Application of transretinal current stimulation for the study of bipolar-amacrine transmission.
Transretinal current flowing from the receptor side to the vitreous side depolarizes the axon terminals of retinal cells and facilitates the release of transmitter. Such current elicited a depolarizing response in off-center bipolar cells and a hyperpolarizing response in on-center bipolar cells. It also elicited a response of relatively complex waveform in amacrine cells. The responses elicited in bipolar cells were suppressed in the presence of 5-10 mM glutamate in the perfusing Ringer solution, while the responses of amacrine cells persisted, although their waveform changed to a simple one that showed monotonic depolarization irrespective of the type of amacrine cell and were accompanied by a decrease in the membrane resistance. The results indicate excitatory synaptic transmission from bipolar cells to amacrine cells. Since the response elicited by current in ON-OFF cells was almost identical to those elicited in ON or OFF amacrine cells, the transient nature of their light response cannot be due to their membrane properties. ON-OFF cells responded to transretinal current flowing in the opposite direction with a small hyperpolarization accompanied by a resistance increase. The hyperpolarizing response was suppressed by the addition of GABA in glutamate Ringer solution. The results suggest an activation by the current of GABA-ergic feedback pathways from amacrine cells to bipolar cells.
D000818:Animals; D002347:Carps; D004558:Electric Stimulation; D005071:Evoked Potentials / Q000187:drug effects; D005971:Glutamates / Q000494:pharmacology; D018698:Glutamic Acid; D008564:Membrane Potentials / Q000187:drug effects; D008839:Microelectrodes; D009474:Neurons / Q000502:physiology*; D010775:Photic Stimulation; D010786:Photoreceptor Cells / Q000502:physiology; D012160:Retina / Q000502:physiology*; D013569:Synapses / Q000502:physiology; D009435:Synaptic Transmission / Q000187:drug effects
D005971:Glutamates; D018698:Glutamic Acid