- Source: AII amacrine cells
AII amacrine cells are a subtype of amacrine cells. Amacrine cells are neurons that exist in the retina of mammals to assist in interpreting photoreceptive signals.
AII amacrine cells serve the critical role of transferring light signals from rod photoreceptors to the retinal ganglion cells (which contain the axons of the optic nerve).
The AII amacrine cells are unique because they work primarily with the vertical transmission of information, meaning they connect the bipolar and ganglion cells. Other amacrine cells primarily assist with horizontal pathways, meaning they connect similar types of neurons.
The Classical Rod Pathway described the role of AII amacrine cells in the mammalian retina. This can be summarised as follows:
In scotopic conditions, if a rod photoreceptor receives light in scotopic (dark) conditions, it will hyperpolarise.
The rod photoreceptor synapses with the rod bipolar cell.
This rod bipolar cell will directly (exclusively) synapse with an AII amacrine cell in sublamina B (within the inner plexiform layer)
The AII amacrine cells becomes activated (i.e., it depolarises) when light stimulates a rod.
(Once activated, the AII amacrine cell then modulates the cone ON and OFF channels):
In sublamina B, the dendrites of the AII amacrine cell also form gap junctions with:
Other AII amacrine cells
ON-cone bipolar cells
In sublamina A, the dendrites of the AII amacrine cell usually form inhibitory glycinergic synapses onto the OFF-cone bipolar cells
The ON- and OFF- cone bipolar cells in turn contact the ON- and OFF-centre retinal ganglion cells, respectively.
Note: A small proportion of rods contact the cone bipolar cells directly.
