Young (3 months old) and aging (18-21 months old) rats were infused intracerebroventricularly with beta-amyloid (1-40; 4.2 nmol) for 14 days. In both age groups, beta-amyloid led to deficits in water-maze and decreased choline acetyltransferase activity and somatostatin levels. Cortical substance P levels also decreased whereas neuropeptide Y levels remained unaltered. There were no significant age dependent differences among these neurochemicals except a decrease in hippocampal neuropeptide Y levels in the aging group. It is concluded that young and aging rat brains respond similarly to beta-amyloid infusion.