Environmental Enrichment and Brain Neuroplasticity in the Kainate Rat Model of Temporal Lobe Epilepsy

Enriched Environment Reduces Seizure Susceptibility via Entorhinal Cortex Circuit Augmented Adult Neurogenesis

Enriched environment (EE), characterized by multi-sensory stimulation, represents a non-invasive alternative for alleviating epileptic seizures. However, the mechanism by which EE exerts its therapeutic impact remains incompletely understood. Here, it is elucidated that EE mitigates seizure susceptibility through the augmentation of adult neurogenesis within the entorhinal cortex (EC) circuit. A substantial upregulation of adult hippocampal neurogenesis concomitant with a notable reduction in seizure susceptibility has been found following exposure to EE. EE-enhanced adult-born dentate granule cells (abDGCs) are functionally activated during seizure events. Importantly, the selective activation of abDGCs mimics the anti-seizure effects observed with EE, while their inhibition negates these effects. Further, whole-brain c-Fos mapping demonstrates increased activity in DG-projecting EC CaMKIIα+ neurons in response to EE. Crucially, EC CaMKIIα+ neurons exert bidirectional modulation over the proliferation and maturation of abDGCs that can activate local GABAergic interneurons; thus, they are essential components for the anti-seizure effects mediated by EE. Collectively, this study provides compelling evidence regarding the circuit mechanisms underlying the effects of EE treatment on epileptic seizures, shedding light on the involvement of the EC-DG circuit in augmenting the functionality of abDGCs. This may help for the translational application of EE for epilepsy management.

Role of Acorus calamus in preventing depression, anxiety, and oxidative stress in long-term socially isolated rats

Background and Aim

Social isolation stress (SIS) and individual housing have been shown to cause abnormal cognitive insufficiencies, altered anxiety levels, and signs of psychiatric diseases. Acorus calamus (AC), commonly known as Sweet Flag, has been widely used in India to treat neurological, metabolic, and respiratory disorders, indicating its potential therapeutic value. This study aimed to determine the antidepressant and antioxidative effects of AC on rats subjected to long-term, social isolation-induced stress.

Materials and Methods

This study involved 2-month-old male rats (24) weighing approximately 180-200 g bred in-house. The rats were divided into four groups (n = 6): Group 1 received saline, Group 2 received SIS, Group 3 received only 50 mg/kg AC, and Group 4 received 50 mg/kg AC and SIS for 6 weeks. After this, behavioral, biochemical, and neuronal assays were conducted.

Results

Behavioral experiments showed significantly higher activity levels (p < 0.001) in AC-treated rats than in the SIS group. In addition, rats subjected to SIS with AC treatment exhibited enhanced total antioxidants, superoxide dismutase, and neuronal assays compared to rats subjected to SIS alone.

Conclusion

Acorus calamus treatment improved the antidepressant and antioxidant potential against SIS in rat brain tissue. Moreover, we proved that AC can effectively reverse the neurotoxicity induced by SIS in animal models. As we battle against the coronavirus disease 2019 pandemic and social isolation, AC could be considered a supplementary treatment to alleviate depressive-like symptoms in our present-day lifestyle.

Non-invasive sensory neuromodulation in epilepsy: Updates and future perspectives

Epilepsy, one of the most common neurological disorders, often is not well controlled by current pharmacological and surgical treatments. Sensory neuromodulation, including multi-sensory stimulation, auditory stimulation, olfactory stimulation, is a kind of novel noninvasive mind-body intervention and receives continued attention as complementary safe treatment of epilepsy. In this review, we summarize the recent advances of sensory neuromodulation, including enriched environment therapy, music therapy, olfactory therapy, other mind-body interventions, for the treatment of epilepsy based on the evidence from both clinical and preclinical studies. We also discuss their possible anti-epileptic mechanisms on neural circuit level and propose perspectives on possible research directions for future studies.

Anticonvulsant Effects of Royal Jelly in Kainic Acid-Induced Animal Model of Temporal Lobe Epilepsy Through Antioxidant Activity

Temporal lobe epilepsy (TLE) is the most common form of partial and drug-resistant epilepsy, characterized by recurrent seizures originating from temporal lobe structures like the hippocampus. Hippocampal sclerosis and oxidative stress are two important factors in the pathogenesis of TLE that exacerbate epileptic seizures in this form of epilepsy. Recently, royal jelly (RJ) shown to have neuroprotective and antioxidant activities in several neurodegenerative models. Therefore, the aim of the present study was to investigate the pretreatment effect of RJ on epileptic seizures, hippocampal neuronal loss, and oxidative stress in the rat model of kainic acid (KA)-induced TLE. To this aim, 40 male Wistar rats weighing 200-250 g were divided into 4 groups, including control, vehicle, KA, and RJ + KA. Rats received RJ (150 mg/kg/day) for 14 days before induction of TLE with KA. Epileptic behaviors were evaluated according to Racine's scale. Oxidative stress markers including, malondialdehyde (MDA), total oxidant status (TOS) and total antioxidant capacity (TAC) as well as neuronal loss in the CA1 region of the hippocampus (using Nissl staining) were evaluated in all groups. Our findings showed that RJ pretreatment significantly reduced the seizure score and increased the latency to the first seizure. RJ also reduced MDA and TOS while increasing TAC. In addition, RJ reversed neuronal damage in the hippocampal CA1 and CA3 areas. In conclusion, our results suggest that RJ has anticonvulsant and neuroprotective effects in KA induced TLE via its antioxidative properties.

Neurobehavioral effects of environmental enrichment and drug abuse vulnerability: An updated review

Environmental enrichment consisting of social peers and novel objects is known to alter neurobiological functioning and have an influence on the behavioral effects of drugs of abuse in preclinical rodent models. An earlier review from our laboratory (Stairs and Bardo, 2009) provided an overview of enrichment-specific changes in addiction-like behaviors and neurobiology. The current review updates the literature in this extensive field. Key findings from this updated review indicate that enrichment produces positive outcomes in drug abuse vulnerability beyond just psychostimulants. Additionally, recent studies indicate that enrichment activates key genes involved in cell proliferation and protein synthesis in nucleus accumbens and enhances growth factors in hippocampus and neurotransmitter signaling pathways in prefrontal cortex, amygdala, and hypothalamus. Remaining gaps in the literature and future directions for environmental enrichment and drug abuse research are identified.

Enriched environment for offspring improves learning and memory impairments induced by sevoflurane exposure during the second trimester of pregnancy

Studies in animals indicate that sevoflurane exposure in the second trimester of pregnancy has harmful effects on the learning and memory of offspring. Whether an enriched environment can reverse the damage of sevoflurane exposure in the second trimester of pregnancy on the learning and memory of rat offspring remains unclear. In this study, rats at 14 days of pregnancy were exposed to 3.5% sevoflurane for 2 hours and their offspring were treated with an enriched environment for 20 successive days. We found that the enriched environment for offspring increased nestin and Ki67 levels in hippocampal tissue, increased hippocampal neurogenesis, inhibited glycogen synthase kinase 3β activity, and increased the expression of cell proliferation-related β-catenin and apoptosis-related Bcl-2, indicating that an enriched environment reduces sevoflurane-induced damage by increasing the proliferation of stem cells in the hippocampus. These findings suggest that an enriched environment can reverse the effects of sevoflurane inhaled by rats during the second trimester of pregnancy on learning and memory of offspring. This study was approved by the Animal Ethics Committee of Shengjing Hospital of China Medical University (approval No. 2018PS07K) on January 2, 2018.

Enrichment Protocol for Rat Models

An environmental enrichment (EE) cage consisting of a broad living area and various stimulators triggers social, cognitive, and physical activities. EE has been utilized in a wide range of neurological and non-neurological studies. However, the details of the environmental enrichment protocol were not well described in these studies. This has resulted in uncertainty and inconsistency in methodology, which may thus fail to replicate environmental enrichment effects, influencing the study outcome. Here we describe the basic guidelines and present an easy-to-follow protocol for environmental enrichment in rat models. © 2021 Wiley Periodicals LLC. Basic Protocol: Environmental enrichment housing.

Impact of Stress on Epilepsy: Focus on Neuroinflammation-A Mini Review

Epilepsy, one of the most common neurological disorders worldwide, is characterized by recurrent seizures and subsequent brain damage. Despite strong evidence supporting a deleterious impact on seizure occurrence and outcome severity, stress is an overlooked component in people with epilepsy. With regard to stressor duration and timing, acute stress can be protective in epileptogenesis, while chronic stress often promotes seizure occurrence in epilepsy patients. Preclinical research suggests that chronic stress promotes neuroinflammation and leads to a depressive state. Depression is the most common psychiatric comorbidity in people with epilepsy, resulting in a poor quality of life. Here, we summarize studies investigating acute and chronic stress as a seizure trigger and an important factor that worsens epilepsy outcomes and psychiatric comorbidities. Mechanistic insight into the impact of stress on epilepsy may create a window of opportunity for future interventions targeting neuroinflammation-related disorders.

Envisioning the crosstalk between environmental enrichment and epilepsy: A novel perspective

Epilepsies are a diverse group of neurological disorders characterized by an unprovoked seizure and a brain that has an enduring predisposition to seizures. The lack of disease-modifying treatment strategies against the same has led to the exploration of novel treatment strategies that could halt epileptic seizures. In this regard, environmental enrichment (EE) has gained increased attention in recent days. EE modulates the effects of interactions between the genes and the environment on the structure and function of the brain. EE therapy can improve seizure-related symptoms in neurological diseases such as epilepsy. EE therapy can have a significant effect on cognitive disorders such as learning and memory impairments associated with seizures. EE therapy in epileptic hippocampus tissue can improve seizure-related symptoms by inducing enhanced neurogenesis and neuroprotective mechanisms. In this context, the efficiency of EE is regulated in the epilepsy by the brain-derived neurotrophic factor (BDNF)/extracellular signal-regulated kinase (ERK) signaling pathway regulated by extracellular signaling. Herein, we provide experimental evidence supporting the beneficial effects of EE in epileptic seizures and its underlying mechanism.

Environmental Complexity and Research Outcomes

Environmental complexity is an experimental paradigm as well as a potential part of animals' everyday housing experiences. In experimental uses, researchers add complexity to stimulate brain development, delay degenerative brain changes, elicit more naturalistic behaviors, and test learning and memory. Complexity can exacerbate or mitigate behavioral problems, give animals a sense of control, and allow for expression of highly driven, species-typical behaviors that can improve animal welfare. Complex environments should be designed thoughtfully with the animal's natural behaviors in mind, reported faithfully in the literature, and evaluated carefully for unexpected effects.