Are OFF-center bipolar cells excited or inhibited by glutamate?

OFF-center bipolar cells are specifically designed to respond to decreases in light. When light is present and activates photoreceptors, these receptors release glutamate. In the ON pathway, glutamate has an excitatory effect on ON-center bipolar cells, but a different reaction occurs with OFF-center bipolar cells. When glutamate binds to the receptors on OFF-center bipolar cells, it inhibits them. This means that in bright conditions where photoreceptors are activated, the OFF-center bipolar cells are not excited but rather inhibited, resulting in less neurotransmitter release to ganglion cells.

Hence, the correct interpretation reflects that OFF-center bipolar cells are inhibited by glutamate, leading to a reduction in their activity in response to light. This inhibition is necessary for the OFF-center bipolar cells to contribute to the visual signal when there is a decrease in light stimuli, emphasizing their role in detecting edges and contrasts in the visual field.