Abstract
Ion channels are known to be modulated by antidepressant drugs, but the molecular mechanisms are not known. We have shown that the antidepressant drug amoxapine suppresses rectifier outward K+ (IK) currents in mouse cortical neurons. At a concentration of 10 to 500 μM, amoxapine reversibly inhibited IK in a dose-dependent manner and modulated both steady-state activation and inactivation properties. The application of forskolin or dibutyryl cAMP mimicked the inhibitory effect of amoxapine on IK and abolished further inhibition by amoxapine. N-[2-(p-Bromocinnamylamino)ethyl]-5-iso-quinolinesulphonamide (H-89), a protein kinase A (PKA) inhibitor, augmented IK amplitudes and completely eliminated amoxapine inhibition of IK. Amoxapine was also found to significantly increase intracellular cAMP levels. The effects of amoxapine on IK were abolished by preincubation with 5-hydroxytryptamine (5-HT) and the antagonists of 5-HT2 receptor. Moreover, intracellular application of guanosine 5′-[γthio]-triphosphate increased IK amplitudes and prevented amoxapine-induced inhibition. The selective Kv2.1 subunit blocker Jingzhaotoxin-III reduced IK amplitudes by 30% and also significantly abolished the inhibitory effect of amoxapine. Together these results suggest that amoxapine inhibits IK in mouse cortical neurons by cAMP/PKA-dependent pathway associated with the 5-HT receptor, and suggest that the Kv2.1 α-subunit may be the target for this inhibition.
Footnotes
This work was supported in part by the National Basic Research Program of China [Grant 2007CB512303]; Shanghai Leading Academic Discipline Project [Grant B111]; and the National Talent Training Fund in Basic Research of China [Grant J0630643].
Article, publication date, and citation information can be found at http://jpet.aspetjournals.org.
doi:10.1124/jpet.109.159160
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ABBREVIATIONS:
- TCA
- tricyclic antidepressant
- 5-HT
- 5-hydroxytryptamine
- IK
- delayed rectifier potassium current
- PKA
- protein kinase A
- ANOVA
- analysis of variance
- PBS
- phosphate-buffered saline
- HEK
- human embryonic kidney
- GTPγS
- guanosine 5′-[γ-thio]-triphosphate
- db-cAMP
- dibutyryl cAMP
- H-89
- N-[2-(p-bromocinnamylamino)ethyl]-5-iso-quinolinesulphonamide
- 4-AP
- 4-aminopyridine
- C6-ceramide
- dihydroceramide C6
- JZTX-III
- Jingzhaotoxin-III
- DMSO
- dimethyl sulfoxide
- IA
- transient potassium current.
- Received July 30, 2009.
- Accepted November 12, 2009.
- Copyright © 2010 by The American Society for Pharmacology and Experimental Therapeutics
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