Developmental effects of environmental enrichment on selective and auditory sustained attention

Environmental enrichment initiated in adolescence restores the reduced expression of synaptophysin and GFAP in the hippocampus of chronically stressed rats in a sex-specific manner

This study aims at investigating whether environmental enrichment (EE) initiated in adolescence can alter chronic unpredictable stress (CUS)-associated changes in astroglial and synaptic plasticity markers in male and female rats. To this end, we studied possible alterations in hippocampal glial fibrillary acidic protein (GFAP) and synaptophysin (SYN) in CUS rats previously housed in EE. Wistar rats on postnatal day (PND) 23 were housed for 10 weeks in standard housing (SH) or enriched conditions. On PND 66, animals were exposed to CUS for 4 weeks. SYN and GFAP expressions were evaluated in CA1 and CA3 subfields and dentate gyrus (DG). CUS reduced the expression of SYN in all hippocampal areas, whereas lower GFAP expression was evident only in CA1 and CA3. The reduced expression of SYN in DG and CA3 was evident to male SH/CUS rats, whereas the reduced GFAP expression in CA1 and CA3 was limited to SH/CUS females. EE housing increased the hippocampal expression of both markers and protected against CUS-associated decreases. Our findings indicate that the decreases in the expression of SYN and GFAP following CUS are region and sex-specific and underline the neuroprotective role of EE against these CUS-associated changes.

Hippocampal dentate gyri proteomics reveals Wnt signaling involvement in the behavioral impairment in the THRSP-overexpressing ADHD mouse model

Children with attention-deficit/hyperactivity disorder (ADHD) often struggle with impaired executive function, temporal processing, and visuospatial memory, hallmarks of the predominantly inattentive presentation (ADHD-PI), subserved by the hippocampus. However, the specific genes/proteins involved and how they shape hippocampal structures to influence ADHD behavior remain poorly understood. As an exploratory tool, hippocampal dentate gyri tissues from thyroid hormone-responsive protein overexpressing (THRSP OE) mice with defining characteristics of ADHD-PI were utilized in proteomics. Integrated proteomics and network analysis revealed an altered protein network involved in Wnt signaling. Compared with THRSP knockout (KO) mice, THRSP OE mice showed impaired attention and memory, accompanied by dysregulated Wnt signaling affecting hippocampal dentate gyrus cell proliferation and expression of markers for neural stem cell (NSC) activity. Also, combined exposure to an enriched environment and treadmill exercise could improve behavioral deficits in THRSP OE mice and Wnt signaling and NSC activity. These findings show new markers specific to the ADHD-PI presentation, converging with the ancient and evolutionary Wnt signaling pathways crucial for cell fate determination, migration, polarity, and neural patterning during neurodevelopment. These findings from THRSP OE mice support the role of Wnt signaling in neurological disorders, particularly ADHD-PI presentation.

Exposure to static magnetic field facilitates selective attention and neuroplasticity in rats

Static magnetic fields (SMF) have neuroprotective and behavioral effects in rats, however, little is known about the effects of SMF on cognition, motor function and the underlying neurochemical mechanisms. In this study, we focused on the effects of short-term (5~10d) and long-term (13~38d) SMF exposure on selective attention and motor coordination of rats, as well as associated alterations in expression level of neuroplasticity-related structural proteins and cryptochrome (CRY1) protein in the cortex, striatum and ventral midbrain. The results showed that 6 d SMF exposure significantly enhanced selective attention without affecting locomotor activity in open field. All SMF exposures non-significantly enhanced motor coordination (Rotarod test). Neurochemical analysis demonstrated that 5d SMF exposure increased the expression of cortical and striatal CRY1 and synapsin-1 (SYN1), striatal total synapsins (SYN), and synaptophysin (SYP), growth associated protein-43 (GAP43) and post-synaptic density protein-95 (PSD95) in the ventral midbrain. Exposure to SMF for 14d increased PSD95 level in the ventral midbrain while longer SMF exposure elevated the levels of PSD95 in the cortex, SYN and SYN1 in all the examined brain areas. The increased expression of cortical and striatal CRY1and SYN1 correlated with the short-lasting effect of SMF on improving selective attention. Collectively, SMF's effect on selective attention attenuated following longer exposure to SMF whereas its effects on neuroplasticity-related structural biomarkers were time- and brain area-dependent, with some protein levels increasing with longer time exposure. These findings suggest a potential use of SMF for treatment of neurological diseases in which selective attention or neuroplasticity is impaired.

The role of enriched environment in neural development and repair

In addition to genetic information, environmental factors play an important role in the structure and function of nervous system and the occurrence and development of some nervous system diseases. Enriched environment (EE) can not only promote normal neural development through enhancing neuroplasticity but also play a nerve repair role in restoring functional activities during CNS injury by morphological and cellular and molecular adaptations in the brain. Different stages of development after birth respond to the environment to varying degrees. Therefore, we systematically review the pro-developmental and anti-stress value of EE during pregnancy, pre-weaning, and “adolescence” and analyze the difference in the effects of EE and its sub-components, especially with physical exercise. In our exploration of potential mechanisms that promote neurodevelopment, we have found that not all sub-components exert maximum value throughout the developmental phase, such as animals that do not respond to physical activity before weaning, and that EE is not superior to its sub-components in all respects. EE affects the developing and adult brain, resulting in some neuroplastic changes in the microscopic and macroscopic anatomy, finally contributing to enhanced learning and memory capacity. These positive promoting influences are particularly prominent regarding neural repair after neurobiological disorders. Taking cerebral ischemia as an example, we analyzed the molecular mediators of EE promoting repair from various dimensions. We found that EE does not always lead to positive effects on nerve repair, such as infarct size. In view of the classic issues such as standardization and relativity of EE have been thoroughly discussed, we finally focus on analyzing the essentiality of the time window of EE action and clinical translation in order to devote to the future research direction of EE and rapid and reasonable clinical application.

Environmental Enrichment Mitigates the Long-Lasting Sequelae of Perinatal Fentanyl Exposure in Mice

The opioid epidemic is a rapidly evolving societal issue driven, in part, by a surge in synthetic opioid use. A rise in fentanyl use among pregnant women has led to a 40-fold increase in the number of perinatally-exposed infants in the past decade. These children are more likely to develop mood-related and somatosensory-related conditions later in life, suggesting that fentanyl may permanently alter neural development. Here, we examined the behavioral and synaptic consequences of perinatal fentanyl exposure in adolescent male and female C57BL/6J mice and assessed the therapeutic potential of environmental enrichment to mitigate these effects. Dams were given ad libitum access to fentanyl (10 µg/ml, per os) across pregnancy and until weaning [postnatal day (PD)21]. Perinatally-exposed adolescent mice displayed hyperactivity (PD45), enhanced sensitivity to anxiogenic environments (PD46), and sensory maladaptation (PD47), sustained behavioral effects that were completely normalized by environmental enrichment (PD21-PD45). Additionally, environmental enrichment normalized the fentanyl-induced changes in the frequency of miniature EPSCs (mEPSCs) of layer 2/3 neurons in the primary somatosensory cortex (S1). We also demonstrate that fentanyl impairs short-term potentiation (STP) and long-term potentiation (LTP) in S1 layer 2/3 neurons, which, instead, exhibit a sustained depression of synaptic transmission that is restored by environmental enrichment. On its own, environmental enrichment suppressed long-term depression (LTD) of control S1 neurons from vehicle-treated mice subjected to standard housing conditions. These results demonstrate that the lasting effects of fentanyl can be ameliorated with a noninvasive intervention introduced during early development.SIGNIFICANCE STATEMENT Illicit use of fentanyl accounts for a large proportion of opioid-related overdose deaths. Children exposed to opioids during development have a higher risk of developing neuropsychiatric disorders later in life. Here, we employ a preclinical model of perinatal fentanyl exposure that recapitulates these long-term impairments and show, for the first time, that environmental enrichment can reverse deficits in somatosensory circuit function and behavior. These findings have the potential to directly inform and guide ongoing efforts to mitigate the consequences of perinatal opioid exposure.

Enriched Environment and Exercise Enhance Stem Cell Therapy for Stroke, Parkinson’s Disease, and Huntington’s Disease

Stem cells, specifically embryonic stem cells (ESCs), mesenchymal stem cells (MSCs), induced pluripotent stem cells (IPSCs), and neural progenitor stem cells (NSCs), are a possible treatment for stroke, Parkinson’s disease (PD), and Huntington’s disease (HD). Current preclinical data suggest stem cell transplantation is a potential treatment for these chronic conditions that lack effective long-term treatment options. Finding treatments with a wider therapeutic window and harnessing a disease-modifying approach will likely improve clinical outcomes. The overarching concept of stem cell therapy entails the use of immature cells, while key in recapitulating brain development and presents the challenge of young grafted cells forming neural circuitry with the mature host brain cells. To this end, exploring strategies designed to nurture graft-host integration will likely enhance the reconstruction of the elusive neural circuitry. Enriched environment (EE) and exercise facilitate stem cell graft-host reconstruction of neural circuitry. It may involve at least a two-pronged mechanism whereby EE and exercise create a conducive microenvironment in the host brain, allowing the newly transplanted cells to survive, proliferate, and differentiate into neural cells; vice versa, EE and exercise may also train the transplanted immature cells to learn the neurochemical, physiological, and anatomical signals in the brain towards better functional graft-host connectivity.