title: BK channels mediate dopamine inhibition of firing in a subpopulation of core nucleus accumbens medium spiny neurons.
abstract: Dopamine, a key neurotransmitter mediating the rewarding properties of drugs of abuse, is widely believed to exert some of its effects by modulating neuronal activity of nucleus accumbens (NAcc) medium spiny neurons (MSNs). Although its effects on synaptic transmission have been well documented, its regulation of intrinsic neuronal excitability is less understood. In this study, we examined the cellular mechanisms of acute dopamine effects on core accumbens MSNs evoked firing. We found that 0.5 µM A-77636 and 10 µM quinpirole, dopamine D1 (DR1s) and D2 receptor (D2Rs) agonists, respectively, markedly inhibited MSN evoked action potentials. This effect, observed only in about 25% of all neurons, was associated with spike-timing-dependent (STDP) long-term potentiation (tLTP), but not long-term depression (tLTD). Dopamine inhibits evoked firing by compromising subthreshold depolarization, not by altering action potentials themselves. Recordings in voltage-clamp mode revealed that all MSNs expressed fast (IA), slowly inactivating delayed rectifier (Idr), and large conductance voltage- and calcium-activated potassium (BKs) channels. Although A-77636 and quinpirole enhanced IA, its selective blockade by 0.5 µM phrixotoxin-1 had no effect on evoked firing. In contrast, exposing tissue to low TEA concentrations and to 10 µM paxilline, a selective BK channel blocker, prevented D1R agonist from inhibiting MSN firing. This result indicates that dopamine inhibits MSN firing through BK channels in a subpopulation of core accumbens MSNs exclusively associated with spike-timing-dependent long-term potentiation.
authors.affiliation: University of Massachusetts Medical School, The Brudnick Neuropsychiatric Research Institute, Department of Psychiatry, 303 Belmont Street, Worcester, MA 01604.
authors.forename: Xincai
authors.initials: X
authors.lastname: Ji
authors.affiliation: University of Massachusetts Medical School, The Brudnick Neuropsychiatric Research Institute, Department of Psychiatry, 303 Belmont Street, Worcester, MA 01604. Electronic address: gilles.martin@umassmed.edu.
authors.forename: Gilles E
authors.initials: GE
authors.lastname: Martin
mesh_terms: D000200:Action Potentials / Q000187:drug effects / Q000502:physiology*; D000218:Adamantane / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D001578:Benzopyrans / Q000494:pharmacology; D004298:Dopamine / Q000378:metabolism*; D018491:Dopamine Agonists / Q000494:pharmacology; D051036:Large-Conductance Calcium-Activated Potassium Channels / Q000378:metabolism*; D017774:Long-Term Potentiation / Q000187:drug effects / Q000502:physiology; D036881:Long-Term Synaptic Depression / Q000187:drug effects / Q000502:physiology; D008297:Male; D008810:Mice, Inbred C57BL; D009433:Neural Inhibition / Q000187:drug effects / Q000502:physiology*; D009474:Neurons / Q000187:drug effects / Q000502:physiology*; D009714:Nucleus Accumbens / Q000187:drug effects / Q000502:physiology*; D018408:Patch-Clamp Techniques; D026902:Potassium Channel Blockers / Q000494:pharmacology; D019257:Quinpirole / Q000494:pharmacology; D017447:Receptors, Dopamine D1 / Q000819:agonists / Q000378:metabolism; D017448:Receptors, Dopamine D2 / Q000819:agonists / Q000378:metabolism; D013111:Spider Venoms / Q000494:pharmacology; D046509:Tissue Culture Techniques
chemical_list: D001578:Benzopyrans; D018491:Dopamine Agonists; D051036:Large-Conductance Calcium-Activated Potassium Channels; D026902:Potassium Channel Blockers; D017447:Receptors, Dopamine D1; D017448:Receptors, Dopamine D2; D013111:Spider Venoms; C493513:phrixotoxin I, Phrixotrichus auratus; C079415:A 77636; D019257:Quinpirole; D000218:Adamantane; D004298:Dopamine
keywords: BK channels; Dopamine; Mice; Nucleus accumbens; Potassium channels