[The ultrastructure of the inferior olivary complex in ground squirrels (Citellus citellus L.). The neuropil. Age-related changes in the axons].

The morphological characteristics of axon terminals among a neuropil in the lower olivary complex of ground squirrels at various ages were studied by an electron microscope. The presynaptic part of the chemical synapses in the glomerular or outside glomerular position among the neuropil pf this nuclear complex were axon terminals and terminals "en passant". These axon elements participate in the formation of crash-like synapses with somatic, dendrite prickles, but also with dendrite adjuncts in the formation of complex synaptic connections. A considerable part of myelin axons and axon terminal were changed in old ground squirrels during all seasons. There were two varieties: 1. axon elements with preserved sizes and dense bodies, myelin-like figures, a large number of mitochondria and glycogen granules were found among normal organoids. 2. myelin and amyelin "spheroids" with various sizes and inner structure. The changes axon elements of the neuropil in the inferior olivary complex of ground squirrels at various ages during all seasons are physiological probably connected with the process of aging.