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KMID : 0358619930270020163
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Korean Journal of Physiology
1993 Volume.27 No. 2 p.163 ~ p.174
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Electrophysiological Analysis of GABA and Glycine Action on Neurons of the Catfish Retina
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Bai Sun-Ho
Jung Chang-Sub
Lee Sung-Jong
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Abstract
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Vertebrate retinal neurons, like brain tracts farm complex synaptic relations in the enter and inner plexiform layers which ape equivalent to the central nervous system nuclei. The effects of acid(GABA) and glycine on retinal neurons were explored to discern the mechanisms of action of neurotransmitters. Experiments were performed in the superfused retina-eyecup preparation of the channel catfish, Ictalurus punctatus, using intracellular electrophysiological techniques. The roles of GABA and glycine as inhibitory neurotransmitters are well established in the vertebrate retina. But, we found that the depolarizing action of GABA and glycine on third-order neurons in the catfish retina. GABA and glycine appeared to act on retinal ueurons based on the observations that (1) effects on photoreceptors were not observed, (2) horizontal cells were either hyperpolarized or depolarized , (3) bipolar cells were all hyperpolarized (4) amacrine and ganglion cells were either hyperpolarized or depolarized , (5) GABA and glycine may be working to suppress presynaptic inhibition. The results suggest that depolarization of third-order neurons by GABA and glycine is due to at least two mechanisms; a direct postsynaptic effect and an indirect effect. Therefore, in the catfish retina, a mechanism of presynaptic inhibition or disinhibition including the direct postsynaptic effect may exist in the third-order neurons.
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KEYWORD
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Catfish retinal neurons, Eyecup, GABA, Glycine, Disinhibition
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