Despite significant progress in understanding of the potential of
adenosine A1 receptor-based
therapies in treatment of
cerebral ischemia and
stroke, very little is known about the effect of selective stimulation of
adenosine A2A receptors on the outcome of a cerebrovascular arrest. In view of a major role played by
adenosine A2 receptors in the regulation of cerebral blood flow, we have investigated the effect of both acute and chronic administration of the selective
adenosine receptor agonist 2-[(2-aminoethylamino)-carbonylethylphenylethylamino]-5'-N- ethylcarboxoamidoadenosine (APEC) and antagonist
8-(3-chlorostyryl)caffeine (CSC) on the outcome of 10 min
ischemia in gerbils. Acute treatment with APEC improved recovery of postischemic blood flow and survival without affecting neuronal preservation in the hippocampus. Acute treatment with CSC had no effect on the cerebral blood flow but resulted in a very significant protection of hippocampal neurons. Significant improvement of survival was present during the initial 10 days postischemia. Due to subsequent deaths of animals treated acutely with CSC, the end-point mortality (14 days postischemia) in this group did not differ statistically from that seen in the controls. It is, however, possible that the late mortality in the acute CSC group was caused by the systemic effects of
brain ischemia that are not subject to the treatment with this
drug. Chronic treatment with APEC resulted in a statistically significant improvement in all studied measures. Although chronic treatment with CSC improved postischemic blood flow, its effect on neuronal preservation was minimal and statistically insignificant. Mortality remained unaffected. The results indicate that the acute treatment with
adenosine A2A receptor antagonists may have a limited value in treatment of global
ischemia. However, since administered CSC has no effect on the reestablishment of postischemic blood flow, treatment of
stroke with
adenosine A2A receptor antagonists may not be advisable. Additional studies are necessary to elucidate whether chronically administered drugs acting at
adenosine A2 receptors may be useful in treatment of
stroke and other
neurodegenerative disorders.