Altered expression of NPY-Y1 receptors in kainic acid induced epilepsy in rats.

Abstract Kainic acid-induced limbic seizures cause lasting increases in neuropeptide Y (NPY) expression in hippocampal granule cells/mossy fibers. The expression of NPY-Y 1 receptors in these neurons were investigated, using in situ hybridization for Y 1 mRNA and receptor autoradiography with the Y 1 -specific ligand [ 125 I][Pro 34 ]PYY. Six hours after kainic acid-induced seizures, Y 1 receptor mRNA levels decreased by 80% in granule cells and concomitantly increased (by 75%) in CA2 pyramidal neurons. Subsequently, persistent decreases in Y 1 mRNA were seen, both in the stratum granulosum and in CA2. Changes in mRNA concentrations were accompanied by a transient, although non-significant, increase in [ 125 I][Pro 34 ]PYY binding in the molecular layer of the dentate gyrus after 4–6 h which was succeeded by a lasting decrease in binding which indicates a persistent down-regulation of Y 1 receptors in hippocampal areas in kainic acid-induced epilepsy.