Intrahippocampal injections of exogenous beta-amyloid induce postdelay errors in an eight-arm radial maze

Alzheimer's disease is characterized by the progressive loss of short-term memory and the accumulation of large amyloid plaques, the primary core of which is the beta-amyloid 1-40 (beta A4) peptide. It has been suggested that beta A4 plays a causative role in the memory degeneration seen in Alzheimer's patients. The current study was designed to test the effects of bilateral intrahippocampal injections of beta A4 on performance in a radial arm maze foraging task with a delay imposed following the fourth choice. Eight Sprague-Dawley rats were injected with either beta A4 (10(-3) M) or vehicle (HPLC buffer) immediately prior to testing in the maze. Although beta A4 did not impair performance on the predelay choices, it did significantly increase errors immediately postdelay. These results suggest that contrary to previous findings, beta A4 does have acute effects when challenged with a short-term memory load and may play a significant role in some memory deficits seen in Alzheimer's disease.