Expression of AMPA receptors in rat superior colliculus and effect of orbital enucleation

We analyzed the distribution and the morphological characteristics of neuro ns expressing AMPA-type glutamate receptor subunits (GluR1 and GluR2) in th e superficial partition (stratum zonale (SZ), stratum griseum superficiale (SGS) and stratum opticum (SO)) of the rat superior colliculus. GluR1-expre ssing neurons had round or ovoid somata in SGS and round or fusiform somata and primary dendrites extending tangential or horizontal side in SO. On th e other hand, GluR2-expressing neurons mainly corresponded to vertical fusi form cells with vertically oriented dendrites in SGS and medium-sized stell ate or ovoid cells with many primary dendrites in SO. The results suggest t hat the expressions of GluR1 and GluR7, are differentially regulated in ind ividual neurons of the superficial partition. To analyze the effect of reti nal deafferentation on the expression of the GluRs, we performed unilateral orbital enucleations in rats within a week after birth, Thirty days after retinal lesioning, lower expression of GluR2 mRNA was observed in the neuro ns of the contralateral side as compared with that of the ipsilateral side in SO, but not in SGS. These results indicate that GluR2 expression in the SO neurons is regulated by the correct afferentation from the retina. (C) 2 000 Elsevier Science B.V. All rights reserved.