Serotonergic modulation of hippocampal acetylcholine release after long-term neuronal grafting

Adult female rats sustained aspirative fimbria-fornix lesions and, 2 weeks later, received intrahippocampal grafts of fetal septal or mixed septal-rap he cell suspensions. Twenty-four months later, the extracellular concentrat ion of hippocampal acetylcholine (ACh) was determined by microdialysis. Bas al ACh levels (5-65 fmol/5 mu l in sham-operated rats) were strongly reduce d after lesioning (3-7 fmol/5 mu l). In septally transplanted and septal-ra phe co-transplanted rats, hippocampal ACh concentrations were restored to n ear-normal levels (15-25 fmol/5 mu l), indicating long-term functional surv ival of hippocampal transplants. After administration of citalopram (100 mu M by infusion) and fenfluramine (20 mg/kg i.p.), the hippocampal ACh efflu x was increased by 2- to 3-fold in all groups of rats. The relative increas e of ACh was highest in co-transplanted rats, an effect which was possibly due to functional interactions between grafted raphe and septal neurons. Ne uroReport 11:3063-3065 (C) 2000 Lippincott Williams & Wilkins.