Inhibitory network properties shaping the light evoked responses of cat alpha retinal ganglion cells.
Cat retinal ganglion cells of the Y (or alpha) type respond to luminance changes opposite those preferred by their receptive-field centers with a transient hyperpolarization. Here, we examine the spatial organization and synaptic basis of this light response by means of whole-cell current-clamp recordings made in vitro. The hyperpolarization was largest when stimulus spots approximated the size of the receptive-field center, and diminished substantially for larger spots. The hyperpolarization was largely abolished by bath application of strychnine, a blocker of glycinergic inhibition. Picrotoxin, an antagonist of ionotropic GABA receptors, greatly reduced the attenuation of the hyperpolarizing response for large spots. The data are consistent with a model in which (1) the hyperpolarization reflects inhibition by glycinergic amacrine cells of bipolar terminals presynaptic to the alpha cells, and perhaps direct inhibition of the alpha cell as well; and (2) the attenuation of the hyperpolarization by large spots reflects surround inhibition of the glycinergic amacrine by GABAergic amacrine cells. This circuitry may moderate nonlinearities in the alpha-cell light response and could account for some excitatory and inhibitory influences on alpha cells known to arise from outside the classical receptive field.
O'Brien
Brendan J
BJ
Department of Neuroscience, Brown University, Box 1953, Providence, RI 02912-1953, USA.
Richardson
Randal C
RC
Berson
David M
DM
D025042:Amacrine Cells / Q000502:physiology; D000818:Animals; D002415:Cats; D004594:Electrophysiology; D005998:Glycine / Q000502:physiology; D066298:In Vitro Techniques; D008027:Light; D009415:Nerve Net / Q000502:physiology*; D009433:Neural Inhibition / Q000502:physiology*; D010775:Photic Stimulation / Q000379:methods; D012165:Retinal Ganglion Cells / Q000502:physiology* / Q000528:radiation effects*; D009435:Synaptic Transmission; D005680:gamma-Aminobutyric Acid / Q000502:physiology
D005680:gamma-Aminobutyric Acid; D005998:Glycine