Ultrastructure of different neuropil zones of the procerebrum in snails and slugs

Ultrastructure and peculiarities of interneuronal connections in various zones of neuropil of procerebral olfactory centers of the brain in snails and slugs: in the outer and inner neuropil, zone of input of afferent fibers of labial nerves, as well as zones of running of afferent and efferent fibers of tentacular nerves, were studied. A pronounced spatial morpho-functional differentiation and a complex zonal synaptoarchitectonics of procerebrums is revealed. It has been shown that the procerebrum neural elements, both intrinsic and numerous ones coming from other brain regions and chemosensory systems, contain an enormous variety of vesicles. These vesicles provide connections between neural elements in various synapses and synapse-like junctions and in the composite divergent and convergent complexes formed by them. A positive polychemical nature of granular cells, the main neural elements of procerebrums, and functional significance of symmetric junctions predominant in procerebrums is discussed.