Transport, turnover and distribution of choline acetyltransferase and acetylcholinesterase in the vagus and hypoglossal nerves of the rabbit.

Abstract

Abstract— The transport, distribution and turnover of choline O‐acetyltransferase (ChAc, EC 2.3.1.6) and acetylcholinesterase (AChE, EC 3.1.1.7) in the vagus and hypoglossal nerves were studied in adult rabbits. The enzymes accumulated proximally and distally to single and double ligatures on both nerves and thus indicated both a proximo‐distal and retrograde flow of the enzymes. Double ligature experiments indicated that only 5–20 per cent of the enzymes were mobile in the axon. The rate of accumulation of both enzymes above a single ligature corresponded to the slow rate of axonal flow provided that all the enzymes were mobile, but to an intermediate or fast flow if only a small part of the enzymes was transported. The distribution of ChAc along the hypoglossal neurons was studied and only 2 per cent of ChAc was confined to cell bodies, 42 per cent was localized to the main hypoglossal nerve trunks and 56 per cent to the preterminal axons and axon terminals in the tongue. The ratio of AChE to ChAc was about 3 in the hypoglossal nerve and 32 in the vagus nerve.Transection of the hypoglossal nerve was followed by a decrease in the activity of ChAc in the hypoglossal nucleus and nerve and in the axons and their terminals in the tongue. The activity of AChE decreased in the hypoglossal nucleus and nerve but not in the tongue. The half‐life of ChAc in preterminal axons and terminals of the hypoglossal nerve was estimated to be 16‐21 days from the results obtained on transport, axotomy and distribution of the enzyme. Intracisternal injection of colchicine inhibited the cellulifugal transport of both enzymes and led to an increase in enzyme activity in the hypoglossal nucleus.