Environmental enrichment modulates inflammation during development in long-evans rats (Rattus norvegicus)

Reduction of restricted repetitive behavior by environmental enrichment: Potential neurobiological mechanisms

Restricted repetitive behaviors (RRB) are one of two diagnostic criteria for autism spectrum disorder and common in other neurodevelopmental and psychiatric disorders. The term restricted repetitive behavior refers to a wide variety of inflexible patterns of behavior including stereotypy, self-injury, restricted interests, insistence on sameness, and ritualistic and compulsive behavior. However, despite their prevalence in clinical populations, their underlying causes remain poorly understood hampering the development of effective treatments. Intriguingly, numerous animal studies have demonstrated that these behaviors are reduced by rearing in enriched environments (EE). Understanding the processes responsible for the attenuation of repetitive behaviors by EE should offer insights into potential therapeutic approaches, as well as shed light on the underlying neurobiology of repetitive behaviors. This review summarizes the current knowledge of the relationship between EE and RRB and discusses potential mechanisms for EE's attenuation of RRB based on the broader EE literature. Existing gaps in the literature and future directions are also discussed.

The Impact of Hormesis, Neuronal Stress Response, and Reproduction, upon Clinical Aging: A Narrative Review

INTRODUCTION

The primary objective of researchers in the biology of aging is to gain a comprehensive understanding of the aging process while developing practical solutions that can enhance the quality of life for older individuals. This involves a continuous effort to bridge the gap between fundamental biological research and its real-world applications.

PURPOSE

In this narrative review, we attempt to link research findings concerning the hormetic relationship between neurons and germ cells, and translate these findings into clinically relevant concepts.

METHODS

We conducted a literature search using PubMed, Embase, PLOS, Digital Commons Network, Google Scholar and Cochrane Library from 2000 to 2023, analyzing studies dealing with the relationship between hormetic, cognitive, and reproductive aspects of human aging.

RESULTS

The process of hormesis serves as a bridge between the biology of neuron-germ cell interactions on one hand, and the clinical relevance of these interactions on the other. Details concerning these processes are discussed here, emphasizing new research which strengthens the overall concept.

CONCLUSIONS

This review presents a scientifically and clinically relevant argument, claiming that maintaining a cognitively active lifestyle may decrease age-related degeneration, and improve overall health in aging. This is a totally novel approach which reflects current developments in several relevant aspects of our biology, technology, and society.

Central and peripheral effects of environmental enrichment in a mouse model of arthritis

This study analyzed whether environmental enrichment (EE) modulates the nociceptive and inflammatory responses in the mouse model of arthritis induced by Complete Freund's Adjuvant (CFA). Ninety male mice (C57BL/6-JUnib, 4-weeks-old; 20-25 g) were distributed into EE and standard (SE) groups. For EE, mice were kept in bigger cages using an alternation of materials to chew (wood and paper), for nesting (cotton), to use as hiding places (plastic tunnels), and for voluntary exercise (wheel running). Arthritis was induced by an injection of CFA (50 μL) into the right hind paw or saline solution in the control group. Separate groups received the anti-inflammatory drug dexamethasone (0.5 mg/kg; every 48 h). Inflammatory and pain measurements were performed from 1 to 35 days after CFA administration. EE per se reduced the acute paw edema formation and arthritis scores. The serum levels of tumor necrosis factor (TNF) were undetectable in any experimental groups. EE diminished the immunopositivity for the microglia marker IBA1 in the pre-frontal cortex, with slight changes for hippocampal GFAP-positive activated astrocytes. Finally, EE induced a marked increment of brain-derived nerve factor (BDNF) expression in the hippocampus, an effect that was fully prevented by dexamethasone. These data bring novel evidence on the peripheral and central effects of EE in a mouse arthritis model.

Back to nature: herbal treatment, environmental enrichment, and social play can protect against unpredictable chronic stress in Long-Evans rats (Rattus norvegicus)

The importance of integrative biobehavioral responses to complex challenges cannot be overlooked. In this study, the synergetic effects of icariin (a flavonoid present in the plant Epimedium brevicornum), natural enrichment (NaEn), and play behavior were investigated. Rats (n = 60) were assigned to standard housing or NaEn; these two groups were subsequently divided into controls, rats receiving icariin treatments, and rats receiving icariin and allowed to play with an individual from another cage. All rats were exposed to unpredictable mild stressors for 4 weeks. At the end of the treatment, a Forced Swim Task (FST) was conducted to assess emotional regulation during an inescapable acute challenge. Biological samples were collected weekly and before and after the FST to monitor endocrine changes. Corticosterone (CORT), dehydroepiandrosterone (DHEA), and testosterone (T) were assayed. We found that icariin had a significant effect on DHEA/CORT ratios and T levels. NaEn also had a significant effect on both CORT and DHEA, but not on T levels. Play did not appear to be significantly related to the endocrine changes. The strongest positive effects on emotional resilience were observed in NaEn rats that also received icariin. Our results confirmed that using multiple channels to stimulate adaptive responses can be effective in increasing the ability of an organism to face uncertainty. Considering how quickly our life can change due to unpredictable events, our data is instrumental to a better comprehension of the many aspects of integrative biobehavioral responses.