By immunohistochemistry, Fos-like protein induced in response to intrastriatal kainic acid injections was explored in the basal ganglia and the ventrolateral thalamic nucleus of the rat. In the globus pallidus, entopeduncular nucleus, substantia nigra pars reticulata, subthalamic nucleus and ventrolateral thalamic nucleus, Fos was expressed in neuronal cell nuclei showing the maximal number at 4 h and disappeared within 48 h. The substantia nigra pars compacta neurons lacked prominent Fos induction, suggesting that a different mechanism may operate for changes of dopamine systems. Concurrent Fos expression noted in selected regions suggests the link of relay and output stations of the basal ganglia with the ventrolateral thalamus at the early stage of striatal cell degeneration.