Striatal ionotropic glutamate receptor ontogeny in the rat

Rat striatal N-methyl-D-aspartate (NMDA), alpha-amino-3-hydroxy-5-methyl-4- isoxazole propionic acid (AMPA) and kainate (KA) receptor staining were eva luated postnatally in the rat. Immunohistochemistry was used to detect subu nit proteins of the three glutamate receptor subtypes. The glutamate recept ors displayed distinct developmental expression patterns in the striatum. M orphological distributions for the NMDA R1 subunit (representative of NMDA receptors), Glu R1 and Glu R2/3 subunits (indicative of AMPA receptors), an d Glu R5/6/7 subunits (demonstrating KA receptors) attained adult expressio n patterns and levels at different postnatal time points. The ontogenic mat uration sequence of striatal glutamate receptor expression was KA, then AMP A and lastly NMDA. Staining patterns for NMDA and AMPA subunit proteins wer e detected initially as dense patches in the neuropil, which changed to a h omogeneous stain of the striatum by the second week of life. Cellular stain ing for the three subtypes was intense within the highly reactive neuropil patches, but less intensely stained in neurons located outside these zones. The KA receptor subunit did not exhibit neuropil heterogeneity, but was di stributed evenly at birth. All three glutamate receptor subtypes were visib le within the striatal neuron populations. Populations of striatal neurons that expressed the three differential glutamate receptor subtypes overlap, exhibit different growth patterns and dendritic staining. These results sup port a functional emergence of different glutamate receptor activation with in the striatum and provide a potential therapeutic means to isolate develo pmental disorders specifically associated with excitatory circuits of the b asal ganglia. Copyright (C) 2000 S. Karger AG, Basel.