Involvement of Adhesive Puncta Adherentia Type Junctions in the Formation of Synaptic Connections between Dentate Fascia Transplants and the Recipient Brain

Abstract

The dentate fascia of 20-day Wistar rat fetuses were transplanted heterotopically into the somatosensory area of the neocortex of adult rats. Granule cells in grafts projected their axons (mossy fibers) into recipient brains and established synaptic contacts with inappropriate targets. Electron microscopy was used to study the characteristics of the organization of ectopic mossy fiber synapses. These studies showed that ectopic synapses reproduced the determinant structural features of giant hippocampal synapses and induced subcellular reorganization of postsynaptic dendrites in the neocortex. Morphometric analysis showed significant increases in the number and extents of adhesive junctions, puncta adherentia, in ectopic synapses as compared with controls. These data indicate the involvement of adhesive mechanisms in the structural-chemical adaptation of target neurons to foreign axons growing from transplants.