Diazepam and SL-327 synergistically attenuate anxiety-like behaviours in mice - Possible hippocampal MAPKs specificity.

Intracellular signalling pathways have been extensively studied as therapeutic targets for the treatment of mental diseases. Our attention has been caught by two kinases potentially involved in anxiety, ERK1/2 and CaMKII. The study aimed to examine changes in the activation of ERK1/2 and CaMKII concerning anxiolytic-like behaviours in mice. To evaluate anxiety-related response in mice, we used the open field test and the elevated plus maze test. Behavioural studies were complemented with the immunoblotting analysis to identify proteins of interest in the cortex, hippocampus, and striatum. We analysed the phosphorylation status of ERK1/2 and CaMKII in mice treated with a well-known anxiolytic drug - diazepam. Next, the blockade of ERK1/2 pathway by SL-327, a selective MEK1/2 inhibitor, was checked for anxiolytic action. Finally, the co-administration of subeffective doses of diazepam and SL-327 was investigated for a potential synergistic anxiolytic effect. Anxiolytic effects of acute diazepam are accompanied by decreased p-ERK1/2 and upregulation of p-CaMKII. Subchronic treatment with SL-327 leads to the manifestation of anxiolytic-like behaviours and changes in the phosphorylation status of both kinases in a diazepam-like manner. Co-administration of subeffective doses of SL-327 and diazepam induces anxiolysis, which is CaMKII-independent and correlates to selectively decreased phosphoactive ERK1/2 in the hippocampus. The MEK-ERK pathway is significantly involved in anxiolytic action of diazepam and its prolonged inhibition produces anxiolytic-like phenotype in mice. ERK inhibition could be used to manage anxiety symptoms in a benzodiazepine-sparing regimen for treatment of anxiety.