The in vitro effects of vinblastine and vincristine on the responses of the guinea-pig vas deferens to nerve stimulation.

1. Neither vinblastine nor vincristine (1x10-4M) appeared to cause a specific blockade of transmission through the guinea-pig hypogastric ganglion, since responses to preganglionic nerve trunk stimulation were lost no sooner than responses to postganglionic nerve trunk stimulation. 2. The responses to postganglionic nerve trunk stimulation were blocked by vinblastine or vincristine at a time when responses to stimulation of intramural nerve fibres were little affected. 3. The results do not support the suggestion that inhibition of the exocytotic release of transmitter is responsible for the early in vitro effects of these drugs.