The selective block of adenosine A2Breceptors prevents neuronal death in CA1 hippocampus after oxygen glucose deprivation

Cerebral ischemia results from severe reduction in cerebral blood flow after cardiac arrest, occlusion of vessels supplying nervous tissues, or prolonged systemic hypotension. Each year about 700,000 people suffer new or recurrent stroke, a major cause of long-term disability, and the third most common cause of death in Western countries. The availability of drugs able to counteract stroke induced neurodegeneration is still an unmet need. Extracellular concentrations of adenosine significantly increase during cerebral ischemia [1] reaching the μmolar range, thus activating all four adenosine receptor subtypes: A1, A2A, A2B, and A3. The role of adenosine A1, A2A and A3 receptors was already investigated in the in vitro model of “severe ischemia” induced by 7 min of oxygen and glucose deprivation (OGD) in the CA1 region of rat hippocampal slices [2]. No data on the involvement of A2B receptor in this model of cerebral ischemia are so far available. In this work we investigated the role of the adenosine A2B receptor during OGD by the use of a selective antagonist ofthe A2B receptor, PSB 603. The OGD-induced cell injury and PSB 603 effect on the extent of CA1 pyramidal neuron injury was assessedby immunohistochemistry for NeuN (a typical neuronal cell body marker), in hippocampal slices fixed in paraformaldehyde 1 h after the end of OGD. The severe ischemic insult caused substantial damage to CA1 pyramidal neurons, as determined by the reduction in NeuN fluorescence that is indicative of a decrease in the number of neurons. In addition, a significant increase of pyknotic nuclei (+696%, n = 7; p = 0.0010) and of degenerating, a-nucleated neurons (+1400 %, n = 7; p = 0.0009) were found in OGD-untreated slices in comparison to control slices. These effects were completely prevented by the antagonist PSB 603 (50 nM, n = 7). OGD did not affect astrocytes or microglia, at least at 1 h after the end of OGD. Results show for the first time that selective antagonism of adenosineA2Breceptor improves neuronal survival following a severeOGD period in the CA1 hippocampus.