Restoration of High Affinity Choline Uptake in the Hippocampal Formation Following Septal Cell Suspension Transplants in Rats with Fimbria-Fornix Lesions

High affinity choline uptake (HACU) was investigated in the hippocampal formation following fetal septal cell suspension transplants into rats with fimbria-fornix lesions. Nine-14 weeks after transplantation, HACU was markedly decreased in hippocampi from animals with fimbria-fornix lesions; this decrease was ameliorated by fetal septal cells transplanted into the host hippocampus. HACU related to septal transplantation was activated in vitro by K+, and in vivo by the administration of scopolamine and picrotoxin. These findings suggest that fetal septal cell transplantation can restore HACU in the host hippocampus following fimbria-fornix lesions, and that HACU related to the graft has pharmacological properties similar to those of the normal adult HACU system. The activation of HACU by picrotoxin, a gamma-aminobutyric acid (GABA) antagonist, suggests that transplanted cholinergic neurons receive either direct or indirect functional input from GABAergic afferents from the transplant and/or host hippocampus. Lesions of the fimbria-fornix also resulted in an increased binding to muscarinic receptors in the dorsal hippocampus. This increase in binding was not significantly ameliorated by intrahippocampal grafts of cholinergic neurons.