axon synapses in cone retinal bipolar cell type 8 cone bipolar cell (sensu Mus) DB6 cone bipolar cell An ON-bipolar neuron found in the retina and having connections with cone photoreceptors cells and neurons in the inner half of the inner plexiform layer. This cell has the widest dendritic field and the widest axon terminal of all retinal bipolar cells. The axon terminal is delicate and stratified through sublaminae 4 and 5 of the inner plexiform layer. sublaminar layer S4 sublaminar layer S5