Time course of acetylcholinesterase inhibition in the medulla oblongata of the rat by O-ethyl S-(2-dimethylaminoethyl) methylphosphonothioate in vivo.

1. The time course of acetylcholinesterase inhibition in three parts of the medulla oblongata of the rat following intramuscular injection of O-ethyl S-(2-dimethylaminoethyl) methylphosphonothioate was studied.2. The inhibition in the three parts of the medulla oblongata proceeded at different rates and this indicates that penetration of the inhibitor through various parts of the blood-brain barrier is not uniform.