Conditioned blocking is re-established by neurotransplantation in mature rats

Aging has been associated with a decay of hippocampal function that may beg in well before senescence. Conditioned blocking is a complex learning pheno menon that requires an intact hippocampus in young-adult rats and is absent in middle-aged rats. The aim of the present study was to test the possibil ity of re-establishing conditioned blocking in 17-month-old Wistar rats by neurotransplantation. Solid embryonic hippocampal or nigral tissue was bila terally transplanted in the proximity of the dorsal hippocampus (lateral ve ntricle and alveus). Conditioned blocking of an aversion to a cider vinegar (31%) solution presented in compound with a previously conditioned sacchar in solution (0.1%) appeared 14 days after transplantation and persisted 3 m onths later only in the hippocampal grafted group, showing the possibility of restoring age-related cognitive deficits. NeuroReport 12:2297-2301 (C) 2 001 Lippincott Williams & Wilkins.