To clarify the cellular localization of neuropeptide-Y receptor subtypes in the dentate gyrus and CA3 sector of the rat dorsal hippocampus and their changes after kainic acid-induced seizures, we used receptor autoradiography to measure [125I]PYY binding to Y1 and Y2 receptors after colchicine treatment. Fifteen days after colchicine infusion in the dorsal hippocampus granule cells and their mossy fibres degenerated while the hilar interneurons and CA3 pyramidal cells were spared. This treatment markedly decreased [125I]PYY binding to Y1 receptors in the molecular layer of the dentate gyrus (-82%) and in the hilus (-70%). [125I]PYY binding to Y2 receptors was reduced by 40% and 48%, respectively, in the CA3 region and in the hilus. Thirty days after kainic acid treatment, [125I]PYY binding to Y1 receptors was decreased by 35% in the molecular layer of the dentate gyrus whereas the binding to Y2 receptors was increased by 116% in the hilus. The effect of colchicine in kainic acid-treated rats indicates that these plastic changes occur selectively on granule cell projections.