Alterations in the binding of the phosphodiesterase inhibitor, rolipram, after transient ischemia in the gerbil brain

To determine ischemia-induced changes in phosphodiesterase (PDE), changes in the membranous binding sites of rolipram, a cAMP-selective PDE inhibitor, were examined in the gerbil brain following transient 5 min forebrain ischemia. Coinciding with the delayed neuronal death (DND) in the hippocampal CA1 region, affinities for cerebral rolipram bindings decreased on Day 4, when intrinsic cAMP, substrate for PDE, might increase. The number of rolipram binding sites was significantly reduced in the hippocampus on Day 14, despite the lack of change on Day 4. This reduction in rolipram binding was in agreement with the previously reported late onset reduction of muscarinic receptors, progressing more slowly than DND. Slowly progressive mechanisms may be involved in the ischemia-induced reduction of the hippocampal rolipram binding sites which may be PDEs.