Intracellular recording of rat striatal neurons was performed in vitro to investigate posttetanic changes in the excitatory post-synaptic potential (EPSP) elicited by stimulation of the corpus callosum. Tetanic stimulation induced posttetanic potentiation (PTP) in 11 of 12 cells. The PTP decayed in 1-5 min and was followed by either a short or long duration depression of the EPSP in 10 of 12 neurons. The remaining two neurons examined showed a slight enhancement of the EPSP that lasted for 30 min after the tetanus. The group of cells demonstrating short-duration depression (n = 3) were characterized by a decay of the depression to the control level by 15-20 min post-tetanus. The EPSP in the remaining cells showing depression (n = 7) showed a maintained depression for the entire recording session. Blockade of GABAA receptors with bicuculline (30 microM) or NMDA receptors with APV (50 microM) did not effect the induction of long-lasting depression of the striatal EPSP. The data indicates that the corticostriatal pathway can undergo enduring forms of use-dependent synaptic plasticity. This type of synaptic modification may participate in the refinement of movement and contribute to striatal related learning and memory.