Metabotropic glutamate receptor mGluR2/3 immunoreactivity in the mouse superior colliculus: Co-localization with calbindin D28K

WE have studied the distribution of mGluR2/3 in the mouse superior colliculus (SC) with antibody immunocytochemistry and the effect of enucleation on this distribution. We also compared this labeling to that for calbindin D28K. Anti-mGluR2/3-immunoreactive (IR) cells formed distinctive laminar patterns within the lower optic and upper intermediate gray layers. By contrast, anti-calbindin D28K-IR cells formed obvious laminar patterns in three layers: one within the zonal and upper superficial gray layers, a second within the optic and intermediate gray layers, and the third within the deep gray layer. The distribution of mGluR2/3-IR cells thus matches the second layer of calbindin D28K cells. Two-color immunofluorescence revealed that more than half (52.5%) of mGluR2/3-IR cells were also labeled with antibody to calbindin D28K. The majority of mGluR2/3-IR cells were small to medium-sized round/oval or stellate cells. Immunoreactivity for mGluR2/3 was clearly reduced in the contralateral SC following unilateral enucleation. The present results show that mGluR2/3 has a unique cellular sublaminar organization in SC that includes some calbindin D28KIR cells. The effects of enucleation suggest that the retinal projection may control the expression of mGluR2/3 in some cells in the mouse SC.