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. Conclusion: 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.

3D-QSAR study indicates an enhancing effect of membrane ions on psychiatric drugs targeting serotonin receptor 5-HT1A

“…We obtained robust 3D-QSAR models when we included potassium, calcium and, especially iron ions, augmented by water. Our results are in agreement with experimental studies [31][32][33][34] indicating that the presence of iron, calcium or potassium ions is critical for antagonistic effects of psychiatric drugs at membrane receptors. Additionally we point that the effectiveness of antidepressants and antipsychotics is enhanced more by potassium and iron than by sodium.…”

“…Potassium and sodium ions are essential for all living cells, being especially important for neuron function, and for osmotic balance between cells and interstitial fluid. 32,38 Calcium homeostasis, especially in the context of the central nervous system, has crucial implications under many neuropsychiatric conditions. 30,31 It was reported that antipsychotic medication was not effective unless serum calcium and magnesium levels were both normal.…”

“…Experimental data confirm that calcium increased antidepressant activity, potassium increased the analgesic effect of antidepressants and Fe(III) increased the antioxidant effect of antipsychotics. [30][31][32][33][34] We will discuss in detail the role of ions in psychiatric diseases in the Experimental section. In agreement with these experimental studies, we present evidence that the 3D-QSAR-ALMOND method represents a suitable alternative to predict the antidepressant and antipsychotic activity of classical and, more importantly, of newly proposed psychiatric drugs.…”

Glucose-sensing glucagon-like peptide-1 receptor neurons in the dorsomedial hypothalamus regulate glucose metabolism

“…Instead, our data suggest that GLP-1R activation suppresses delayed rectifier potassium channel-mediated currents, rather than rapidly inactivating potassium currents, which results in the depolarization of the membrane potential. Previous studies showed that the cAMP-PKA pathway could suppress delayed rectifier K v channels (5,23,24,(52)(53)(54)(55); our work suggests that the GLP-1R activationinduced reduction of K v can also be controlled by cAMP-PKA activity. Thus, our data indicate that the signaling pathway involved in the GLP-1 regulation of DMH neurons can progress as follows: An elevation in intracellular cAMP levels activates PKA signaling, which leads to the blockade of the delayed rectifier potassium channel, resulting in postsynaptic neuronal depolarization and excitation (Fig.…”

Addition of amoxapine improves positive and negative symptoms in a patient with schizophrenia

“…It is a potent inhibitor of glycine transporters GLYT1b and GLYT2a [Núñez et al 2000], and it activates delta-opioid receptors in human frontal cortex in vitro [Onali et al 2010]. In addition, amoxapine has been shown to inhibit several K + channels including the voltage-gated K + [He et al 2010] and the G protein-activated inwardly rectifying K + (GIRK) channels [Kobayashi et al 2011] at micromolar concentrations, the same range as the brain concentration of the drug during treatment (5-67 μM); this effect seems to be mediated through serotonin and dopamine D1/D5 receptors [Yang et al 2011].…”