Serotonin limits generation of chromaffin cells during adrenal organ development.

Adrenal glands are the major organs releasing catecholamines and regulating our stress response. The mechanisms balancing generation of adrenergic chromaffin cells and protecting against neuroblastoma tumors are still enigmatic. Here we revealed that serotonin (5HT) controls the numbers of chromaffin cells by acting upon their immediate progenitor "bridge" cells via 5-hydroxytryptamine receptor 3A (HTR3A), and the aggressive HTR3Ahigh human neuroblastoma cell lines reduce proliferation in response to HTR3A-specific agonists. In embryos (in vivo), the physiological increase of 5HT caused a prolongation of the cell cycle in "bridge" progenitors leading to a smaller chromaffin population and changing the balance of hormones and behavioral patterns in adulthood. These behavioral effects and smaller adrenals were mirrored in the progeny of pregnant female mice subjected to experimental stress, suggesting a maternal-fetal link that controls developmental adaptations. Finally, these results corresponded to a size-distribution of adrenals found in wild rodents with different coping strategies.

Analysis of Antidepressant-like Effects and Action Mechanisms of GSB-106, a Small Molecule, Affecting the TrkB Signaling.

Induction of BDNF-TrkB signaling is associated with the action mechanisms of conventional and fast-acting antidepressants. GSB-106, developed as a small dimeric dipeptide mimetic of BDNF, was previously shown to produce antidepressant-like effects in the mouse Porsolt test, tail suspension test, Nomura water wheel test, in the chronic social defeat stress model and in the inflammation-induced model of depression. In the present study, we evaluated the effect of chronic per os administration of GSB-106 to Balb/c mice under unpredictable chronic mild stress (UCMS). It was observed for the first time that long term GSB-106 treatment (1 mg/kg, 26 days) during ongoing UCMS procedure ameliorated the depressive-like behaviors in mice as indicated by the Porsolt test. In addition, chronic per os administration of GSB-106 resulted in an increase in BDNF levels, which were found to be decreased in the prefrontal cortex and hippocampus of mice after UCMS. Furthermore, prolonged GSB-106 treatment was accompanied by an increase in the content of pTrkB706/707 in the prefrontal cortex and by a pronounced increase in the level of pTrkB816 in both studied brain structures of mice subjected to UCMS procedure. In summary, the present data show that chronic GSB-106 treatment produces an antidepressant-like effect in the unpredictable chronic mild stress model, which is likely to be associated with the regulation of the BDNF-TrkB signaling.

Antidepressant-like effect of fluoxetine may depend on translocator protein activity and pretest session duration in forced swimming test in mice.

The antidepressant-like effect of fluoxetine (20 mg/kg i.p.) has been assessed using the forced swimming test (FST) in IRC (CD-1) mice exposed or not to a pretest session of different duration (5 or 20 min). The influence of the mitochondrial translocator protein (TSPO) activity on the antidepressant-like effect of fluoxetine (20 mg/kg i.p.) in the FST was also studied. The antidepressant-like effect of fluoxetine was observed only in mice subjected to a 5-min pretest session 24 h before the FST. The TSPO antagonist PK11195 [1-(2-chlorophenyl)-N-methyl-N-(1-methylpropyl)-3-isoquinolinecarboxamide; 1 or 3 mg/kg i.p.] inhibited the antidepressant activity of fluoxetine in the FST. In the present study, fluoxetine or PK11195 was administered for a short duration. We suppose that the functional activity of TSPO may depend on a pretest session and that using this procedure is necessary to detect antidepressant activity of fluoxetine-like drugs.

Pharmacological Aspects of Neuro-Immune Interactions.

The use of systematic approach for the analysis of mechanism of action of drugs at different levels of biological organization of organisms is an important task in experimental and clinical pharmacology for drug designing and increasing the efficacy and safety of drugs. The analysis of published data on pharmacological effects of psychotropic drugs possessing immunomodulatory and/or antiviral properties have shown a correlation between central effects of examined drugs associated with the impact on the processes of neurogenesis of adult brain and survival of neurons, and their ability to alter levels of key proinflammatory cytokines. The changes that occur as a result of the influence of pharmacological agents at one of the systems should inevitably lead to the functional reorganization at another. Integrative mechanisms underlying the neuro-immune interactions may explain the "pleiotropic" pharmacological effects of some antiviral and immunomodulatory drugs. Amantadine, which was originally considered as an antiviral agent, was approved as anti-parkinsonic drug after its wide medical use. The prolonged administration of interferon alpha caused depression in 30-45% of patients, thus limiting its clinical use. The antiviral drug "Oseltamivir" may provoke the development of central side effects, including abnormal behavior, delirium, impaired perception and suicides. Anti-herpethetical drug "Panavir" shows pronounced neuroprotective properties. The purpose of this review is to analyze the experimental and clinical data related to central effects of drugs with antiviral or/and immunotropic activity, and to discover the relationship of these effects with changes in reactivity of immune system and proinflammatory response.