| Preferential Suppression of the On Pathway by r-Aminobutyric Acid in the Catfish Retina. |
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Sun Ryang Bai, Chang Sub Jung, Sung Jong Lee, So Yeon Lee, Sun Ho Bai |
1Department of Ophthalmology, Catholic University Medical College, Seoul, Korea.
2Department of Physics, Catholic University, Seoul, Korea. |
| 메기 망막의 ON 경로에 대한 r-aminobutyric acid 의 선별적 억제작용 |
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배선량(Sun Ryang Bai),정창섭(Chang Sub Jung),이성종(Sung Jong Lee),이소연(So Yeon Lee),배선호(Sun Ho Bai) |
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| Abstract |
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The effects of r-aminobutyric acid(GABA) agonsits and antagonists were explored by the intracellular recording method to discern the preferential suppression of the ON component by GABA on the ON-OFF transient cell in the catfish (Ictalurus punctatus) retina. Experiments were performed in the superfused eyecup preparation. The animals were decapitated and pited before the eye, and the surrounding tissue was removed from the skull. The retina was exposed by excising the cornea, iris, and vitreous. This preparation rested on a wad of Ringer`s soaked cotton in contact with an Ag/Agcl reference electrode. Solutions were delivered through a manifold system that was connected to a pipette located near the absorbent wick. Electro-physiological recordings were made using standard intracellular electrodes filled with 2 M potassium acetate. The electrical signal was recorded with an amplifierand a penwriter, viewed on an oscilloscope, and stored on a data recorder. The light sources were red light-emitting-diode (LED) and the stimuli were full field illumination covering the cntire retina. GABA preferentially reduced ON light responses in ON-OFF transient cell. and GABA hyperpolarized bipolar cells, but the effects on ON bipolar cells were more sensitive than OFF bipolar cells. CACA and TACA, GABAc receptor agonist, did not act on bipolar cells. CACA and TACA, GABAc receptor agonists, hyperpolarized bipolar cells but the sensitivity deferences between ON and OFF bipolar cell were not observed. These results suggest that the preferential suppression of the ON component of the ON-OFF transient cell by GABA was resulted from the presynaptic mechanism that reduced bipolar cell input. |
| Key Words:
Intracellular recording;CACA GABA;Catfish retinal neurons |
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