Inhibitory feedback shapes bipolar cell responses in the rabbit retina.
Retinal bipolar cells can be divided into on and off types based on the polarity of their response to light. Bipolar activity is further shaped by inhibitory inputs, characterized here by the events that occur immediately after the onset of a light step: 1) in most off bipolar cells, excitatory current decreased, whereas inhibitory current increased. These currents reinforced each other, enhancing the light response. 2) In about half of the on cone bipolar cells, the excitatory current increased, whereas inhibitory current decreased, also reinforcing the light response. Both of these reinforcing interactions were mediated by glycinergic inhibition. 3) In the remaining on cone bipolar cells, excitation and inhibition both increased, but inhibition was delayed so that these cells responded transiently. 4) Finally, in rod bipolar cells, excitation and inhibition both increased so that inhibition suppressed excitation, reducing the light response at all time scales. The suppressive inhibition seen in on cone and rod bipolar cells was mediated by GABA. Thus morphologically diverse bipolar cells receive only four main types of inhibitory input, and the majority of "inhibitory" inputs actually serve to enhance excitation.
Molnar
Alyosha
A
Department of Electrical Engineering and Computer Science, University of California Berkeley, Berkeley, CA 94720, USA.
Werblin
Frank
F
D000613:Aminobutyrates / Q000494:pharmacology; D000818:Animals; D001369:Axons / Q000502:physiology; D004594:Electrophysiology; D005246:Feedback / Q000502:physiology*; D018756:GABA Antagonists / Q000494:pharmacology; D005998:Glycine / Q000502:physiology; D018684:Glycine Agents / Q000494:pharmacology; D007091:Image Processing, Computer-Assisted; D066298:In Vitro Techniques; D018408:Patch-Clamp Techniques; D010721:Phosphinic Acids / Q000494:pharmacology; D010775:Photic Stimulation; D011725:Pyridines / Q000494:pharmacology; D011817:Rabbits; D018079:Receptors, GABA / Q000187:drug effects; D012160:Retina / Q000502:physiology*; D051245:Retinal Bipolar Cells / Q000502:physiology*; D017949:Retinal Cone Photoreceptor Cells / Q000502:physiology; D017948:Retinal Rod Photoreceptor Cells / Q000502:physiology; D013331:Strychnine / Q000494:pharmacology; D005680:gamma-Aminobutyric Acid / Q000502:physiology
C101879:(1,2,5,6-tetrahydropyridin-4-yl)methylphosphinic acid; D000613:Aminobutyrates; D018756:GABA Antagonists; D018684:Glycine Agents; D010721:Phosphinic Acids; D011725:Pyridines; D018079:Receptors, GABA; D005680:gamma-Aminobutyric Acid; C012729:2-amino-4-phosphonobutyric acid; D013331:Strychnine; D005998:Glycine