Ionotropic glutamate receptors in the substantia nigra pars compacta regulate the activity of dopamine neurons. We have used dual-label immunofluoresence and confocal laser microscopy to study the localization of subunits of two types of ionotropic receptors within the substantia nigra pars compacta of the rat. Immunostaining for N-methyl-D-aspartate receptor 1 and glutamate receptor 2/3 was prominent in the soma and proximal dendrites of all tyrosine hydroxylase-immunopositive cells, while only low amounts of N-methyl-D-aspartate receptor 2A and N-methyl-D-aspartate receptor 2B were present. Selective antibodies were used to determine the isoforms of N- methyl-D-aspartate receptor 1 present. Immunostaining for the N1, C1 and C2 variably spliced segments of N-methyl-D-aspartate receptor 1 were scarce in the substantia nigra pars compacta, while immunoreactivity for the alternative C2' terminus of N-methyl-D-aspartate receptor 1 was quite abundant. Staining for glutamate receptor 1 was heterogeneous; about half of the tyrosine hydroxylase immunopositive cells stained intensely, while the other half were immunonegative. The glutamate receptor 1-stained cells were concentrated in the ventral tier of the substantia nigra pars compacta. Glutamate receptor 4 was not found in tyrosine hydroxylase-immunopositive cells within the substantia nigra pars compacta. Together, these data demonstrate that dopaminergic neurons in the substantia nigra pars compacta express primarily glutamate receptor 1, glutamate receptor 2/3 and N-methyl- D-aspartate receptor 1 isoforms containing the alternative C2' terminus.