title: The content and release of endogenous GABA in isolated horizontal cells of the goldfish retina.
abstract: The endogenous amino acid content of intact retinas and isolated horizontal cells was measured by high performance liquid chromatography (HPLC). In both of these preparations, the concentration of gamma-aminobutyric acid (GABA) was approximately 2 mM. The endogenous GABA of the isolated horizontal cells was specifically released upon depolarization of the cells by elevated external K+ concentrations. This K+ induced release of endogenous GABA has two components. There is a saturable, Ca2+-dependent portion which predominates with small depolarizations, and a Ca2+-independent fraction which is linearly dependent upon the membrane potential of the horizontal cells. The data presented suggest the possibility of a dual scheme for the release of GABA from goldfish horizontal cells. The first is a Ca2+-dependent, conventional synaptic release; and the second a Na+-driven, carrier mediated release, which is linearly dependent upon the cellular membrane potential and functions in the absence of extracellular Ca2+.
mesh_terms: D000596:Amino Acids / Q000378:metabolism; D000818:Animals; D002469:Cell Separation; D002851:Chromatography, High Pressure Liquid; D006054:Goldfish; D066298:In Vitro Techniques; D008274:Magnesium / Q000494:pharmacology; D015636:Magnesium Chloride; D011189:Potassium Chloride / Q000494:pharmacology; D012160:Retina / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism; D005680:gamma-Aminobutyric Acid / Q000378:metabolism*
chemical_list: D000596:Amino Acids; D015636:Magnesium Chloride; D005680:gamma-Aminobutyric Acid; D011189:Potassium Chloride; D008274:Magnesium