[Ultrastructure of synapses in the nucleus of the trapezoid body of the bat].

The subsynaptic structure of the synapses in the medial nucleus of the trapezoid body was studied in the bat Myotis oxygnatus. The synaptic endings in the nucleus are represented by large-cup-shaped and small loop-shaped terminations. The cup-shaped terminations are formed of large branches originating from a thick myelinated fibre after loss of myelin from it. Each branch forms a series of contacts alternating with vast enlargements of extracellular space, on the body of the cell and its processes. Large branches are filled with synaptic vesicles, neurofilaments and neurotubules, mitochondria; all these components are distributed rather regularly along the branch diameter. In fine branches of the cup the synaptic vesicles are the main and often the only component. The pattern of the cup branch changes as the distance from the main fibre increases, namely the amount of neurofilaments and neurotubules diminishes up to their disappearance, while the amount and the density of synaptic vesicles increases. The small loop-shaped treminals are different from the cup-shaped ones by the composition of the synaptic vesicles and the structure of the contact zone. In addition to agranular vesicles there are also granular ones. Both types of terminations--cup-shaped and loop-shaped ones -- are found both on the bodies and dendrites. On distal portions of dendrites the terminations are disposed in nests.