Effects of long-term agomelatine treatment on the cognitive performance and hippocampal plasticity of adult rats.

Agomelatine is an antidepressant with a distinct pharmacological mechanism of action as an MT1 and MT2 receptor agonist and as a 5-HT2C receptor antagonist. We evaluated the chronic effects of agomelatine administration (40 mg/kg, 20 weeks) on the cognitive performance of rats in the Morris water maze task. We applied unbiased stereological quantification methods to estimate the total numbers of granular and pyramidal neurons located in the dorsal hippocampus. We also analyzed the dendritic spines of pyramidal neurons in the CA1 region using the Golgi-Cox impregnation method. The agomelatine-treated group found the hidden platform more quickly than did the control group and spent significantly more time in the target quadrant. Agomelatine administration caused significant volumetric and numerical enhancements in granular and pyramidal neurons in the dentate gyrus and CA1-3 subregions, respectively. Increased densities of the mushroom and stubby types of spines, with no alteration in the thin-shaped spines, were observed in the agomelatine-treated group. These results showed that long-term agomelatine administration induced a nootropic effect supported by structural changes. Enhancement of the more stable types of dendritic spines might indicate improved adaptive capacity in hippocampal neurons. Future studies will provide a better understanding of the effect of this drug on synaptic plasticity.

Synthesis of new 1-phenyl-2-(4-substituted-piperazin-1-yl)-propanol derivatives and evaluation of their antidepressant-like effects.

In this study, we synthesized eight novel 1-phenyl-2-(4-substituted-piperazin-1-yl)-propanol derivatives and evaluated their antidepressant-like activities. The chemical structures of the synthesised compounds were elucidated by spectroscopy and elemental analyses. Potential antidepressant-like effects of the test compounds (20 mg kg(-1)) were investigated using the tail-suspension test and modified forced swimming test (MFST) in mice. Additionally, the spontaneous locomotor activity of the mice was assessed using the activity cage apparatus. Both the reference drug fluoxetine (20 mg kg(-1)) and the test compounds 3a-3e and 3g significantly shortened the immobility time of the mice in both the behavioural tests. These test compounds also increased the swimming time in MFST without any change in the climbing duration. Compounds 3c-3e and 3g were significantly more potent in inducing these effects than 3a and 3b. None of the compounds changed the locomotor activities of the animals, thus antidepressant-like effects of test compounds were specific. The findings support those of previous studies that reported antidepressant-like activities of aryl alkanol piperazine derivatives.

Anti-depressant-like effect of vitexin in BALB/c mice and evidence for the involvement of monoaminergic mechanisms.

The present study was designed to investigate the putative effect of vitexin, a flavone C-glucoside present in some drugs, medicinal plants and nutraceuticals, on the central nervous system. Vitexin (10-30 mg/kg) did not show significant alterations in the behaviour of mice tested in hole-board, plus-maze or activity cage tests. However, immobility time of the mice significantly reduced by vitexin administrations in both the tail-suspension and modified forced swimming tests. The anti-immobility effect of vitexin in the tail-suspension test was reversed with α-methyl-para-tyrosine methyl ester (AMPT, an inhibitor of catecholamine synthesis, 100mg/kg, i.p.), yohimbine (an α(2)-adrenoceptor antagonist, 1mg/kg, i.p.), NAN 190 (a 5-HT(1A) antagonist, 0.5mg/kg, i.p.), SCH 23390 (a dopamine D(1) antagonist, 0.05 mg/kg, s.c.) and sulpiride (a dopamine D(2)/D(3) antagonist, 50mg/kg, i.p.). The same effect was not reversed, however, by p-chlorophenylalanine methyl ester (PCPA; an inhibitor of serotonin synthesis 100mg/kg, i.p., administered for 4 consecutive days), ketanserin (a 5-HT(2A/2C) antagonist, 1-4 mg/kg, i.p.), ondansetron (a 5-HT(3) antagonist, 0.1-0.4 mg/kg, i.p.), prazosin (an α(1)-adrenoceptor antagonist, 1-4 mg/kg, i.p.), or propranolol (a non-selective ß-adrenoceptor antagonist, 5-20mg/kg, i.p.). These results suggest that the anti-depressant-like effect of vitexin is mediated through an increase in catecholamine levels in the synaptic cleft as well as through interactions with the serotonergic 5-HT(1A), noradrenergic α(2), and dopaminergic D(1), D(2), and D(3) receptors. To our knowledge, this is the first study to show findings that indicate an anti-depressant-like effect of vitexin and its underlying mechanisms.