Amyloid-beta (Aβ) peptides are the major neuropathological hallmarks related with Alzheimer's disease (AD). Aβ peptides trigger several biochemical mechanisms of neurotoxicity, including neuroinflammation and glutamatergic neurotransmission impairment. Guanosine is the endogenous guanine-derived nucleoside that modulates the glutamatergic system and the cellular redox status, thus acting as a neuroprotective agent. Here, we investigated the putative neuroprotective effect of guanosine in an AD-like mouse model. Adult mice received a single intracerebroventricular injection of Aβ1-40 (400 pmol/site) or vehicle and then were treated immediately, 3 h later, and once a day during the subsequent 14 days with guanosine (8 mg/kg, intraperitoneally). Aβ1-40 or guanosine did not alter mouse locomotor activity and anxiety-related behaviors. Aβ1-40-treated mice displayed short-term memory deficit in the object location task that was prevented by guanosine. Guanosine prevented the Aβ1-40-induced increase in latency to grooming in the splash test, an indicative of anhedonia. Aβ1-40 increased Na+-independent glutamate uptake in ex vivo hippocampal slices, and guanosine reversed it to control levels. The repeated administration of guanosine increased hippocampal GDP levels, which was not observed in the group treated with Aβ plus guanosine. Aβ1-40 induced an increase in hippocampal ADP levels. Aβ1-40 decreased GFAP expression in the hippocampal CA1 region, an effect not modified by guanosine. No differences were observed concerning synaptophysin and NeuN immunolabeling. Together, these results show that guanosine prevents memory deficit and anhedonic-like behavior induced by Aβ1-40 that seem to be linked to glutamate transport unbalance and alterations on purine and metabolite levels in mouse hippocampus.
Keywords: Alzheimer’s disease; Anhedonia; Aβ1–40; Glutamate transport; Guanosine; Learning and memory.