Mirtazapine exerts an anxiolytic-like effect through activation of the median raphe nucleus-dorsal hippocampal 5-HT pathway in contextual fear conditioning in rats

The functional role of serotonergic projections from the median raphe nucleus (MRN) to the dorsal hippocampus (DH) in anxiety remains understood poorly. The purpose of the present research was to examine the functional role of this pathway, using the contextual fear conditioning (CFC) model of anxiety. We show that intra-MRN microinjection of mirtazapine, a noradrenergic and specific serotonergic antidepressant, reduced freezing in CFC without affecting general motor activity dose-dependently, suggesting an anxiolytic-like effect. In addition, intra-MRN microinjection of mirtazapine dose-dependently increased extracellular concentrations of serotonin (5-HT) but not dopamine in the DH. Importantly, intra-DH pre-microinjection of WAY-100635, a 5-HT1A antagonist, significantly attenuated the effect of mirtazapine on freezing. These results, for the first time, suggest that activation of the MRN-DH 5-HT1A pathway exerts an anxiolytic-like effect in CFC. This is consistent with the literature that the hippocampus is essential for retrieval of contextual memory and that 5-HT1A receptor activation in the hippocampus primarily exerts an inhibitory effect on the neuronal activity

Association between suicide-related ideations and affective temperaments in the Japanese general adult population

Background: Suicide rates are vastly higher in Japan than in many other countries, although the associations between affective temperaments and suicide-related ideations in the general adult population remain unclear. Therefore, we aimed to elucidate these associations in the present study. Methods: We analyzed data from 638 Japanese volunteers who completed both the Patient Health Questionnaire (PHQ-9) and the Temperament Evaluation of the Memphis, Pisa, Paris, and San Diego Auto-questionnaire (TEMPS-A). Participants were then divided into three groups based on PHQ-9 summary scores and responses to the suicide-related ideation item: non-depressive control group (NC; N = 469), depressive symptoms without suicide-related ideations group (non-SI; N = 135), and depressive symptoms with suicide-related ideations group (SI; N = 34). The depressive symptoms were defined for PHQ-9 summary scores ≥5, and the suicide-related ideations were defined for PHQ-9 #9 score ≥1. We then compared TEMPS-A scores among the groups using Kruskal-Wallis tests. Then the 95% confidence intervals of differences in TEMPS-A subscale scores between the NC and non-SI groups, or between NC and SI groups, were calculated. Results: Participants of the SI group exhibited significantly higher scores on the depressive, irritable, and anxious temperament subscales than those of the non-SI group. Similarly, women of the SI group exhibited significantly higher scores of the depressive and irritable temperament subscales than women of the non-SI group, while men of the SI group exhibited significantly higher depressive temperament scores than those of the non-SI group. Among all participants and only men, cyclothymic subscale scores were higher in those of the SI group than the non-SI group (not significant), although the 95% confidence intervals did not overlap. Limitations: The cross-sectional study design was the main limitation. Conclusions: Depressive, irritable, and anxious temperaments are significant risk factors for suicide-related ideations in the Japanese general adult population. Furthermore, irritable temperament in women and depressive temperament in men are associated with suicide-related ideations

Magnifying Endoscopy with Blue Laser Imaging Improves the Microstructure Visualization in Early Gastric Cancer: Comparison of Magnifying Endoscopy with Narrow-Band Imaging

Backgrounds. Magnifying endoscopy with blue laser imaging (ME-BLI) for diagnosis of early gastric cancer (EGC) is as effective as magnifying endoscopy with narrow-band imaging (ME-NBI). However, there are different EGCs in microstructure visualization between ME-BLI and ME-NBI. This study aimed to clarify the pathological features of the EGCs, in which microstructure visualization was different between ME-NBI and ME-BLI. Methods. EGCs were classified into groups A (irregular microsurface pattern (MSP) in ME-BLI and absent MSP in ME-NBI), B (irregular MSP in two modalities), or C (absent MSP in two modalities), according to the vessel plus surface classification. We compared the pathological features of EGCs between the three groups. Results. 17, four, and five lesions could be evaluated in detail in groups A, B and C, respectively. Well-differentiated adenocarcinomas with shallow crypts were more frequent in group A than in group B (58.8 and 0%, resp.). The mean crypt depth of group A was significantly shallower than that of group B (56 ± 20, 265 ± 64 μm, resp., P=0.0002). Conclusions. ME-BLI could better visualize the microstructures of the EGCs with shallow crypts compared with ME-NBI. Therefore, ME-BLI could enable a more accurate diagnosis of EGC with shallow crypts

Combined treatment with MAO-A inhibitor and MAO-B inhibitor increases extracellular noradrenaline levels more than MAO-A inhibitor alone through increases in β-phenylethylamine

Monoamine oxidase inhibitors (MAO inhibitors) have been widely used as antidepressants. However, it remains unclear whether a difference exists between non-selective MAO inhibitors and selective MAO-A inhibitors in terms of their antidepressant effects. Using in vivo microdialysis methods, we measured extracellular noradrenaline and serotonin levels following administration of Ro 41-1049, a reversible MAO-A inhibitor and/or lazabemide, a reversible MAO-B inhibitor in the medial prefrontal cortex (mPFC) of rats. We examined the effect of local infusion of β-phenylethylamine to the mPFC of rats on extracellular noradrenaline and serotonin levels. Furthermore, the concentrations of β-phenylethylamine in the tissue of the mPFC after combined treatment with Ro 41-1049 and lazabemide were measured. The Ro 41-1049 alone and the combined treatment significantly increased extracellular noradrenaline levels compared with vehicle and lazabemide alone. Furthermore, the combined treatment increased noradrenaline levels significantly more than Ro 41-1049 alone did. The Ro 41-1049 alone and the combined treatment significantly increased extracellular serotonin levels compared with vehicle and lazabemide alone, but no difference in serotonin levels was found between the combined treatment group and the Ro 41-1049 group. Local infusion of low-dose β-phenylethylamine increased extracellular noradrenaline levels, but not that of serotonin. Only the combined treatment significantly increased β-phenylethylamine levels in tissues of the mPFC. Our results suggest that the combined treatment with a MAO-A inhibitor and a MAO-B inhibitor strengthens antidepressant effects because the combined treatment increases extracellular noradrenaline levels more than a MAO-A inhibitor alone through increases in β-phenylethylamine

Effect of triiodothyronine (T3) augmentation of acute milnacipran administration on monoamine levels: an in vivo microdialysis study in rats

Background: Up to 30% of depressed patients are partially or totally resistant to antidepressant therapy. The administration of triiodothyronine (T3) to antidepressant nonresponders can be an effective augmentation strategy, although the mechanism is not fully understood. Methods: In vivo microdialysis was used to examine the effect of T3 augmentation of the antidepressant, milnacipran. Basal extracellular serotonin, norepinephrine, and dopamine levels were measured before and after acute milnacipran administration in the medial prefrontal cortex and amygdala of rats which had received subchronic (7 days) T3 treatment or control saline. Results: Subchronic administration of T3 at 0.1 mg/kg significantly increased basal extracellular levels of serotonin in the medial prefrontal cortex, but not in the amygdala. In contrast, subchronic administration of T3 at 0.2 mg/kg did not alter basal extracellular serotonin levels in the medial prefrontal cortex. Basal extracellular levels of norepinephrine and dopamine were not modified by either dose of T3 in either region. Acute administration of milnacipran, a serotonin-norepinephrine reuptake inhibitor, to control animals resulted in a significant increase of extracellular levels of serotonin, norepinephrine, and dopamine. When administered to animals treated subchronically with T3 at 0.1 mg/kg, milnacipran produced an additional increase in extracellular serotonin levels but not in levels of norepinephrine or dopamine in the medial prefrontal cortex of rats. Conclusion: These results suggest that the mechanism of the augmentation effect of milnacipran by T3 administration occurs via enhancement of serotonergic neurotransmission, but not through noradrenergic or dopaminergic neurotransmission

Combined treatment with subchronic lithium and acute intracerebral mirtazapine microinjection into the median raphe nucleus exerted an anxiolytic-like effect synergistically

Although preclinical and clinical studies have established the efficacy of lithium augmentation of antidepressant drugs, the mechanism of action of lithium augmentation is not fully understood. Our previous study reported that subchronic lithium treatment enhanced the anxiolytic-like effect of systemic mirtazapine. In the present study, we examined the effect of subchronic lithium in combination with acute local intracerebral injection of mirtazapine on fear-related behaviors in a contextual fear conditioning test in rats to clarify the target brain region of lithium augmentation of mirtazapine. After conditioning by footshock, diet (food pellets) containing Li2CO3 at a concentration of 0.2% was administered for 7 days. Ten min before testing and 7 days after conditioning, mirtazapine (3 μg/site) in a volume of 0.5 µl was acutely injected into the median raphe nucleus (MRN), hippocampus or amygdala. The combination of subchronic lithium and acute mirtazapine microinjection into the MRN but not the hippocampus or the amygdala reduced fear expression synergistically. These results suggest that intra-MRN mirtazapine treatment with subchronic lithium exerts the anxiolytic-like effect through the facilitation of the MRN-5HT pathway