Haloperidol suppresses light-induced spinule formation and biphasic responses of horizontal cells in fish (roach) retina.
In retinae of lower vertebrates, negative feed-back interactions between horizontal cells (second-order neurones), and cone photoreceptors lead to generation of spectrally multi-phasic light-evoked responses (S-potentials) in horizontal cells. Spinules (finger-like extensions of horizontal cell dendrites) have been suggested to mediate these interactions in retinae of teleost fish. We have studied whether prevention of light-dependent spinule formation would indeed affect an S-potential component (the red-sensitive depolarization in H2 horizontal cells), known to depend on such negative feed-back. Haloperidol was used as a dopamine antagonist to suppress light-induced formation of spinules in retinae of the cyprinid fish, the roach. In normal (untreated) retinae, biphasic S-potentials were strongly depolarizing and horizontal cell dendrites possessed abundant spinules. However, following application of haloperidol to the vitreous prior to light adaptation, spinule formation was suppressed, and concomitantly, red-sensitive depolarizing S-potentials remained significantly under-developed. The results are consistent, therefore, with the idea that spinules mediate the negative feed-back interaction between horizontal cells and cones.
Djamgoz
M B
MB
Department of Pure and Applied Biology, Imperial College of Science, Technology and Medicine, London, U.K.
Kirsch
M
M
Wagner
H J
HJ
D000818:Animals; D003530:Cyprinidae / Q000502:physiology*; D004298:Dopamine / Q000378:metabolism / Q000502:physiology*; D018492:Dopamine Antagonists; D006220:Haloperidol / Q000494:pharmacology*; D008564:Membrane Potentials / Q000187:drug effects; D010775:Photic Stimulation; D012160:Retina / Q000187:drug effects / Q000502:physiology*
D018492:Dopamine Antagonists; D006220:Haloperidol; D004298:Dopamine