Melatonin synergizes with citalopram to induce antidepressant-like behavior and to promote hippocampal neurogenesis in adult mice.

Adult hippocampal neurogenesis is affected in some neuropsychiatric disorders such as depression. Numerous evidence indicates that plasma levels of melatonin are decreased in depressed patients. Also, melatonin exerts positive effects on the hippocampal neurogenic process and on depressive-like behavior. In addition, antidepressants revert alterations of hippocampal neurogenesis present in models of depression following a similar time course to the improvement of behavior. In this study, we analyzed the effects of both, citalopram, a widely used antidepressant, and melatonin in the Porsolt forced swim test. In addition, we investigated the potential antidepressant role of the combination of melatonin and citalopram (MLTCITAL), its type of pharmacological interaction on depressive behavior, and its effect on hippocampal neurogenesis. Here, we found decreased immobility behavior in mice treated with melatonin (<14-33%) and citalopram (<17-30%). Additionally, the MLTCITAL combination also decreased immobility (<22-35%) in comparison with control mice, reflecting an antidepressant-like effect after 14 days of treatment. Moreover, MLTCITAL decreased plasma corticosterone levels (≤13%) and increased cell proliferation (>29%), survival (>39%), and the absolute number of -associated new neurons (>53%) in the dentate gyrus of the hippocampus. These results indicate that the MLTCITAL combination exerts synergism to induce an antidepressant-like action that could be related to the modulation of adult hippocampal neurogenesis. This outcome opens the opportunity of using melatonin to promote behavioral benefits and hippocampal neurogenesis in depression and also supports the use of the MLTCITAL combination as an alternative to treat depression.

The neurogenic effects of an enriched environment and its protection against the behavioral consequences of chronic mild stress persistent after enrichment cessation in six-month-old female Balb/C mice.

Because stress may underlie the presence of depressive episodes, strategies to produce protection against or to reverse the effects of stress on neuroplasticity and behavior are relevant. Preclinical studies showed that exposure to stimuli, such as physical activity and environmental enrichment (ENR), produce beneficial effects against stress causing antidepressant-like effects in rodents. Additionally, ENR induces positive effects on neuroplasticity, neurochemistry and behavior at any age of rodents tested. Here, we analyzed whether ENR exposure prevents the development of depressive-like behavior produced by unpredictable, chronic mild stress (CMS) exposure as well as changes in hippocampal neurogenesis in a six-month-old female Balb/C mice, strain that shows low baseline levels of hippocampal neurogenesis. Mice were assigned to one of four groups: (1) normal housing-normal housing (NH-NH), (2) NH-CMS, (3) ENR-NH, or (4) ENR-CMS. The animals were exposed over 46 days to ENR or NH and subsequently to NH or CMS for 4 weeks. ENR induces long-term effects protecting against CMS induction of anhedonia and hopelessness behaviors. Independent of housing conditions, ENR increased the number of proliferative cells (Ki67), and CMS decreased the number of proliferative cells. ENR increased the newborn cells (BrdU) and mature phenotypes of neurons; these effects were not changed by CMS exposure. Similarly, the number of doublecortin-positive cells was not affected by CMS in ENR mice, which showed more cells with complex dendrite arborizations. Our study suggests that ENR induces protection against the effects of CMS on behavior and neuroplasticity in six-month-old Balb/C mice.

Resveratrol Enhances Neuroplastic Changes, Including Hippocampal Neurogenesis, and Memory in Balb/C Mice at Six Months of Age.

Resveratrol (RVTL) is a flavonoid found in red wine and has been publicized heavily as an anti-aging compound. Indeed, basic research confirms that although there is much hype in the promotion of RVTL, flavonoids such as RVTL have a wide range of biological effects. We here investigated the effects of RVTL treatment on hippocampal plasticity and memory performance in female Balb/C mice, a strain with low baseline levels of adult neurogenesis. Two weeks of treatment with RVTL (40 mg/kg) induced the production of new neurons in vivo by increasing cell survival and possibly precursor cell proliferation. In addition, RVTL decreased the number of apoptotic cells. The number of doublecortin (DCX)-expressing intermediate cells was increased. RVTL stimulated neuronal differentiation in vitro without effects on proliferation. In the dentate gyrus, RVTL promoted the formation and maturation of spines on granule cell dendrites. RVTL also improved performance in the step down passive avoidance test. The RVTL-treated mice showed increase in the levels of two key signaling proteins, phospho-Akt and phospho-PKC, suggesting the involvement of these signaling pathways. Our results support the vision that flavonoids such as resveratrol deserve further examination as plasticity-inducing compounds in the context of successful cognitive aging.

Melatonin maintains calcium-binding calretinin-positive neurons in the dentate gyrus during aging of Balb/C mice.

Melatonin, the main product synthesized by the pineal gland, modulates several brain functions through different mechanisms, some of them involving the activation or participation of calcium binding intracellular proteins, such as the alpha calcium dependent protein kinase C and calmodulin. Another calcium-binding protein is calretinin, which exerts an essential role for adult hippocampal neurogenesis. Melatonin favors calretinin-positive neurons in the dentate gyrus (DG) of young mice but hippocampal neurogenesis and plasma levels of melatonin decrease during aging. Thus, in this study, we analyzed the impact of exogenous supplementation with melatonin in calretinin-neurons and their distribution along the dorsal-ventral DG in the hippocampus at three different time points (1, 3, or 6 months) after daily treatment with melatonin (8 mg/kg) in male Balb/C mice. We found an increase in the number of calretinin-positive neurons in the DG after treatment (>66%). Although a significant decline in the number of calretinin-neurons was found in both treated (~60.46-69.56%) and untreated mice (~68.81-70.34%) with respect to the youngest mice analyzed, melatonin still maintained higher number of cells in the DG. Also, the distribution of calretinin-neurons along the dorsal-ventral DG significantly showed more cells in the ventral-DG of mice treated with melatonin. Together, the data suggest that melatonin also acts on calretinin in the DG, supporting it as a molecule connecting calcium signaling and neuronal development.

3111T/C clock gene polymorphism is not associated with sleep disturbances in untreated depressed patients.

Sleep patterns, frequently altered in depression, have been hypothesized to be under genetic control. The circadian locomotor output cycles kaput (CLOCK) T3111C variant has been studied in association with sleep disturbances in depressed patients. The aim of this study was to investigate possible effects of T3111C CLOCK on insomnia, daytime sleepiness, sleep quality, and depression severity in a sample of 100 major depressive disorder patients. Inclusion criteria were: major depressive disorder, drug-free for any antidepressant and/or benzodiazepines for at least four weeks previously to the study, and a minimum score of >17 on the Hamilton Rating Scale for Depression. The Morningness-Eveningness Questionnaire, Epworth Sleepiness Scale, Athens Insomnia Scale, and Pittsburgh Sleep Quality Index were applied. No significant difference was found concerning genotype or allele groups and Hamilton Rating Scale for Depression items or clusters. No difference was found between genotypes and comorbidity, chronotype distribution, Epworth Sleepiness Scale, Athens Insomnia Scale, or Pittsburgh Sleep Quality Index total scores. Overall, the present findings did not support the hypothesis of an effect of the T3111C CLOCK variant on sleep disturbances in major depressive disorder. Further analysis of clock machinery will clarify the contribution of clock genes to the maintenance of mental health.

Distribution of apolipoprotein E alleles in coras and huicholes from Nayarit and Nahuas and Mestizos from Veracruz, Mexico.

We report allele frequencies for the most common polymorphism of the APOE gene in Mexican individuals from two regions not previously described: Coras and Huicholes from Nayarit, and Nahuas and mestizos from Veracruz. We also report APOE allele frequencies for inhabitants of Mexico City. These descriptive data underscore the allelic heterogeneity for this particular locus in Mexico.