title: Amoxapine inhibits delayed outward rectifier K(+) currents in cerebellar granule cells via dopamine receptor and protein kinase A activation.
abstract: BACKGROUND
  Although tricyclic antidepressants amoxapine is proposed to target 5-HT and D2 receptors, very few studies have addressed the effect of amoxapine on molecular and cellular mechanisms via receptor pathways. In this study, we test the effect of amoxapine on rat cerebellar granule neurons (CGNs) to address this possibility.
  
  
  METHODS
  CGNs cell culture, whole-cell current recording using a patch-clamp technique, western blot and non-radioactive detection analysis of phosphorylated protein kinase A (PKA) were used.
  
  
  RESULTS
  Amoxapine inhibits delayed rectifier potassium (I(K)) current in a dose-dependent manner and modulates inactivation properties in CGNs. Those effects were not eliminated by preincubation with 5-HT or 5-HT receptor antagonists, but abolished by dopamine and D1/D5 receptor antagonists. Application of GTPγ-S and inhibitor of the Gs signalling cascade abolished the amoxapine-induced effect on I(K). The application of forskolin or dibutyryl-cAMP mimicked the inhibitory effect of amoxapine on I(K). Western blotting for phosphorylated PKA revealed that amoxapine significantly increased the intracellular levels of phosphorylated PKA, a marker of PKA activation.
  
  
  CONCLUSIONS
  Amoxapine inhibits I(K) currents in rat CGNs via cAMP/PKA-dependent pathways, as in mouse cortical neurons we reported earlier, but that involves D1-like receptors instead of 5-HT receptors.
authors.affiliation: Institutes of Brain Science, School of Life Sciences and State Key Laboratory of Medical Neurobiology, Fudan University, Shanghai, PR China.
authors.forename: Guang
authors.initials: G
authors.lastname: Yang
authors.forename: Meng-Hua
authors.initials: MH
authors.lastname: Zhou
authors.forename: Zhen
authors.initials: Z
authors.lastname: Ren
authors.forename: Jia-Jie
authors.initials: JJ
authors.lastname: Xu
authors.forename: Yan-Ai
authors.initials: YA
authors.lastname: Mei
mesh_terms: D000657:Amoxapine / Q000494:pharmacology*; D000818:Animals; D002478:Cells, Cultured; D002531:Cerebellum / Q000166:cytology / Q000378:metabolism*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000737:chemistry / Q000378:metabolism*; D018492:Dopamine Antagonists / Q000494:pharmacology*; D004789:Enzyme Activation; D019205:GTP-Binding Protein alpha Subunits, Gs / Q000378:metabolism; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D024661:Potassium Channels, Inwardly Rectifying / Q000037:antagonists & inhibitors* / Q000378:metabolism / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D011954:Receptors, Dopamine / Q000737:chemistry / Q000378:metabolism*; D012702:Serotonin Antagonists / Q000494:pharmacology; D015398:Signal Transduction
chemical_list: D018492:Dopamine Antagonists; D024661:Potassium Channels, Inwardly Rectifying; D011954:Receptors, Dopamine; D012702:Serotonin Antagonists; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D017868:Cyclic AMP-Dependent Protein Kinases; D019205:GTP-Binding Protein alpha Subunits, Gs; D000657:Amoxapine