ACTIVITIES OF ACETYLCHOLINESTERASE, CHOLINE-ACETYLTRANSFERASE, AND CATECHOLAMINE PRODUCTION IN THE SPINAL-CORD OF THE AXOLOTL AMBYSTOMA-MEXICANUM DURING FORELIMB REGENERATION

Amputation of an axolotl limb causes severance of the brachial nerves, followed by their regeneration into a blastema. It is known that thes e nerves provide a neurotophic factor to blastemal cells. To approach the problem of the response of spinal cord nerve centers to forelimb a mputation, we have studied biosynthetic activities in the nerve center s involved in axonal injury during limb regeneration. We report that t he acetylcholinesterase (AChE) activity in the spinal cord is elevated 2 days (+69%) and 7 days (+28%) after limb amputation compared with l evels in unamputated control animals, but is not significantly elevate d at 3 h or 15 days. The percentages of slow (3.6S and 6.0S) and fast (18S) sedimenting forms of AChE progressively decrease 2 and 7 days af ter amputation, while those of intermediate sedimenting forms (10.5S a nd 14.0S) increase. Fifteen days after amputation, lower molecular wei ght forms return to the control level, but the heavy molecular weight form of AChE is absent as at 7 days; consequently intermediate molecul ar weight forms are in a greater proportion than the other two forms. Choline acetyltransferase activity was measured only 2 days after ampu tation (when AChE was at its highest level). It increases by about 34% with regard to the controls. Adrenaline is higher than controls 2 day s after amputation, while noradrenaline is not significantly modified. The metabolic changes observed in the spinal cord during limb regener ation probably are the result of a general reaction to the stress of a mputation (transection of brachial nerves) and regeneration of nerve f ibers, since similar metabolic activities were observed after a simple denervation of the two unamputated forelimbs.