title: Galantamine inhibits slowly inactivating K+ currents with a dual dose-response relationship in differentiated N1E-115 cells and in CA1 neurones.
abstract: Galantamine, one of the major drugs used in Alzheimer's disease therapy, is a relatively weak acetylcholinesterase inhibitor and an allosteric potentiating ligand of nicotinic acetylcholine receptors. However, a role in the control of excitability has also been attributed to galantamine via modulation of K+ currents in central neurones. To further investigate the effect of galantamine on voltage-activated K+ currents, we performed whole-cell voltage-clamp recordings in differentiated neuroblastoma N1E-115 cells and in dissociated rat CA1 neurones. In both cell models, one can identify two main voltage-activated K+ current components: a relatively fast inactivating component (Ifast; time constant approximately hundred milliseconds) and a slowly inactivating one (Islow; time constant approximately 1 s). We show that galantamine (1 pM-300 microM) inhibits selectively Islow, exhibiting a dual dose-response relationship, in both differentiated N1E-115 cells and CA1 neurones. We also demonstrate that, in contrast with what was previously reported, galantamine-induced inhibition is not due to a shift on the steady-state inactivation and activation curves. Additionally, we characterized a methodological artefact that affects voltage-dependence as a function of time in whole-cell configuration, observed in both cell models. By resolving an inhibitory role on K+ currents in a non-central neuronal system and in hippocampal neurones, we are attributing a widespread role of galantamine on the modulation of cell excitability. The present results are relevant in the clinical context, since the effects at low dosages suggest that galantamine-induced K+ current inhibition may contribute to the efficiency of galantamine in the treatment of Alzheimer's disease.
authors.affiliation: Faculdade de Ciências Médicas, Universidade Nova de Lisboa, Campo Mártires da Pátria, 130, 1169-056 Lisboa, Portugal.
authors.forename: M Inês
authors.initials: MI
authors.lastname: Vicente
authors.forename: Pedro F
authors.initials: PF
authors.lastname: Costa
authors.forename: Pedro A
authors.initials: PA
authors.lastname: Lima
mesh_terms: D000200:Action Potentials / Q000187:drug effects* / Q000502:physiology; D000818:Animals; D056547:CA1 Region, Hippocampal / Q000187:drug effects* / Q000502:physiology; D002454:Cell Differentiation / Q000187:drug effects* / Q000502:physiology; D045744:Cell Line, Tumor; D004305:Dose-Response Relationship, Drug; D005702:Galantamine / Q000008:administration & dosage*; D051379:Mice; D009474:Neurons / Q000166:cytology / Q000187:drug effects* / Q000502:physiology; D026902:Potassium Channel Blockers / Q000008:administration & dosage*; D015221:Potassium Channels / Q000502:physiology; D051381:Rats
chemical_list: D026902:Potassium Channel Blockers; D015221:Potassium Channels; D005702:Galantamine