Differential expression patterns of mGluR1α in monkey nigral dopamine neurons

The expression pattern of metabotropic glutamate receptor Iα (mGluR1α) was immunohistochemically investigated in substantia nigra dopaminergic neurons of the macaque monkey. In normal monkeys, mGluR1α immunoreactivity was weakly observed in the dorsal tier of the substantia nigra pars compacta (SNc-d) where calbindin-D28k-containing dopaminergic neurons invulnerable to parkinsonian degeneration are specifically located. On the other hand, mGluR1α was strongly expressed in the ventral tier of the substantia nigra pars cornpacta (SNc-v). In monkeys treated with the parkinsonism-inducing drug, I-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), mGluR1α expression was decreased in dopaminergic neurons in the SNc-v that were spared its toxic action. These results suggest that mGluR1α expression may be involved at least partly in the vulnerability of dopaminergic neurons to parkinsonian insults.