Abstract
Abstract: :
Purpose: The experimental aim was to correlate the GABA and glycine receptor physiology with the presence of specific receptors on the dendrites of α-ganglion cells in the rabbit retina. Methods: Whole-cell patch-clamp recordings were obtained from α-ganglion cells in the in vitro retina eyecup preparation that was superfused with a Ringer’s solution containing 2 mM cobalt to synaptically isolate the cells. GABA and glycine were pressure applied through a glass pipette positioned near the soma while antagonists were superfused. Sulforhodamine B was used to label the cells during the whole-cell recordings in order to correlate the cell’s immunocytochemistry with its physiology. Specific receptor types were localized on the labeled cell with primary antibodies directed against specific receptor peptides. Confocal microscopy was used to visualize fluorescent receptor complexes in retinal wholemounts. Results: Physiological results indicated that the dendrites of synaptically isolated cells contain: 1. GABAA receptors that were blocked by their specific antagonist, bicuculline; 2. GABAC receptors that were blocked by their specific antagonist, TPMPA; and 3. GABAB receptors that were activated by their specific agonist, baclofen. Glycine always evoked a current that was antagonized by strychnine. Without exception, all the off-cells examined exhibited larger glycine- than GABA-activated currents. On the other hand, on-cells fell into two groups, one with larger glycine- than GABA-activated currents and the other with much larger GABA- than glycine-activated currents. Sulforhodamine B-labeled cells were immunoreacted with antibodies directed against either the GABAA, GABAB, or glycine receptor. Optical sections displayed fluorescing puncta that effectively localized all three receptor types to labeled somata and dendrites of α-ganglion cells in the rabbit retina. Conclusion: Alpha ganglion cells in the rabbit retina express all three GABA receptor subtypes and a single type of strychnine-sensitive glycine receptor. Physiological and immunocytochemical evidence support these findings.
Keywords: 415 ganglion cells • 440 inhibitory receptors • 559 retinal connections, networks, circuitry