The effects of lesioning mesostriatal dopamine projections or striatal neurons on tachykinin binding in the basal ganglia were assessed in the rat. 6-Hydroxydopamine lesions of the medial forebrain bundle destroyed striatal dopamine terminals as assessed by [3H]mazindol autoradiography, but did not significantly affect the binding of NK-1 ([3H][Sar9,Met(O2)11]substance P) or NK-3 ([3H]senktide) tachykinin ligands in the striatum. 6-Hydroxydopamine lesions significantly reduced NK-3 binding in the substantia nigra pars compacta, but not the ventral tegmental area. In contrast, striatal quinolinic acid lesions reduced both NK-1 and NK-3 binding in the striatum, but failed to affect NK-3 binding in the substantia nigra. These findings suggest that both NK-1 and NK-3 receptors within the striatum are predominantly post-synaptic with respect to dopamine neurons, whereas nigral NK-3 receptors are located on dopaminergic neurons.