SEIZURE-LINKED HIPPOCAMPAL PLASTICITY AND PROTECTION AGAINST EXCITOTOXICITY - POSSIBLE ROLE OF THE NEUROPEPTIDE-Y

Background and purpose. - Changes occurring in neuropeptide-Y immunore activity after kainic acid injection in rats and their possible conseq uences on seizure-brain damage were studied. Methods. - First, an intr a-hippocampal kainic acid injection was performed (n = 7), inducing an ectopic and bilateral neuropeptide-Y immunoreactivity in mossy fibers . On the side of the injection, this neuropeptide-Y staining was assoc iated with dramatic neuronal loss whereas, in the contralateral hippoc ampus staining was observed without associated neuronal loss. The CA3 a-b pyramidal cell loss induced by an intra-ventricular kainic acid in jection was then compared between a control group (n = 6) and a pre-co nditioned group (n = 6) characterized by neuropeptide-Y staining in th e mossy fibers obtained by a previous contralateral intra-hippocampal kainic acid injection as described. Results. - In the pre-conditioned group, the CA3 a-b pyramidal cell loss was significantly lower (m = 33 .5 %) than in the control group (m = 86.6 %). The neuropeptide-Y inhib iting the pre-synaptic release of glutamate, glutamate-related epilept ic-brain damage could be reduced when neuropeptide-Y is expressed by g ranulated cells. In conclusion, seizure-linked plasticity could induce a self-protection phenomenon against excitotoxic lesions possibly par tially mediated by de novo neuropeptide-Y mossy fiber expression.