On the heterogeneity of Purkinje neurons in vertebrates. Cytochemical and morphological studies of chromatin during eel (Anguilla anguilla L.) life cycle.

The relationship between the heterogeneity of Purkinje cell chromatin and the functional involvement of cerebellum has been analyzed comparing two stages of eel life cycle (yellow eel and silver eel) which are characterized by a different degree of swimming activity. The DNA content and the chromatin condensation have been studied by means of microdensitometry (Feulgen-DNA, Feulgen-DNA/area), microfluorometry (DNA after intercalation with Propidium Iodide at low and high concentration) and electron microscopy. In the transition from the yellow eel to the silver eel, the Purkinje cell heterogeneity undergoes variations. In the silver eel, which shows a higher swimming activity, high Feulgen-DNA and Propidium Iodide-DNA (H2c to 4c) were more frequent and a greater heterogeneity in the chromatin condensation was observed. In particular, the changes were more evident in the lobus vestibulolateralis; mainly in this area, which receives inputs from the lateral line, the Purkinje cells are scattered in the molecular layer. On the contrary, in the yellow eel these large cells occupy the zone near or within the granular layer. The data suggest a relationship between the degree of heterogeneity of Purkinje cells and the afferent systems of the cerebellar areas examined. The changes of cerebellar cytoarchitectonics may be expression of the higher degree of the swimming activity of silver eel.