TRANSPLANTED EMBRYONIC ENTORHINAL NEURONS MAKE FUNCTIONAL SYNAPSES INADULT HOST HIPPOCAMPUS

Grafts of embryonic entorhinal cortex (EC) or non-entorhinal cortex (N EC) were placed into the hippocampus of adult rats with transection of the perforant paths. Graft-host connectivity was investigated at 4-6 months post-transplantation by recording extracellular evoked response s in hippocampal slice preparations. Electrical stimulation of the gra fts evoked excitatory postsynaptic potentials (EPSPs) in the outer mol ecular layer of the dentate gyrus, and the stratum lacunosum molecular e of CA1, CA3, and elicited population spikes in the granule cell laye r and the pyramidal cell layer of CA1, but not CA3. While the latencie s and the forms of these evoked response were similar to those in matc hed control slices from the normal animals, the amplitudes were smalle r than normal controls. However, in the slices with NEC grafts, no suc h responses were recorded when stimulus was applied in similar positio n in the grafts. The findings suggest that grafted entorhinal neurons make viable synaptic connections with the host hippocampus. (C) 1998 E lsevier Science B.V.