In 1987, we demonstrated a neuronal protective action of PPF in a gerbil model
of cerebral ischemia (DeLeo et al. 1987). In addition to a decrease of Nissl staining
in the CA1 region of the hippocampus, systemic PPF also inhibited the marked glial
fibrillary acidic protein (GFAP) astrocytic response and selective calcium accumulation
in the transition zone between the hippocampal CA1 and CA3 areas (see
Fig. 2). The most remarkable finding of that study was that treatment with PPF
exerted a protective action against postischemic damage. In an effort to investigate
mechanisms of neuronal protection, the efficacy of PPF was compared with that
of pentobarbital. In contrast to PPF, pentobarbital afforded no protection when
administered 1 h after bilateral carotid occlusion, suggesting divergent drug
mechanisms of PPF and pentobarbital (DeLeo et al. 1988b). Electrophysiological
experiments demonstrated no evidence of a direct depressant action of PPF on
neuronal firing (P. Schubert, unpublished data). In a later study, we determined that
PPF protects hippocampal neurons against ischemic damage in the presence of the
adenosine antagonist theophylline, supporting a non-adenosine-mediated action
(DeLeo et al. 1988a). Interestingly, the mechanism of action of this neuroprotection
has not been clearly delineated and only recently has a novel mechanism been
uncovered (see Sect. 2.1).