D3 dopamine receptors interact with dopamine D1 but not D4 receptors in the GABAergic terminals of the SNr of the rat

► Activation of dopamine D3 receptors in striatonigral terminals potentiated the D1 receptor-induced increase in GABA release. ► Dopamine D3 receptor activation alone didn't modify GABA release. ► In SNr, D3 receptors modulate GABA release mainly by interacting with the D1 receptors of striatonigral projections.