1-100 per s) of the motor nerve, stimulated with 5-10 V (maximum) and 0.2 ms pulse duration, were used to assess the neuromuscular blockade produced by atracurium and tubocurarine in the frog sartorius muscle. The results showed that atracurium was twice as potent as tubocurarine in reducing the amplitude of the indirectly-elicited twitch contractions in the frog sartorius muscle. The mean IC50 values (concentration to produce 50% inhibition of twitch tension) of atracurium and tubocurarine-induced depression of the indirectly-elicited twitch tension were 0.64 +/- 0.1 microM and 1.2 +/- 0.2 microM respectively (means +/- s.e., n = 6, P less than 0.001). Furthermore, atracurium had a shorter time of onset, time to 50% block and time to 95% recovery than tubocurarine.