DENERVATION DECREASES THE IPSILATERAL EXPRESSION OF ACHE IN CHICK LUMBARIC MOTOR-NEURONS

In vertebrate neuromuscular junctions, acetylcholinesterase (AChE; EC 3.1.1.7) is highly concentrated at the synaptic basal lamina and the p ostsynaptic muscle fiber. The postsynaptic muscle cell is the primary source of AChE. However, several lines of evidence indicate that the p resynaptic motor neuron is able to synthesize and secrete AChE at the neuromuscular junctions. By using anti-AChE monoclonal antibody in imm unohistochemical staining, we found that the AChE-positive cells were labeled only at the motor neurons of the chick spinal cords. When the protein extract of chick spinal cords was analyzed by a Western blot a nalysis, a protein band of similar to 105 kDa was recognized. In dener vated chicks, the expression of motor neuron AChE, as recognized on a Western blot, decreased by similar to 50% 4 days after denervation. Th e AChE expression in denervated chick spinal cords, however, was resto red to control level 10 days after denervation. The decreased AChE exp ression was restricted to the ipsilateral side of the denervated chick spinal cord while the contralateral side was relatively unchanged. In comparison with the contralateral side, the level of AChE protein and enzymatic activity expressed in the ipsilateral spinal cord was simil ar to 50% lower. This is the first demonstration to show that the ipsi lateral and contralateral sides of chick spinal cords respond differen tly after nerve denervation. (C) 1997 Elsevier Science Ireland Ltd.