Blind C3H substrains differ in anxiety-like behavior, weight gain, and circadian period but not in responses to constant light

C3H/HeJ and C3H/HeNCrl mice are both functionally blind due to the Pde6b^rd1 mutation, yet retain melanopsin-mediated circadian photoreception. We compared these substrains across circadian, behavioral, and metabolic measures under 12:12 light-dark (LD) and constant light (LL) conditions. Male and female mice were housed in LD or LL for 8 weeks, then assessed for circadian rhythms, open field activity, light-dark box preference, and physiological endpoints. Under LL, HeN mice exhibited significantly greater circadian period lengthening than HeJ mice despite both substrains lacking functional rods and cones, revealing substrain differences in melanopsin-mediated photosensitivity. Sex differences in circadian period were evident, with females showing longer periods than males in LL. HeN mice displayed increased anxiety-like behavior, reflected in reduced center zone time and increased dark zone occupancy, as well as reduced novelty-induced locomotor activity (distance traveled and velocity), compared to HeJ mice, independent of light cycle. Male HeN mice gained more weight and consumed more food than HeJ males in LD only. These circadian and behavioral differences parallel patterns observed in C57BL/6 substrains, with Charles River-derived mice exhibiting altered circadian photosensitivity and heightened anxiety relative to Jackson Laboratory mice. These findings emphasize the importance of specifying substrain origin in circadian research using C3H mice.