Although kainate has long been known as a powerful axon-sparing neurotoxin,
the localization and functions of kainate receptors in the CNS are largely
unknown, In the present study we examined the distribution of kainate rece
ptor subunits in the monkey striatum using kainate receptor subunits GluR6/
7 and kainate receptor subunit KA2 subunit antibodies at the electron micro
scope level. We found that kainate receptor subunits GluR6/7 immunoreactivi
ty is expressed not only in neuronal perikarya and dendritic processes, but
also in a large population of terminals which form axospinous and axodendr
itic asymmetric synapses, The ultrastructural features of these terminals r
esembled those of glutamatergic corticostriatal boutons, In contrast, very
few kainate receptor subunit KA2-containing terminals were encountered, Alt
hough the functions of these presynaptic kainate receptors remain to be est
ablished, the present data suggest the possibility that they are located to
modulate the release of glutamate from cortical afferents in the monkey st
riatum, and that an abnormal regulation of these presynaptic receptors migh
t be involved in the death of striatal neurons in Huntington's disease, Acc
ordingly, recent findings demonstrated that the variance in the age of onse
t of Huntington's disease could be attributed to the genotype variation of
kainate receptor subunit GluR6 in humans.(24) (C) 1999 IBRO. Published by E
lsevier Science Ltd.