The Effect of Nicotine on Intra-Axonal Transport in Cholinergic Motor Neurons of the Rat; Influence of Acutely Administered, Non-Toxic Doses

Abstract

The intra-axonal transport of acetylcholine (ACh) and ACh-metabolizing enzymes in rat sciatic nerves was studied following nicotine treatment. The nicotine was administered in a low dose (30 .mu.g/kg) s.c. every 2nd h for 18-22 h, to mimic the serum-concentrations of a cigarette smoker [human]. Control rats received s.c. injections of the vehicle. The main effects were observed regarding the ACh-esterase (AChE) activity. In unoperated nerves the level was decreased by about 10%. In 12 h crushed nerves the accumulation of enzyme activity proximal to the crush was markedly reduced in the nicotine-treated group, indicating a reduction in amount of proximo-distally transported enzyme activity. The ACh-levels were unchanged except at 12 h postoperatively when a small increase proximal to the crush was observed. The choline-acetyltransferase (CAT) activity in unoperated nerves was similar in both groups of rats; the 7 h accumulation above the crush, however, was somewhat reduced after nicotine treatment. The possible causes of the observed nicotine-induced changes are so far not known.