How do OFF bipolar cells respond to glutamate?
Because glutamate release is decreased upon exposure to light, a bipolar cell that responds to glutamate by excitation will be excited when the light is off. These are called off-center bipolar cells because they are active when the light is off in the center of their receptive field (Figure 4.8. 8).
What does glutamate do to bipolar cells?
In the dark, a photoreceptor (rod/cone) cell will release glutamate, which inhibits (hyperpolarizes) the ON bipolar cells and excites (depolarizes) the OFF bipolar cells.
Do bipolar cells release glutamate?
The neurotransmitter released by the bipolar cell is glutamate. The neurotransmitter released by the amacrine cell is GABA. When the bipolar cell depolarizes, it releases more glutamate onto the terminal of the amacrine cell.
Do bipolar cells release GABA?
Bipolar cells express different GABA receptors in their dendrites and axon terminals. (A) Ionic current induced by 200 ms pressure application of 30 μM GABA from a puff pipette with a fine tip located in the near proximity (ca.
What stimulates bipolar cells?
Light responses in bipolar cells are initiated by synapses with photoreceptors. Photoreceptors release only one neurotransmitter, glutamate (21); yet bipolar cells react to this stimulus with two different responses, ON-center (glutamate hyperpolarization) and OFF-center (glutamate depolarization).
How does an off bipolar cell differ from an on bipolar cell?
ON-center bipolar cells are depolarized by small spot stimuli positioned in the receptive field center. OFF-center bipolar cells are hyperpolarized by the same stimuli. Both types are repolarized by light stimulation of the peripheral receptive field outside the center (Fig. 1).
Why do bipolar on cells depolarize to light?
Photoreceptors hyperpolarize in response to light and reduce the rate of glutamate release, which in turn causes the depolarization of ON-bipolar cells. This ON-bipolar cell response is mediated by the metabotropic glutamate receptor, mGluR6, which controls the activity of a depolarizing current.
Are bipolar cells hyperpolarized?
How do the ON bipolar cells become active in response to illumination?
Cells belonging to the ON channel are depolarized by the onset of light, while members of the OFF channel depolarize when light is turned off. Instead, all photoreceptor are hyperpolarized by light, and channels are created by differential expression of glutamate receptors on the dendrites of bipolar cells.
How are bipolar cells activated?
What does glutamate do in the eye?
Glutamate is the neurotransmitter of the neurons of the vertical pathways through the retina. All photoreceptor types, rods and cones, use the excitatory amino acid glutamate to transmit signals to the next order neuron in the chain (See chapter on glutamate and Massey, 1990, for review).