gamma-Aminobutyric acid: a neurotransmitter candidate for cone horizontal cells of the catfish retina.
In the catfish retina, horizontal cells that receive inputs exclusively from red-sensitive cones are the only neurons that accumulate exogenous gamma-aminobutyric acid under our experimental conditions. When isolated eyecups are perfused with bicuculline methochloride, an antagonist of postsynaptic gamma-aminobutyric acid receptors, responses of cone photoreceptors to a field of light (3 mm in diameter) become much slower and approach those to a small spot of light (0.3 mm). In addition, bicuculline methochloride decreases the frequency responses of cone horizontal cells to a field of light. These findings indicate that, in the catfish retina, feedback synapses from cone horizontal cells to cones are chemically mediated and may use gamma-aminobutyric acid as a neurotransmitter. Our results also confirm the hypothesis that, in the catfish retina, a function of the negative feedback is to improve the frequency responses of the system.
D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D001640:Bicuculline / Q000494:pharmacology; D005399:Fishes / Q000502:physiology*; D018756:GABA Antagonists; D007395:Interneurons / Q000378:metabolism; D008027:Light; D018377:Neurotransmitter Agents / Q000378:metabolism*; D010786:Photoreceptor Cells / Q000502:physiology; D012160:Retina / Q000378:metabolism*; D005680:gamma-Aminobutyric Acid / Q000378:metabolism*
D018756:GABA Antagonists; D018377:Neurotransmitter Agents; D005680:gamma-Aminobutyric Acid; D001640:Bicuculline