Guanosine Neuroprotective Action in Hippocampal Slices Subjected to Oxygen and Glucose Deprivation Restores ATP Levels, Lactate Release and Glutamate Uptake Impairment: Involvement of Nitric Oxide

Stroke is a major cause of disability and death worldwide. Oxygen and glucose deprivation (OGD) in brain tissue preparations can reproduce several pathological features induced by stroke providing a valuable ex vivo protocol for studying the mechanism of action of neuroprotective agents. Guanosine, an endogenous guanine nucleoside, promotes neuroprotection in vivo and in vitro models of neurotoxicity. We previously showed that guanosine protective effect was mimicked by inhibition of nitric oxide synthases (NOS) activity. This study was designed to investigate the involvement of nitric oxide (NO) in the mechanisms related to the protective role of guanosine in rat hippocampal slices subjected to OGD followed by reoxygenation (OGD/R). Guanosine (100 mu M) and the pan-NOS inhibitor,l-NAME (1 mM) afforded protection to hippocampal slices subjected to OGD/R. The presence of NO donors, DETA-NO (800 mu M) or SNP (5 mu M) increased reactive species production, and abolished the protective effect of guanosine orl-NAME against OGD/R. Guanosine orl-NAME treatment prevented the impaired ATP production, lactate release, and glutamate uptake following OGD/R. The presence of a NO donor also abolished the beneficial effects of guanosine orl-NAME on bioenergetics and glutamate uptake. These results showed, for the first time, that guanosine may regulate cellular bioenergetics in hippocampal slices subjected to OGD/R injury by a mechanism that involves the modulation of NO levels.