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

Abstract: 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 pic‐rotoxin. 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 γ‐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 intrahippo‐campal grafts of cholinergic neurons.