Decline of tissue noradrenaline under the influence of a mitotic inhibitor.

Abstract

MATERIALS are transported down axons by two processes: a slow process of bulk axoplasmic flow moving at 1–6 mm/day and a fast transport process which is thought to be mediated by neurotubules and moves at 102–103 mm/day1. Drugs such as colchicine, which inhibit mitosis by interfering with the formation of the mitotic spindle, interact also with neurotubules, indicating that the neurotubule and the mitotic spindle may be homologous structures2. Colchicine inhibits both fast3 and slow4 intra-axonal protein transport, suggesting that neurotubules may be associated with both processes. Granules containing noradrenaline are transported down sympathetic nerves by a fast process5 which is inhibited by local application of colchicine6. Vinblastine, a mitotic inhibitor used in the treatment of certain cancers, affects formation of neurotubules7, and we have injected vinblastine intravenously into rats in an attempt to interfere with the intra-axonal transport of noradrenaline in sympathetic nerves generally.