Kainate-induced seizures lead to marked increases of alpha-tubulin mRNA and protein immunoreactivity in the rat dentate gyrus. The increase in alpha-tubulin mRNA was restricted to the granule cell bodies. alpha-Tubulin immunoreactivity was enhanced in granule cell dendrites and axons (the mossy fibers), in the molecular layer. These changes peaked 6-12 days after kainate treatment and preceded the collateral sprouting of mossy fibers which occur 12 to 30 days after seizures. The present results suggest that microtubule formation contributes to the synaptic rearrangements which take place in the hippocampus after seizures.