[Sampling of tissue from microscopic areas of the spinal cord of the chick embryo. Description of the technic and application to the study of enzymes metabolizing acetylcholine].

In the present communication we describe a very simple procedure which allows measuring the specific activity of cholinergic enzymes (Acetylcholinesterase and cholinacetyltransferase) in microscopical areas of chick embryo spinal cord. Microhomogenates were prepared as follows: i) a number of fresh cryostat sections (20 mu thick) were stained with toluidine blue; ii) the adjacent unstained sections were microdissected under stereomicroscope and tissue fragments were collected from different areas (lateral, medial and posterior columns; anterior, lateral and posterior bundles). Tissue fragments were dissolved in 10 mM sodium-phosphate buffer pH 7.4 (20-40 sections). Protein assay was performed according to Bradford (1976). AChE and ChAc were measured by radiochemical methods of Fonnum (1969, 1970). In lumbar segments of 18-day chick embryo spinal cord AChE was found in all structure investigated, by contrast ChAc was localized almost exclusively in lateral somatomotor comumns. This result indicates that ChAc can be considered a specific marker for motoneurons. The ontogeny of the cholinergic enzymes in various areas of the chick embryo spinal cord has been investigated.