Representative photomicrographs illustrating single DBH (green), single MEL1a (red) and colocalized DBH + MEL1a (yellow) immunostaining in the LC after 10 weeks of vehicle treatment (a-c), chronic MEL treatment (d-f) and SD photoperiod exposure (g-i). 4V, forth ventricle; LC, locus coeruleus; Me5, mesencephalic trigeminal nucleus. n = 15. Scale bar = 50 μm.