Inhibition of axonal transport in vitro in frog sciatic nerves by chlorpromazine and lidocaine

Summary The effects of chlorpromazine hydrochloride (CPZ HCl) and prochlorperazin-metansulfonate (PCPZ) on the fast axonal transport of labelled proteins were examined in vitro in a peripheral frog nerve.A 0.1 mM concentration of CPZ HCl and PCPZ reduced the amount of transported proteins by more than 50 per cent. An almost complete block was obtained with a 0.5 mM concentration of these two drugs. The lower concentration hardly affected the protein synthesis. The transport inhibiting effect of 0.1 mM of the drugs was reversible but not that of the higher concentration.The number of microtubuli was strongly decreased and the number of filaments increased at the transport inhibiting concentrations. The ultrastructural changes induced by 0.1 mM of the phenothiazine tranquilizer were largely reversible. The local anesthetics lidocaine (18.3 mM) and tetracaine (3.3 mM) both caused similar changes, i.e. a reduction in the number of microtubuli. No ultrastructural effects were observed after treatment with 1 mM ouabain. These three drugs are known to block the axonal flow in the present system at the above mentioned concentrations.The biochemical and ultrastructural results are discussed in relation to those induced by other drugs affecting axonal transport.The present work was supported by grants from Statens Naturvetenskapliga Forskningsråd (No. 2535-8), C.-B. Nathorsts Vetenskapliga och Allmännyttiga Stiftelser, the Swedish Medical Research Council (B73-12X-2543-05B), H. Hierta's Stiftelse and W. och M. Lundgrens Stiftelse. Thanks are due to Mrs B. Egnér, Mrs E. Fjällstedt, Mrs. E. Norström and Mrs U. Svedin for expert technical assistance.