Ultrastructural Changes in Neurons and Synapses of the Dentate Area Accompanying Long-term Potentiation Induced by Perforant Path Stimulaton

Abstract

Repeated high-frequency stimulation of the perforant path results in an enhancement in the population EPSP and population spike recorded in the dentate area. Morphological investigations have been performed to study the ultrastructural changes in neurons and synapses of the dentate gyrus accompanying the development of longterm potentiation. Long-term potentiation induces a long-lasting increase of the number of shaft synapses (axo-dendritic synapses) in the dentate molecular layer, and results in an enhancement of the ribosomes of the granule cell cytoplasm. These facts could reflect the relatively long-lasting shifts in the neuronal connectivity accompanied by an activated protein synthesis following long-term potentiation.