Acetylcholinesterase activity, choline acetyltransferase and GABA immunoreactivity in the ventral horn of the spinal cord of rats during chromatolysis

A comparative study on the changes of the acetylcholinesterase activity (AChE) and of choline acetyltransferase (ChAT)- and GABA-like immunoreactivity (LI) has been performed in the ventral horn cells of the spinal cord of white rats 1, 2 and 3 weeks after transection of the right sciatic nerve. For the visualization of the AChE the method of Karnovsky and Roots (1964) was used. ChAT-LI was demonstrated by means of the avidin-biotin-peroxidase complex method (Hsu et al., 1981), whereas GABA-LI was localized using the PAP-method of Sternberger et al. (1970). In the control rats AChE-activity was observed on the cellular membrane, weaker in the cytoplasm of the perikarya and the proximal processes of the motoneurons; a pericellular localization of the reaction product was also established. ChAT-like immunoreactivity was mainly observed in the cytoplasm of the perikarya and the cellular processes, whereas GABA-like was most intensive in the nuclei of a number of motoneurons and in the more distal parts of their dendrites; the staining intensity of the perikaryal cytoplasm was weaker. During chromatolysis a progressive decrease of the staining intensity of the reactions for all the 3 substances was observed. In some neurons there was a total loss of the immunoreactivity. These results suggest that during chromatolysis: 1. the production of acetylcholine and GABA decreases; 2. the GABA which coexists within some cholinergic motoneurons may be expressed by these cells and 3. the AChE activity may also in the future be used as a marker of the cholinergic system of the anterior horn cells of the spinal cord.