Intracellular distribution of molecular forms of acetylcholinesterase in rat brain and changes after diisopropylfluorophosphate treatment.

The subcellular distribution of acetylcholinesterase activities was studied in the striatum and cerebellum of rat brain. The highest percentage of the enzyme activity was found in the crude synaptosomal (P2) fraction, with striatum much higher than cerebellum. On sucrose density gradient centrifugation analyses all the particulate fractions (P1, P2, and P3) showed a major peak of the 10 S form of acetylcholinesterase activity with very little activity of the 4 S form of the enzyme. The 10 S/4 ratio was much higher in striatum than in cerebellum. In the soluble fraction (100,000 g supernatant) the 10 S form was less than the 4 S form in the adult rat brain, but this was reversed in the 6-day-old rat brain. After diisopropylfluorophosphate administration the recovery of acetylcholinesterase molecular forms in various subcellular fractions differed at different recovery periods. These results indicate that the distribution of molecular forms of acetylcholinesterase in rat brain differs in various subcellular fractions, and also the pattern of distribution differs in different regions of the brain as well as in adult and developing brains.