Effects of vasoactive intestinal peptide on ganglion cells in the rabbit retina

The effects of vasoactive intestinal peptide (VIP) on the extracellularly recorded activity of ganglion cells were studied in superfused rabbit retinas. VIP, applied to the bathing solution, significantly increased the maintained activity of both OFF-center and ON-center brisk ganglion cells. The transient, excitatory responses of these cells to flashes of light (spots or annuli centered over the receptive field) were either unaffected or moderately reduced. VIP did not affect the responses of most ON/OFF directionally selective ganglion cells to a moving light stimulus. Furthermore, maintained activity of most of these cells remained absent. Effects of VIP on the light responses of ganglion cells were pronounced in retinas that were bathed with the dopamine D1 antagonist (+)-SCH 23390. For OFF-center brisk ganglion cells, VIP brought out both the center and surround excitatory responses that were selectively reduced by (+)-SCH 23390. Similarly, VIP brought out the leading edge responses that were reduced by (+)-SCH 23390 in ON/OFF directionally selective ganglion cells to a moving light stimulus. VIP did not however reverse the effects of (+)-SCH 23390 on ON-center brisk ganglion cells. It is argued that VIP counteracts the effects of (+)-SCH 23390 on OFF-center brisk ganglion cells and ON/OFF directionally selective ganglion cells by stimulating adenylate cyclase activity in dopamine-receptive cells of the retina.