Time course of striatal, pallidal and thalamic α1, α2 and β2/3 GABAA receptor subunit changes induced by unilateral 6-OHDA lesion of the nigrostriatal pathway

Immunocytochemical techniques were used to investigate the distribution and abundance of GABAA receptor subunits (α1, α2 and β2/3) in the brains of unilaterally 6-OHDA-lesioned rats. Three and 7 days after lesion, the α2-subunit was significantly more abundant in the lesion-ipsilateral striatum than in the lesion-contralateral striatum; by 4 weeks after lesion, however, no significant between-side differences were observed. Three and 7 days after lesion, the α1-subunit was significantly less abundant in the lesion-ipsilateral globus pallidus than in the lesion-contralateral side; again, this difference disappeared within 4 weeks of lesion. Similarly, α1 was initially less abundant in several relay thalamic nuclei on the lesioned side while α2 was initially more abundant in intralaminar thalamic nuclei on the lesioned side. There were no significant between-side changes for the β2/3-subunits. Comparison of non-lesioned and 6-OHDA-lesioned rats revealed significant differences in brain areas which also showed differences on comparison of the lesioned and non-lesioned sides of 6-OHDA-lesioned rats. These results suggest that there is an early adaptation to the lesion, achieved through changes in GABAA receptor abundance. That some of these changes are no longer apparent after 4 weeks is due not only to partial reversion of the changes in the lesioned side but also to compensatory changes in the non-lesioned side.