Anti-OPN4 polyclonal antibody

Purpose: To test the hypothesis that in young, functionally blind mice, light-dependent intraretinal ion regulation occurs via melanopsin. Methods: Postnatal day (P) 7 wild type (WT, C57B1/6) and melanopsin knockout (KO, opn4-/-, B6129) mice were light or dark adapted. Awake and freely moving animals were injected intraperitoneally (ip) with MnCl(2). Four hours later, the mice in both groups were anesthetized and studied with manganese-enhanced MRI (MEMRI) to measure the extent of intraretinal uptake of manganese and whole retinal thicknesses. Results: In control P7 mice, light exposure increased (p<0.05) retinal manganese uptake over that in dark. This difference was observed throughout most of the retina. In P7 KO mice, intraretinal manganese uptake did not differ from that in age-matched dark-adapted WT mice, and was not light-dependent. No differences in whole retinal thickness were noted between groups. Conclusions: First time evidence is presented which demonstrates intraretinal ion regulation by melanopsin in vivo.

The master circadian pacemaker in mammals resides in the hypothalamic suprachiasmatic nuclei (SCN) and is synchronized to ambient light/dark cycles (i.e., photoentrainment). Melanopsin (Opn4) and classical rod-cone photoreceptors are believed to provide all the photic input necessary for circadian photoentrainment. Although the UVA-sensitive photopigment Opn5 is known to be expressed in retinal ganglion cells, its physiological role remains unclear and a potential role for Opn5 in the photoentrainment of the master clock has not been addressed. Here we report impaired photoentrainment and phase shifting to UVA light in Opn5-null mice. However, triple-knockout mice lacking all known functional circadian photoreceptors (i.e., rods, cones, and melanopsin) failed to entrain to UVA-light/dark cycles, despite the presence of Opn5, demonstrating that Opn5 alone is not sufficient for photoentrainment of the SCN dock. Since Opn5 is involved in the regulation of the retinal circadian clock, disrupted retinal function may cause impaired circadian photoentrainment in Opn5-null mice.