Are OFF-center bipolar cells depolarized or hyperpolarized in the dark?

In the dark, OFF-center bipolar cells are depolarized, which is pivotal for their function in the visual system. These cells are critically involved in the processing of visual information, particularly in responding to decreases in light levels.

When light is absent, the photoreceptor cells (rods and cones) in the retina are in a state of darkness and continuously release glutamate. OFF-center bipolar cells express ionotropic glutamate receptors that mediate this response. When glutamate binds to these receptors in the dark, it causes the bipolar cells to depolarize. This depolarization leads to an increase in the release of neurotransmitters from the bipolar cells onto the ganglion cells, which then sends visual information to the brain.

This process allows OFF-center bipolar cells to signal changes in light conditions effectively. Thus, the depolarization of these cells in the dark is crucial as it plays a role in how we perceive contrast and movement when transitioning from light to dark environments.