Centrifugal fibres synapse on dopaminergic interplexiform cells in the teleost retina.

In teleost fish, centrifugal fibres originating in the olfactory bulb and containing FMRFamide-like and luteinizing hormone releasing hormone (LHRH)-like peptides project to the retina and terminate along the border of the inner nuclear and inner plexiform layers. Using a novel simultaneous two-colour immunolabelling technique, we have found that these centrifugal fibres are often closely apposed to the dopaminergic interplexiform cells. Contacts between centrifugal fibres and dopaminergic interplexiform cells were observed by electron microscopy to be conventional type synaptic junctions. Since the dopaminergic interplexiform cells make synapses on horizontal and bipolar cells, providing an intraretinal centrifugal pathway for information flow from the inner to the outer plexiform layers, we conclude that every neuron in the teleost retina is potentially susceptible to central influences via these centrifugal fibres and dopaminergic interplexiform cells.