Cholinesterase Content of Certain Regions of the Spinal Cord as Judged by Histochemical and Cartesian Diver Technique

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Abstract
Summary.: 1. The cholinesterase content of neurones belonging to the antero‐lateral group of the anterior horn of the spinal cord of rat has been investigated histochemically by means of a modified thiocholine method and microchemically by means of a Cartesian diver technique.Biochemical controls with the inhibitor (Mipafox) run in solutions similar to those used histochemically have been made.2. When rat brain homogenate was used as source of enzyme, with Mipafox (4 × 10‐6 M) as inhibitor, and ace'ylthiocholine as substrate (0.004 M), the inhibition curve fits between those of AcChE (electric tissue) and BuChE (Cohn's serum fraction).3. A histochemical survey of a section of the cervical cord shows that only anterior and lateral horns are stained. The large motor neurones are heavily stained and the product of the histochemical reaction is clearly visible along the neurites. The difference in staining intensity among various cells is not sufficiently marked to allow a quantitative appreciation of cholinesterase activity.4. By measuring the cholinesterase activity of single neurones by means of the Cartesian diver technique two significantly different groups of cells can be demonstrated. In one group the total enzyme activity per cell is approximately 4 times higher than in the other. All the cells investigated have a measurable cholinesterase activity. Experiments with a selective inhibitor demonstrated that the enzyme present in these cells is acetylcholinesterase.5. The results are discussed in the light of what is known about the morphology and physiology of the motor cell groups of the spinal cord.