[Some observations on the ultramicroscopic organization of specialized connections amongst nervous fibres in the inferior olivary nucleus of the cat]

Some observations have been made on inferior olive specimens in the adult cat, with aldehydes fixation techniques through vascular perfusion suitable for electron microscropy. The results made it possible to recognise five types of vesicular structures present in different nerve endings (differences either in type or in number). A possible topographic organization of synaptic connections, between the afferent endings and the dendritic structures of the inferior olive has been considered and it seems that on every large dendrite, nearer the cell body, there is a development of numerous connection. As such connections give a great deal of information to the dendrites with much much interaction it seems possible that there is modulation in the activation of the postsynaptic element. On the other hand, in the periphery of the dendritic branch, many thin branches seem to make contact with few and large endings; this leads us to believe that the regulations of the information is not based only on the afferences but mainly on distribution, origin and number of the postsynaptic elements. A study of the interdendritic connections and of tubulo-vesicular structures showed that their diameter and dense content have a similar morphology with the big granulated vesicles, visible in the terminals, or along the fibres or, frequently, in the Golgi apparatus.