The TRPM subfamily of mammalian TRP channels includes TRPM1, which is required for the photoresponse in retinal ON-bipolar cells []. In conditions of darkness, glutamate is released from photoreceptors, activating the metabotropic glutamate receptor 6 on retinal ON bipolar cells. This activates the G protein G(o), which then closes TRPM1 channels, leading to hyperpolarisation of the cells []. Mutations in TRPM1 can cause congenital stationary night blindness [, ].
