Movement of choline acetyltransferase in axons disconnected from their cell bodies.

1. Phrenic nerves of rats were cut out and divided into two parts of equal length, one proximal and one distal. The activity of choline acetyltransferase of the two pieces was estimated. Four groups of rats were studied: (1) normal rats, and rats in which 3 days earlier, (2) the right nerve had been cut in the uppermost part of the thorax, (3) a ligature had been tied round the right nerve just above the diaphragm, and (4) these two procedures had been combined.2. In normal rats the activity of the enzyme was about the same in proximal and distal pieces. Ligation of the nerve caused an increase of the activity, of about 50%, in the distal but not in the proximal segment.3. After section of the nerve the activity below the section was 18% of normal in the proximal, and 9% in the distal piece.4. When the nerve was both cut and tied the activity decreased to the same level in both pieces, and this was about the level of the proximal piece after mere section of the nerve.5. It is concluded that choline acetyltransferase can move for some time along the axons to the nerve terminals even when the connexion with the soma has been interrupted.