Retinal lesions induce differential changes in the expression of flip and flop isoforms of the glutamate receptor subunit GluR1 in the chick optic tectum

A sensitive RNase protection assay was employed to determine the levels of mRNA encoding the GluR1 subunit flip and flop isoforms in the chick optic t ectum and forebrain. We found that the flip GluR1 mRNA predominates in the forebrain, whereas the flop variant is more strongly expressed in the optic tectum. A temporal analysis of GluR1 variants in the embryonic and adult c hick brain revealed that the flip isoform is more highly expressed at E12 t han at P15-21, whereas mRNA levels of the flop isoform are higher at P15-21 than at E12. To study the effect of deafferentation on GluR1 expression, u nilateral retinal lesions were performed. Two days later the mRNA levels of GluR1 flip and flop variants were decreased in the deafferented tectum, es pecially for the flop isoform. However, 7 days after the lesion, the mRNA l evels of both GluR1 isoforms were increased, especially for the flip isofor m. These results reveal an important control of the retinal input upon the expression of the different GluR1 isoforms. Furthermore, they indicate a di fferential spatial and temporal regulation of the flip and flop splice vari ants, suggesting the existence of a mechanism regulating differential splic ing or possibly differential RNA stability. (C) 2000 Elsevier Science B.V. All rights reserved.