title: GABAergic inhibition on dopamine cells of the fish retina: a [3H]dopamine release study with isolated fractions.
abstract: Inner retinal cells including dopamine (DA) cells were isolated and fractionated from the carp (Cyprinus carpio) retina by an enzyme cell dissociation and metrizamide gradient centrifugation method. When gamma-aminobutyric acid (GABA) antagonists (bicuculline and picrotoxin) were added into the perfusate over such a cell fraction, they stimulated the release of [3H]DA which had been preloaded in the cell fraction. The action of GABA antagonists was dose and Ca2+ dependent. Their minimal effective concentration was very low (0.5 microM). A similar action was elicited by high K+. In the presence of excess GABA, this stimulatory action of GABA antagonists and high K+ on [3H]DA release was completely abolished. To interpret the action of GABA antagonists on DA cells, isolated cell fractions were preincubated with GABAse. After such a treatment, the stimulatory effects of GABA antagonists and high K+ on [3H]DA release were differentiated from each other; the former disappeared whereas the latter remained unchanged. The data strongly suggest that GABA inhibits the DA release from retinal DA cells and thus the GABA antagonists affect [3H]DA release from cell fractions not by a direct membrane action but by a disinhibition mechanism via GABA receptors on the DA cell bodies.
authors.affiliation: Department of Neurophysiology, University of Kanazawa School of Medicine, Japan.
authors.forename: S
authors.initials: S
authors.lastname: Ishita
authors.forename: K
authors.initials: K
authors.lastname: Negishi
authors.forename: T
authors.initials: T
authors.lastname: Teranishi
authors.forename: Y
authors.initials: Y
authors.lastname: Shimada
authors.forename: S
authors.initials: S
authors.lastname: Kato
mesh_terms: D000612:4-Aminobutyrate Transaminase / Q000494:pharmacology; D000445:Aldehyde Oxidoreductases / Q000494:pharmacology; D000818:Animals; D001640:Bicuculline / Q000494:pharmacology; D002118:Calcium / Q000494:pharmacology; D002347:Carps / Q000378:metabolism*; D003530:Cyprinidae / Q000378:metabolism*; D004298:Dopamine / Q000378:metabolism*; D018756:GABA Antagonists; D007150:Immunohistochemistry; D010852:Picrotoxin / Q000494:pharmacology; D011188:Potassium / Q000494:pharmacology; D012160:Retina / Q000187:drug effects / Q000378:metabolism*; D005680:gamma-Aminobutyric Acid / Q000502:physiology*
chemical_list: D000612:4-Aminobutyrate Transaminase; D000445:Aldehyde Oxidoreductases; D001640:Bicuculline; D002118:Calcium; D004298:Dopamine; D018756:GABA Antagonists; D010852:Picrotoxin; D011188:Potassium; D005680:gamma-Aminobutyric Acid; C046738:gabase