Question

Scientists have just discovered a new species of fish. They find that the photoreceptors in its eyes behave like those of other animals in every other respect with one exception: they all release the inhibitory neurotransmitter GABA. All of the bipolar cells of this animal respond to GABA the same way (with a chloride channel-mediated IPSP). Are the receptive fields of bipolar cells in this animal's eyes on- or offcenter? Briefly explain your reason.

Answer 1

Answer: Bipolar cells receive inputs from a set of photoreceptor cells, which define the bipolar cell’s receptive field. GABA (gamma-aminobutyric acid) is an inhibitory neurotransmitter. In the fish, all the photoreceptors release the inhibitory neurotransmitter GABA. In this case, there will be increased GABA efflux. This efflux can be inhibited by turning the light back on.

The receptive fields of bipolar cells in this animal’s eye is on-centre. In this case, the bipolar cells will be excited when the light is on. With a decrease in illumination, there is an increase in the release of photoreceptor transmitters.