Acetylcholinesterase distribution in axotomized frog motoneurons.

The distribution of acetylcholinesterase (AChE; EC 3.1.1.7) activity was examined in the perikarya and proximal axonal stumps of frog motoneurons injured by ventral root transection. Based upon measurements of net AChE accumulation in the proximal stumps of transected ventral roots, and upon orthograde clearances of AChE reported by others, it was determined that an amount of AChE equivalent to at least 0.7-2 times the perikaryal content of this enzyme enters the motor axon each day. A progressive decrease in the rate of AChE accumulation in transected axons during the first 3 days after ventral rhizotomy raised the possibility that excess enzyme might accumulate elsewhere within the axotomized motoneurons. However, AChE accumulation was detected only near the cut ends of the ventral roots and was not appreciably increased within injured motoneuronal cell bodies and proximal dendrites, which were isolated by a new method combining bulk and single-cell isolation techniques. These data suggest that AChE turnover is altered rapidly in response to axonal injury, thereby avoiding large perikaryal accumulations of this enzyme.