Figure 2. Temporal pattern of MT₂ mRNA expression and cellular distribution of MT₂ receptor in ciliary processes of C57BL/6J versus DBA/2J mice. A: Total RNA from the ciliary processes of either control (C57BL/6J) or glaucomatous (DBA/2J) animals at 3, 6, 9, or 12 months of age was extracted, and MT2 mRNA was quantified with quantitative real-time PCR (qPCR) as described in the Methods section. Values were normalized to the content of the glyceraldehyde-3-phosphate dehydrogenase (GAPDH) transcript. Results are the mean ± standard error of the mean (SEM) of 24 animals of each strain (***p<0.001 versus the same mouse strain; ^#p<0.05, ^###p<0.001 versus a different mouse strain; one-way analysis of variance (ANOVA) with Dunnett’s multiple comparisons test). B: Immunofluorescence images of ciliary processes from 3-month-old C57BL/6J (I), 3-month-old DBA/2J (II), and 12-month-old DBA/2J (III) mice labeled with antibodies against the MT₂ receptor (green). Nuclei were counterstained with propidium iodide (red). Phase-contrast and confocal images show that the MT₂ receptor is mainly located in the non-pigmented epithelium of the ciliary processes, and expression of the receptor is strongly increased in the 3-month-old DBA/2J mice compared to the older mice and to the 3-month-old C57BL/6J mice. Scale bar = 20 μm.