Final answer:
In a dark environment, the membrane of bipolar cells is depolarized, leading to the greatest release of neurotransmitters.
Step-by-step explanation:
When light strikes rhodopsin, the G-protein transducin is activated, which in turn activates phosphodiesterase. Phosphodiesterase converts CGMP to GMP, thereby closing sodium channels. As a result, the membrane becomes hyperpolarized. The hyperpolarized membrane does not release glutamate to the bipolar cell. Therefore, a dark environment, where light is absent, will depolarize the membrane and result in the release of neurotransmitters (NT) from bipolar cells, leading to the greatest release of NT from Bipolars.