Effects of cytochalasin B and vinblastine on the release of acetylcholine from a sympathetic ganglion

The rate of release of acetylcholine from the in vitro superior cervical ganglion of the rat was measured during periods of electrical stimulation both before and after exposure to a drug. Cytochalasin B inhibited the release of acetylcholine in this preparation. Two stages of inhibition were observed. The first, which reduced the rate of release to 20% of control values, was produced by incubating the ganglion for 60 min in solutions containing cytochalasin B. Half-maximal inhibition was observed at concentrations of 3 × 10^?6 M. This stage was not reversed within several hr after cytochalasin B was removed. Uptake of calcium in the first stage was inhibited by cytochalasin B by a small but statistically insignificant amount (13%). The second stage, in which release was further reduced to zero, required both repeated changes of bathing solutions containing cytochalasin B and continual electrical stimulation during the 60 min period of exposure. The second stage was reversed 20–40 min after the drug was removed. It is suggested that the first stage inhibition involves a direct action of cytochalasin B upon the release of acetylcholine from the presynaptic terminal, while the second stage inhibition may be caused by a decrease in the supply of energy to the ganglion. Vinblastine at concentrations of 2.0 × 10^?6 and 1.2 × 10^-4M was also studied using the same experimental procedure. Vinblastine did not inhibit the electrically stimulated release of acetylcholine.