Intrathecal injections of kainic acid and sodium chloride were performed in rats to study the cellular modifications observed in spinal cord. Early neuronal changes (2 and 24 h) associated dark and shrunken or swollen and vacuolated cytoplasms. Delayed (3, 6, 14 days) changes, mainly consisted in degenerative aspect of motoneurons with eccentric and indented nucleus, swollen cytoplasms with proximal neurite enlargements, the presence of 'lipofuscin-like' pigments, disorganized intracytoplasmic organelles and filament accumulations.