title: A dopaminergic inhibitory postsynaptic potential mediated by an increased potassium conductance.
abstract: Intracellular recordings from intact pituitary melanotrophs show that, in the same cell, inhibitory postsynaptic potentials resulting from either pituitary stalk stimulation or exogenous dopamine are abolished by D2 receptor antagonists, display identical conductance changes, are reversed in polarity at the same membrane potential and are sensitive to pertussis toxin pretreatment. The reversal potential of the inhibitory postsynaptic potential shows a 65 mV shift with a 10-fold change in external potassium concentration, which is close to that predicted by the Nernst equation. We conclude that activation of this synapse releases dopamine which acts on a D2 receptor to increase potassium conductance via a G-protein-mediated mechanism. This is the first characterization of an inhibitory dopaminergic synapse in the mammalian nervous system.
authors.affiliation: Neuroscience Research Group, Faculty of Medicine, University of Calgary, Alberta, Canada.
authors.forename: P J
authors.initials: PJ
authors.lastname: Williams
authors.forename: B A
authors.initials: BA
authors.lastname: MacVicar
authors.forename: Q J
authors.initials: QJ
authors.lastname: Pittman
mesh_terms: D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D001640:Bicuculline / Q000494:pharmacology; D004298:Dopamine / Q000494:pharmacology / Q000502:physiology*; D066298:In Vitro Techniques; D008564:Membrane Potentials / Q000187:drug effects; D009433:Neural Inhibition / Q000187:drug effects*; D037342:Pertussis Toxin; D010902:Pituitary Gland / Q000187:drug effects / Q000502:physiology*; D011188:Potassium / Q000502:physiology*; D051381:Rats; D011919:Rats, Inbred Strains; D013469:Sulpiride / Q000494:pharmacology; D013779:Tetrodotoxin / Q000494:pharmacology; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
chemical_list: D010566:Virulence Factors, Bordetella; D013779:Tetrodotoxin; D013469:Sulpiride; D037342:Pertussis Toxin; D011188:Potassium; D004298:Dopamine; D001640:Bicuculline