Graft-induced learning impairment despite graft-enhanced cholinergic functions in the hippocampus of rats with septohippocampal lesions.

Effects of aspirative fimbria-fornix lesions and intrahippocampal grafts of fetal septal-diagonal band or hippocampal tissue were examined, in Long Evans female rats, on spontaneous alternation, radial maze learning, hippocampal acetylcholine concentrations and [3H]choline accumulation by hippocampal slices. Septohippocampal damage decreased all of these variables. Septal-diagonal band grafts increased hippocampal acetylcholine levels as well as [3H]choline accumulation of tissue (when incubated for 45 min), but they had no effect on alternation rates and further impaired radial maze performances. No such behavioral and neurochemical effects were observed in rats with hippocampal grafts. Our data suggest that factors other than graft-induced improvement of cholinergic functions in the denervated hippocampus may be involved in the expression of behavioral effects by intrahippocampal acetylcholine-rich grafts.