AUTORADIOGRAPHIC ANALYSIS OF 2ND-MESSENGER SYSTEMS IN THE GERBIL HIPPOCAMPUS FOLLOWING REPEATED BRIEF ISCHEMIC INSULTS

Using [H-3]inositol 1,4,5-triphosphate (IP3), [H-3]phorbol 12,13-dibutyrate (PDBu) and [H-3]forskolin, we performed quantitative autoradiography to determine sequential alterations in second-messenger systems in the gerbil hippocampus following repeated brief ischemic insults. Changes following three 2-min ischemic insults were compared with those following single 2- or 6-min ischemia. [H-3]IP3 binding was extremely sensitive to ischemic insult, and more than 80% of the binding sites were lost after destruction of CA1 pyramidal cells following 6-min ischemia and three 2-min ischemic insults. Furthermore, a 30% reduction was observed after 2-min ischemia which leads to no neuronal loss. [H-3]PDBu binding in the CA1 subfield decreased by 1 day after three 2-min ischemic insults and by 4 days after 6-min ischemia, and 40-50% reductions were observed at 1 month. In contrast, [H-3]forskolin binding was relatively preserved. [H-3]PDBu and [H-3]forskolin binding transiently increased early in the reperfusion period. We also observed a difference in the pattern and severity of alterations between repeated ischemic insults and single ischemia.