Figure 1.

Pharmacological characterization of candoxin using the chick biventer cervicis muscle (a, b) and comparison of the blockade of nerve-evoked twitch responses produced by candoxin in various isolated nerve-muscle preparations (c). (a) The effects of candoxin (10, 30 and 100 μg ml⁻¹) on twitch responses evoked by nerve stimulation (Nerve); twitch responses evoked by direct muscle stimulation (Muscle) and contractures produced by ACh (300 μM), CCh (8 μM) and KCl (30 mM) in the chick biventer cervicis muscle. The responses of the muscle to candoxin are expressed as a percentage of the respective control values in the absence of candoxin. Values are mean±s.e.m., n=6. Vertical bars represent the s.e.m. (b) Concentration-dependent blockade of nerve-evoked twitch responses of the chick biventer cervicis muscle produced by candoxin, erabutoxin-b, α-bungarotoxin and α-cobratoxin. The time taken to produce 90% twitch blockade is shown. Each data point is the mean of six experiments. The vertical bars represent the SEM. (c) The concentration-dependent blockade of nerve-evoked twitch responses produced by candoxin in the chick biventer cervicis muscle (n=10), mouse phrenic nerve hemidiaphragm (n=8) and GPD (n=8) is shown. The time to produce 90% twitch blockade in the respective nerve-muscle preparations is shown. Vertical bars represent the s.e.m. *P<0.001, significantly different from control.