The effects of endothelin 1 (ET-1; 300 pmol/rat intracarotid) on somatosensory evoked potential were investigated in rats. ET-1 led to an amplitude reduction, peak latency prolongations and waveform disturbances. There was a large interindividual variability. The late cortical components were more affected than the earlier potentials at a thalamic or cortical level. ET-1-induced SEP changes developed quickly after the drug injection and persisted for at least 30 min. It is assumed that the observed effects probably reflect the occurrence of a progressively developing ischemia subsequent to ET-1 administration. Moreover, the pattern of ET-1-induced changes suggests a greater sensitivity of the synaptic transmission to the ischemic influence than the axonal conduction.