Neuronal and behavioral plasticity: the role of serotonin and BDNF systems tandem

On the interaction between BDNF and serotonin systems: The effects of long-term ethanol consumption in mice

We investigated the effect of chronic (6 weeks) consumption of 10% alcohol on the principal elements of BDNF (BDNF, proBDNF, p75, and TrkB receptors) and 5-HT (5-HT, 5-HIAA, tryptophan hydroxylase-2 [Tph-2], 5-HT transporter [5-HTT], 5-HT_1A, 5-HT_2A, and 5-HT₇ receptors) systems in the brain of C57Bl/6 mice. BDNF mRNA level in the raphe nuclei area and BDNF protein level in the hippocampus were lowered in ethanol-treated mice. The increase in proBDNF protein level in the raphe nuclei area, cortex, and amygdala and the increase of p75 receptor protein levels in the raphe nuclei area were revealed after ethanol exposure. Alcohol intake reduced the protein level and increased the activity of Tph-2, the key enzyme for serotonin biosynthesis in the brain, and increased the main 5-HT metabolite 5-HIAA level and 5-HIAA/5-НТ ratio as well as the 5-HT₇ receptor mRNA level in the raphe nuclei area. In the cortex, 5-HT_2A receptor protein level was reduced, and 5-HIAA/5-HT ratio was increased. These data showed considerable impact of alcoholization on the BDNF system, resulting in proBDNF and p75 receptor expression enhancement. Alcohol-induced changes in BDNF and 5-HT systems were revealed in the raphe nuclei area where the majority of the cell bodies of the 5-HT neurons are localized, as well as in the cortex, hippocampus, and amygdala. Our data suggest that the BDNF/5-HT interaction contributes to the mechanism underlying chronic alcohol-induced neurodegenerative disorders.

Exercise-Induced Elevated BDNF Level Does Not Prevent Cognitive Impairment Due to Acute Exposure to Moderate Hypoxia in Well-Trained Athletes

Exposure to acute hypoxia causes a detrimental effect on the brain which is also manifested by a decrease in the ability to perform psychomotor tasks. Conversely, brain-derived neurotrophic factor (BDNF), whose levels are elevated in response to exercise, is a well-known factor in improving cognitive function. Therefore, the aim of our study was to investigate whether the exercise under hypoxic conditions affects psychomotor performance. For this purpose, 11 healthy young athletes performed a graded cycloergometer exercise test to volitional exhaustion under normoxia and acute mild hypoxia (FiO₂ = 14.7%). Before, immediately after exercise and after a period of recovery, choice reaction time (CRT) and number of correct reactions (NCR) in relation to changes in serum BDNF were examined. Additionally, other selected factors which may modify BDNF production, i.e., cortisol (C), nitrite, catecholamines (adrenalin-A, noradrenaline-NA, dopamine-DA, serotonin-5-HT) and endothelin-1 (ET-1), were also measured. Exercise in hypoxic conditions extended CRT by 13.8% (p < 0.01) and decreased NCR (by 11.5%) compared to rest (p < 0.05). During maximal workload, NCR was lower by 9% in hypoxia compared to normoxia (p < 0.05). BDNF increased immediately after exercise in normoxia (by 29.3%; p < 0.01), as well as in hypoxia (by 50.0%; p < 0.001). There were no differences in BDNF between normoxia and hypoxia. Considering the fact that similar levels of BDNF were seen in both conditions but cognitive performance was suppressed in hypoxia, acute elevation of BDNF did not compensate for hypoxia-induced cognition impairment. Moreover, neither potentially negative effects of C nor positive effects of A, DA and NO on the brain were observed in our study.

Reduced serum VGF levels are linked with suicide risk in Chinese Han patients with major depressive disorder

BACKGROUND

VGF (nonacronymic) is a neuropeptide that plays an important role in the pathogenesis of major depressive disorder (MDD). However, no studies have yet investigated VGF levels in patients with MDD who are at risk of suicide. The purpose of the present study was to determine whether serum VGF levels are related to suicide risk in patients with MMD.

METHODS

A total of 107 patients with MDD and 40 normal control participated in the present study. The risk of suicide was assessed using the Nurses Global Assessment of Suicide Risk (NGASR). On this basis, 60 patients were assigned to a high-risk group (NGASR≥9) and 47 were assigned to a low-risk group (NGASR< 9). The severity of depression was measured using the 17-item Hamilton Depression Rating Scale (HDRS). Levels of serum VGF were determined using a double antibody sandwich enzyme-linked immunosorbent assay.

RESULTS

Serum VGF levels in the high-risk group (883.34 ± 139.67 pg/mL) were significantly lower than in the low-risk group (1020.56 ± 131.76 pg/mL) and in the control group (1107.00 ± 155.38 pg/mL) (F = 31.90, p < 0.001). In patients with MDD, suicide risk was significantly negatively correlated with VGF levels (r = - 0.55, p = 0.001).

CONCLUSIONS

Reduced serum VGF levels are related to risk of suicide in patients with MDD, so VGF may be a biomarker of suicide risk in MDD.

Biological bases of suicidal behaviours: A narrative review

Suicidal behaviour is a multifaceted phenomenon that concerns all human populations. It has been suggested that a complex interaction between the individual genetic profile and environmental factors throughout life underlies the pathophysiology of suicidal behaviour. Although epidemiological and genetic studies suggest the existence of a genetic component, exposure to biological and psychosocial adversities, especially during critical developmental periods, also contributes to altering the biological responses to threat and pleasure. This results in amplified maladaptive cognitive and behavioural traits and states associated with suicidal behaviours. Alterations in the cognitive inhibition and decision-making capacity have been implicated in suicidal behaviours. Structural and functional changes in key brain regions and networks, such as prefrontal cortex, insula and default mode network, may underlie this relationship. Furthermore, the shift from health to suicidal behaviour incorporates complex and dynamic changes in the immune and stress responses, monoaminergic system, gonadal system and neuroplasticity. In this review, we describe the major findings of epidemiological, genetic, neuroanatomical, neuropsychological, immunological and neuroendocrinological studies on suicide behaviours to provide a solid background for future research in this field. This broad overview of the biological bases of suicide should promote neuroscience research on suicidal behaviours. This might lead to improved biological models and to the identification of evidence-based biomarkers, treatment options and preventive strategies.