title: Dopamine inhibits calcium-independent gamma-[3H]aminobutyric acid release induced by kainate and high K+ in the fish retina.
abstract: Kainic acid (KA) at micromolar concentrations stimulated the release of gamma-[3H]aminobutyric acid [( 3H]GABA) from a particulate fraction of the carp (Cyprinus carpio) retina. The KA action was dose-dependent but Ca2+-independent. A similar response was elicited by another glutamate receptor agonist, quisqualic acid, and high K+, but not by an aspartate agonist, N-methyl-D-aspartic acid. The stimulatory action of KA on the [3H]GABA release was selectively blocked by the KA blockers gamma-D-glutamylglycine and cis-2,3-piperidine dicarboxylic acid. Dopamine (DA), which is contained in DA interplexiform cells in the carp retina, inhibited the [3H]GABA release induced by KA and high K+ in a dose-dependent manner. 5-Hydroxytryptamine and two well-known GABA antagonists, bicuculline (Bic) and picrotoxin (Pic), also mimicked the DA effect on the GABA release at a comparable concentration. This inhibitory effect of DA as well as Bic and Pic on the [3H]GABA release evoked by KA was clearly antagonized by a DA blocker, haloperidol. The action of these agents (KA, DA, GABA antagonist) belonging to three different receptor categories on the GABAergic neurons (possibly external horizontal cells; H1 cells) is discussed in relation to other electrophysiological studies on the lateral spread of S-potentials between H1 cells.
mesh_terms: D000818:Animals; D001224:Aspartic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D001640:Bicuculline / Q000494:pharmacology; D002118:Calcium / Q000494:pharmacology*; D004298:Dopamine / Q000494:pharmacology*; D005399:Fishes; D006220:Haloperidol / Q000494:pharmacology; D007608:Kainic Acid / Q000494:pharmacology*; D016202:N-Methylaspartate; D010069:Oxadiazoles / Q000494:pharmacology; D010852:Picrotoxin / Q000494:pharmacology; D011188:Potassium / Q000494:pharmacology*; D011759:Pyrrolidines / Q000494:pharmacology*; D016318:Quisqualic Acid; D012160:Retina / Q000187:drug effects* / Q000378:metabolism; D012701:Serotonin / Q000494:pharmacology; D005680:gamma-Aminobutyric Acid / Q000378:metabolism*
chemical_list: D001224:Aspartic Acid; D001640:Bicuculline; D002118:Calcium; D004298:Dopamine; D006220:Haloperidol; D007608:Kainic Acid; D016202:N-Methylaspartate; D010069:Oxadiazoles; D010852:Picrotoxin; D011188:Potassium; D011759:Pyrrolidines; D016318:Quisqualic Acid; D012701:Serotonin; D005680:gamma-Aminobutyric Acid