Immunohistochemical localization of N-methyl-D-aspartate and alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate receptor subunits in the substantianigra pars compacta of the rat

Ionotropic glutamate receptors in the substantia nigra pars compacta regula te the activity of dopamine neurons. We have used dual-label immunofluorese nce 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 glutama te receptor 2/3 was prominent in the soma and proximal dendrites of all tyr osine 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-aspa rtate receptor 1 present. Immunostaining for the N1, C1 and C2 variably spl iced segments of N-methyl-D-aspartate receptor 1 were scarce in the substan tia nigra pars compacta, while immunoreactivity for the alternative C2' ter minus of N-methyl-D-aspartate receptor 1 was quite abundant. Staining for g lutamate receptor 1 was heterogeneous; about half of the tyrosine hydroxyla se immunopositive cells stained intensely, while the other half were immuno negative. The glutamate receptor 1-stained cells were concentrated in the v entral tier of the substantia nigra pars compacta. Glutamate receptor 4 was nor found in tyrosine hydroxylase-immunopositive cells within the substant ia nigra pars compacta. Together, these data demonstrate that dopaminergic neurons in the substanti a nigra pars compacta express primarily glutamate receptor 1, glutamate rec eptor 2/3 and,N-methyl-D-aspartate receptor 1 isoforms containing the alter native C2' terminus. (C) 1998 IBRO. Published by Elsevier Science Ltd.