In light, however, light strikes the photoreceptor which causes the photoreceptor to be inhibited (hyperpolarized) due to the activation of opsins which activate All trans-Retinal, giving energy to stimulate G-Protein coupled receptors to activate phosphodiesterase (PDE) which cleaves cGMP into 5'-GMP. In photoreceptor cells, there is an abundance of cGMP in dark conditions, keeping cGMP-gated Na channels open and so, activating PDE diminishes the supply of cGMP, reducing the number of open Na channels and thus hyperpolarizing the photoreceptor cell, causing less glutamate to be released. This causes the ON bipolar cell to lose its inhibition and become active (depolarized), while the OFF bipolar cell loses its excitation (becomes hyperpolarized) and becomes silent.[1]