ON FINE STRUCTURE OF SYNAPSES IN CENTRAL NERVOUS SYSTEM OF INSECTS

The fine structure of synapses in the neuropil of insect (Formica lugubris Zett.) ganglia has been further investigated. The presence of axo-axonic junctions is demonstrated in simplex form as well as in so-called dyades" resembling the ones in vertebrate retina. These dyades are characterized by a T-shaped presynaptic dense projection. The clear synaptic vesicles react positively to zinc iodide osmium stain. The efficiency of PTA block staining for the demonstration of synaptic junctions in the insect neuropil is remarkable. Two extreme architectural patterns of neuropil are described: one in which the presynaptic profiles prevail and the opposite in which a few large presynaptic end bulbs are surrounded by a vast number of postsynaptic elements. © 1969 Springer-Verlag."