Ca(2+)-induced light adaptation in retinal ON-bipolar cells.
Retinal ON-bipolar cells possess a metabotropic glutamate receptor linked to the control of a cGMP cascade, which functions to generate high synaptic amplification of rod signals under dark-adapted conditions. We report that a major component of light adaptation of the rod visual system results from a reduction in gain in synaptic transmission from rods to ON-bipolar cells, initiated by Ca(2+)-loading when the cGMP-activated channels of the postsynaptic cell open with light. When intracellular Ca(2+)-buffering was reduced adaptation was induced in ON-bipolar cells by background light too weak to significantly desensitize rods, a property absent in OFF-bipolar cells. Desensitization of ON-bipolar cell flash responses was induced by raising intracellular free Ca2+.
Shiells
R A
RA
Department of Physiology, University College London, UK. r.shiells@ucl.ac.uk
D000221:Adaptation, Ocular / Q000187:drug effects; D000818:Animals; D002118:Calcium / Q000378:metabolism / Q000494:pharmacology; D004284:Dogfish; D066298:In Vitro Techniques; D018094:Receptors, Metabotropic Glutamate / Q000378:metabolism; D017948:Retinal Rod Photoreceptor Cells / Q000187:drug effects / Q000378:metabolism / Q000528:radiation effects*
D018094:Receptors, Metabotropic Glutamate; D002118:Calcium