Methamphetamine reversed maternal separation-induced decrease in nerve growth factor in the ventral hippocampus

Partial Improvement of Spatial Memory Damages by Bone Marrow Mesenchymal Stem Cells Transplantation Following Trimethyltin Chloride Administration in the Rat CA1

Introduction:

Trimethyltin Chloride (TMT) is a neurotoxin that can kill neurons in the nervous system and activate astrocytes. This neurotoxin mainly damages the hippocampal neurons. After TMT injection, behavioral changes such as aggression and hyperactivity have been reported in animals along with impaired spatial and learning memory. Hence, TMT is a suitable tool for an experimental model of neurodegeneration. The present study aims to determine the palliative effects of Bone Marrow-derived Mesenchymal Stem Cells (BM-MSCs) on the hippocampi of rats damaged from TMT exposure.

Methods:

We assigned 28 male Wistar rats to the following groups: control, model, vehicle, and treatment. The groups received Intraperitoneal (IP) injections of 8 mg/kg TMT. After one week, stem cells were stereotactically injected into the CA1 of the right rats’ hippocampi. Spatial memory was determined by the Morris Water Maze (MWM) test 6 weeks after cell transplantation. Finally, the rats’ brains were perfused and stained by cresyl violet to determine the numbers of cells in the Cornus Ammonis (CA1) section of the hippocampus. We assessed the expressions of Glial Fibrillary Acidic Protein (GFAP) and Neuronal-specific Nuclear (NeuN) proteins in the right hippocampus by Western blot.

Results:

The MWM test showed that the treatment group had significantly higher traveled distances in the target quarter compared with the model and vehicle groups (P<0.05). Based on the result of cell count (Nissl staining), the number of cells increased in the treatment group compared with the model and vehicle groups (P<0.05). Western blot results showed up-regulation of GFAP and NeuN proteins in the model, vehicle, and treatment groups compared with the control group.

Conclusion:

Injection of BM-MSCs may lead to a behavioral and histological improvement in TMT-induced neurotoxicity by increasing the number of pyramidal neurons and improving memory.

Maternal Deprivation and Sex Alter Central Levels of Neurotrophins and Inflammatory Cytokines in Rats Exposed to Palatable Food in Adolescence

Maternal deprivation (MD) in rodents is used to simulate human-infant early life stress, which leads to neural, hormonal, and behavioral alterations. Palatable food (PF) can reduce the stress response, and individuals use it as a self-applied stress relief method. Thus, the present study aimed to evaluate the effect of the association between MD in the early life (P1-P10) and PF consumption (condensed milk, P21-P44) in the central neuroplasticity (BDNF/NGF levels) and central neuroinflammatory parameters (TNF-α, IL-6, and IL-10 levels) in male and female Wistar rats in the adolescence. In addition, weight-related parameters (weight gain, Lee Index, and relative adipose tissue weight) were evaluated. PF exposure increased relative adipose tissue weight; however, it did not lead to a change in animals' body weight. MD reduced hypothalamic BDNF and NGF levels, and hippocampal TNF-α levels in male and female rats. Animals of both sexes that received PF, exhibited reduced hypothalamic NGF levels. Neuroinflammatory marker evaluations showed that male rats were more susceptible to the interventions than female rats, since MD reduced their cortical IL-10 levels and PF increased their IL-6 levels. Differences in the Lee index, central BDNF, TNF-α, and IL-6levels were observed between sexes. Male animals per se presented greater Lee index. Female rats had higher BDNF and IL-6 levels in the hippocampus and hypothalamus and higher hypothalamic TNF-α levels than those observed in males. In conclusion, there were more noticeable effects of MD than PF on the variables measured in this study. Sex effect was identified as an important factor and influenced most of the neurochemical measures in this study. In this way, we suggest including both female and male animals in researches to improve the quality of translational studies.

Methamphetamine binge administration during late adolescence induced enduring hippocampal cell damage following prolonged withdrawal in rats

A recent study from our laboratory demonstrated that binge methamphetamine induced hippocampal cell damage (i.e., impaired cell genesis) in rats when administered specifically during late adolescence (postnatal day, PND 54-57) and evaluated 24 h later (PND 58). The results also suggested a possible role for brain-derived neurotrophic factor (BDNF) regulating cell genesis and survival. This subsequent study evaluated whether these effects persisted in time as measured following prolonged withdrawal. Male Sprague-Dawley rats were treated (i.p.) with BrdU (2 × 50 mg/kg, 3 days, PND 48-50) followed by a binge paradigm (3 pulses/day, every 3 h, 4 days, PND 54-57) of methamphetamine (5 mg/kg, n = 14, M) or saline (0.9% NaCl, 1 ml/kg, n = 12, C). Following 34 days of forced withdrawal (PND 91), rats were killed 45 min after a challenge dose of saline (Sal: C-Sal, n = 6; M-Sal, n = 7) or methamphetamine (Meth: C-Meth, n = 6; M-Meth, n = 7). Neurogenesis markers (Ki-67: cell proliferation; NeuroD: early neuronal survival; BrdU: prolonged cell survival, 41-43 days old cells) were evaluated by immunohistochemistry while neuroplasticity markers (BDNF and Fos forms) were evaluated by Western blot. The main results showed that a history of methamphetamine administration (PND 54-57) induced enduring hippocampal cell damage (i.e., observed on PND 91) by decreasing cell survival (BrdU + cells) and mature-BDNF (m-BDNF) protein content, associated with neuronal survival, growth and differentiation. Interestingly, m-BDNF regulation paralleled hippocampal c-Fos protein content, indicating decreased neuronal activity, and thus reinforcing the persisting negative effects induced by methamphetamine in rat hippocampus following prolonged withdrawal.

The long-term effects of methamphetamine exposure during pre-adolescence on depressive-like behaviour in a genetic animal model of depression

Methamphetamine (METH) is a psychostimulant and drug of abuse, commonly used early in life, including in childhood and adolescence. Adverse effects include psychosis, anxiety and mood disorders, as well as increased risk of developing a mental disorder later in life. The current study investigated the long-term effects of chronic METH exposure during pre-adolescence in stress-sensitive Flinders Sensitive Line (FSL) rats (genetic model of depression) and control Flinders Resistant Line (FRL) rats. METH or vehicle control was administered twice daily from post-natal day 19 (PostND19) to PostND34, followed by behavioural testing at either PostND35 (early effects) or long-lasting after withdrawal at PostND60 (early adulthood). Animals were evaluated for depressive-like behaviour, locomotor activity, social interaction and object recognition memory. METH reduced depressive-like behaviour in both FSL and FRL rats at PostND35, but enhanced this behaviour at PostND60. METH also reduced locomotor activity on PostND35 in both FSL and FRL rats, but without effect at PostND60. Furthermore, METH significantly lowered social interaction behaviour (staying together) in both FRL and FSL rats at PostND35 and PostND60, whereas self-grooming time was significantly reduced only at PostND35. METH treatment enhanced exploration of the familiar vs. novel object in the novel object recognition test (nORT) in FSL and FRL rats on PostND35 and PostND60, indicative of reduced cognitive performance. Thus, early-life METH exposure induce social and cognitive deficits. Lastly, early-life exposure to METH may result in acute antidepressant-like effects immediately after chronic exposure, whereas long-term effects after withdrawal are depressogenic. Data also supports a role for genetic predisposition as with FSL rats.

Behavioural and biochemical changes in maternally separated Sprague-Dawley rats exposed to restraint stress

Early life adversity has been associated with the development of various neuropsychiatric disorders in adulthood such as depression and anxiety. The aim of this study was to determine if stress during adulthood can exaggerate the depression-/anxiety-like behaviour observed in the widely accepted maternally separated (MS) Sprague-Dawley (SD) rat model of depression. A further aim was to determine whether the behavioural changes were accompanied by changes in hippocampal brain-derived neurotrophic factor (BDNF) and the protein profile of the prefrontal cortex (PFC). Depression-/anxiety-like behaviour was measured in the elevated plus maze, open field and forced swim test (FST) in the MS SD rats exposed to chronic restraint stress in adulthood. As expected, MS increased immobility of SD rats in the FST but restraint stress did not enhance this effect of MS on SD rats. A proteomic analysis of the PFC revealed a decrease in actin-related proteins in MS and non-separated rats subjected to restraint stress as well as a decrease in mitochondrial energy-related proteins in the stressed rat groups. Since MS during early development causes a disruption in the hypothalamic-pituitary-adrenal axis and long-term changes in the response to subsequent stress, it may have prevented restraint stress from exerting its effects on behaviour. Moreover, the decrease in proteins related to mitochondrial energy metabolism in MS rats with or without subsequent restraint stress may be related to stress per se and not depression-like behaviour, because rats subjected to restraint stress displayed similar decreases in energy-related proteins and spent less time immobile in the FST than control rats.

Early Life Stress Effects on Glucocorticoid-BDNF Interplay in the Hippocampus

Early life stress (ELS) is implicated in the etiology of multiple psychiatric disorders. Important biological effects of ELS are manifested in stress-susceptible regions of the hippocampus and are partially mediated by long-term effects on glucocorticoid (GC) and/or neurotrophin signaling pathways. GC-signaling mediates the regulation of stress response to maintain homeostasis, while neurotrophin signaling plays a key role in neuronal outgrowth and is crucial for axonal guidance and synaptic integrity. The neurotrophin and GC-signaling pathways co-exist throughout the central nervous system (CNS), particularly in the hippocampus, which has high expression levels of glucocorticoid-receptors (GR) and mineralocorticoid-receptors (MR) as well as brain-derived neurotrophic factor (BDNF) and its receptor, tropomyosin-related kinase receptor B (TrkB). This review addresses the effects of ELS paradigms on GC- and BDNF-dependent mechanisms and their crosstalk in the hippocampus, including potential implications for the pathogenesis of common stress-related disorders.

Alteration of somatosensory response in adulthood by early life stress

Early life stress is well-known as a critical risk factor for mental and cognitive disorders in adulthood. Such disorders are accompanied by altered neuro- (synapto-) genesis and gene expression. Because psychosomatic disorders induced by early life stress (e.g., physical and/or sexual abuse, and neglect) have become a socio-economic problem, it is very important to clarify the mechanisms underlying these changes. However, despite of intensive clinical and animal studies, such mechanisms have not yet been clarified. Although the disturbance of glucocorticoid and glutamate homeostasis by stress has been well-documented, it has not yet been clarified whether such disturbance by early life stress persists for life. Furthermore, since previous studies have focused on the detection of changes in specific brain regions, such as the hippocampus and prefrontal cortex, it has not been clarified whether early life stress induced changes in the sensory/motor system. Thus, in this review, we introduce recent studies on functional/structural changes in the somatosensory cortex induced by early life stress. We believe that this review provides new insights into the functional alteration of the somatosensory system induced by early life stress. Such information may have clinical relevance in terms of providing effective therapeutic interventions to early life stressed individuals.