Disruptions in synaptic plasticity in the dorsal striatum may contribute to the pathophysiology underlying Parkinson's disease. Here we report a novel, chemically-induced form of plasticity induced by application of the potassium channel blocker tetraethylammonium (TEA) in the dorsolateral striatum of the adult rat. Transient application of TEA persistently increased synaptically-evoked extracellularly-recorded corticostriatal responses in an activity-, concentration- and time-dependent manner. Pharmacological experiments suggest that this plasticity is dependent on L-type calcium channel and protein kinase C (PKC) activation. Striatal dopamine depletion induced by nigrostriatal dopamine lesions with 6-hydroxydopamine significantly reduced, but did not abolish, TEA-mediated enhancement of the corticostriatal response. Intracellular recordings demonstrate that this TEA-mediated plasticity is associated with an increase in EPSP size and slope, as well as input resistance. Collectively, these findings demonstrate a novel form of L-type calcium channel-dependent plasticity in the adult dorsal striatum that is induced in the absence of dopaminergic input.