Propionyl-IIGL tetrapeptide antagonizes β-amyloid excitotoxicity in rat nucleus basalis

A putative tetrapeptide beta-amyloid (Abeta) antagonist (propionyl-Ile-Ile-Gly-Leu [Pr-IIGL]) based on the [31-34] sequence of Abeta was previously shown to rescue astrocytes from Abeta-induced membrane depolarization and subsequent long-term elevations of the intracellular Ca2+ concentration in vitro. Here we provide in vivo evidence that the Pr-IIGL tetrapeptide effectively attenuates the excitotoxic action of Abeta(1-42) on cholinergic neurons of the rat magnocellular nucleus basalis (MBN). We also demonstrate by means of microdialysis that administration of Pr-IIGL abolished Abeta(1-42)-induced increases in extracellular aspartate and glutamate concentrations in the MBN, which coincide with a significant preservation of cholinergic MBN neurons and their cortical projections. This neuroprotective effect was associated with preserved exploratory behavior in an open-field paradigm, and improved memory retention in a step-through passive avoidance task. Our data presented here indicate for the first time the efficacy of short, modified functional Abeta antagonists in ameliorating Abeta excitotoxicity in vivo.