ACETYLCHOLINESTERASE ACTIVITY IN ESERINE-TREATED ASCIDIAN EMBRYOS.

1. The use of specific cholinesterase inhibitors and substrates demonstrated that the enzyme activity in Ciona intestinalis larvae is an acetylcholinesterase. 2. Eggs treated with eserine sulfate (an acetylcholinesterase inhibitor) for one hour prior to fertilization developed into larvae with defective muscular movements and greatly reduced levels of acetylcholinesterase activity. 3. Two kinds of experiments show that this reduced enzyme activity was caused by the retention of eserine and not by inhibition of acetylcholinesterase synthesis. Homogenates of embryos from eserine-treated eggs inhibit acetylcholinesterase activity when mixed with homogenates of control embryos. Full enzyme activity in homogenates of the experimental embryos could be recovered by dialysis.