Wild-type mice (WT, C57BL/6J) or rats (Sprague Dawley) of both sexes and pregnant female mice were purchased from Charles River Laboratories (Wilmington, MA).
Gnao1−/− (gene encoding Gα
o1),
Grm6-GFP (GFP driven under mGluR6 promoter), and
Gnb3−/− (gene encoding Gβ
3) mice were generated and maintained as described previously.
13,24,28 The
Gng13−/− (gene encoding Gγ
13) mice were generated by the University of Pennsylvania Transgenic and Chimeric Mouse Facility, and will be described elsewhere (Ramakrishnan H, Dhingra A, Fina M, Lyubarsky A, Vardi N, manuscript in preparation, 2014). The
Grm6−/− (gene encoding mGluR6) mouse
9,10 was a gift from Shigetada Nakanishi (Kyoto University, Kyoto, Japan) and David Copenhagen (University of California, San Francisco, CA).
Trpm1−/− (gene encoding TRPM1) retinas were obtained from Neal Peachey (Cleveland Clinic, Cleveland, OH). For developmental studies, WT retinas were harvested from litters born to six different mothers at the following postnatal (P) ages: litter 1: P0, P1, P2, P4, P17, P19, P21, P25, and P28; litter 2: P0, P3, P5, P6, P7, P8, and P9; litter 3: P11 and P14; litters 4 and 5 each: P9, P11, P13, P15, P17, and P28; and litter 6: P13, P14, P15, and P19. Two additional mice were euthanized at postnatal day P21 to increase the sample number at this age. Animal care and use was in compliance with the guidelines of the Association for Research in Vision and Ophthalmology (ARVO) and Institutional Animal Care and Use Committee (IACUC) of the University of Pennsylvania. The protocol was approved by the Committee for Ethics of Animal Experiments of the University of Pennsylvania (Protocol Number 803174). Mice older than P5 were anesthetized with a mixture of ketamine (100 μg/g) and xylazine (10 μg/g), and pups younger than P5 were decapitated. Eyes were enucleated, and the cornea and lens were removed. Animals older than P5 were euthanized with an overdose (3-fold higher concentration) of the anesthetic drugs.