Figure 8. GPR55 plays an important role during retinal projection growth and target selection in vivo. A, Photomicrographs of retinal projections in the SC of P3 gpr55+/+
and gpr55-/- mouse pups injected, at P1, in one eye with CTb. B, Photomicrographs of retinal projections in the DTN of P3 gpr55+/+
and gpr55-/-
mice C, Quantification of retinal projection development in the DTN of gpr55+/+
and gpr55-/-
; collateral projection length are expressed as mean ± SEM. D, Number of collateral axon branches decreases in gpr55-/-
compared to gpr55+/+ mice. E, Images of retinogeniculate projection patterns visualized following CTb conjugated to AlexaFluor 555 (CTb-555; red) and CTb-488 (green) injections into left and right eyes of gpr55+/+
and gpr55-/- adult mice. Merged images show all projections from both eyes to the dorsal lateral geniculate nucleus, overlaying projections are shown in yellow. F, Quantification in gpr55+/+ and gpr55-/-
adult mice of the percentage of the dLGN receiving overlapping inputs as mean ± SEM. G, Photomicrographs of retinal projections in the SC of P5 hamsters injected, at P1, in one eye with CTb and LPI or vehicle. A single injection of LPI induced aberrant projections in the ipsilateral SC. H, Photomicrographs of P5 hamster retinal projections in the DTN in the control, LPI, and CBD groups. I, Quantification of retinal projection development in the DTN; collateral projection length are expressed as mean ± SEM. J, Number of collateral axon branches in treated groups compared to the control group. LPI increased axon growth and collateral branch number, whereas CBD decreased these endpoints compared with the control. Scale bars: A, B, E, G, 200 μm; H, 100 μm. n = 8 brains per condition for P3 mice, n = 7 brains per condition for adult mice, and n = 5 brains per condition for P5 hamsters; *indicates significant change compared with the control group in C, D, F, I, and J; p = 0.0001.