CHOLINE ACETYLTRANSFERASE ACTIVITY IN LARGE VENTRAL SPINAL NEURONS

Abstract— Up to approx 3 pmol of acetylcholine (ACh)/h/cell body was synthesized by perikarya of large spinal neurons isolated in bulk fractions from bovine ventral spinal cord. Many of the cell bodies are probably derived from motoneurons. A medium of low ionic strength and pH was used to minimize losses of soluble acetyl CoA:choline- o -acetyltransferase (ChAc; EC 2.3.1.6) from the neurons, whose permeability properties were altered. Such a medium also increased the retention of other soluble proteins by the cell bodies. The maximal rate of hydrolysis of ACh by the isolated neurons exceeded that of its synthesis by a factor of at least 100. It was estimated that ChAc and acetylcholinesterase (AChE; EC 3.1.1.7) each represent less than 0.01% by weight of the total protein in these cell bodies and that as little as 10% of each enzyme in the ventral spinal cord is located within the large neuronal somata and their proximal processes.