Endocannabinoid receptors contribute significantly to multiple forms of long-term depression in the rat dentate gyrus.

Cannabinoid receptors are widely expressed throughout the hippocampal formation, but are particularly dense in the dentate gyrus (DG) subregion. We, and others, have shown in mice that cannabinoid type 1 receptors (CB1Rs) are involved in a long-term depression (LTD) that can be induced by prolonged 10 Hz stimulation of the medial perforant path (MPP)-granule cell synaptic input to the DG. Here, we extend this work to examine the involvement of CB1Rs in other common forms of LTD in the hippocampus of juvenile male and female Sprague-Dawley rats (Rattus norvegicus). We found, as in mice, that prolonged 10 Hz stimulation (6000 pulses) could reliably induce a form of LTD that was dependent upon CB1R activation. In addition, we also discovered a role for both CB1R and mGluR proteins in LTD induced with 1 Hz low-frequency stimulation (1 Hz-LTD; 900 pulses) and in LTD induced by bath application of the group I mGluR agonist (RS)-3,5-Dihydroxyphenylglycine (DHPG; DHPG-LTD). This study elucidates an essential role for endocannabinoid receptors in a number of forms of LTD in the rat DG, and identifies a novel role for CB1Rs as potential therapeutic targets for conditions that involve impaired LTD in the DG.

Hippocampal cognitive impairment in juvenile rats after repeated mild traumatic brain injury.

There is growing awareness that repeated mild traumatic brain injury (r-mTBI) can cause deficits in learning and memory performance, however there is still a paucity of preclinical data identifying the extent of these deficits. Epidemiological data shows that juveniles are at high risk to sustain r-mTBI, and these injuries may cause significant changes in cognitive abilities, as they occur during a period where the brain is still maturing. This is particularly true for the hippocampus, a brain region important for learning and memory processes. R-mTBI during the juvenile period may disrupt functional capacity of the hippocampus, and thus the normal development of cognitive processes associated with this structure. To examine this issue we used a model of awake closed head injury (ACHI) and administered 8 impacts over a 4 day period to juvenile male and female rats (P25-28). A neurological assessment was preformed after each impact, and anxiety and learning related behaviours were examined 1 and 7 days after the last impact. Our results indicate that r-mTBI was associated with sensorimotor deficits in the acute phase immediately after each procedure. R-mTBI also reduced the capacity for hippocampal-dependent learning for at least 7 days post-injury, but did not result in any long-lasting changes in anxiety-related behaviours.

A Rapid Neurological Assessment Protocol for Repeated Mild Traumatic Brain Injury in Awake Rats.

Preclinical models for mild traumatic brain injury (mTBI) need to recapitulate several essential clinical features associated with mTBI, including a lack of significant neuropathology and the onset of neurocognitive symptoms normally associated with mTBI. Here we show how to establish a protocol for reliably and repeatedly inducing a mild awake closed head injury (ACHI) in rats, with no mortality or clinical indications of persistent pain. Moreover, we implement a new rapid neurological assessment protocol (NAP) that can be completely conducted within 1 min of each impact. This ACHI model will help to rectify the paucity of data on how repeated mTBI (r-mTBI) impacts the juvenile brain, an area of significant concern in clinical populations where there is evidence that behavioral sequelae following injury can be more persistent in juveniles. In addition, the ACHI model can help determine if r-mTBI early in life can predispose the brain to exhibiting greater neuropathology (i.e., chronic traumatic encephalopathy) later in life and can facilitate the identification of critical periods of vulnerability to r-mTBI across the lifespan. This article describes the protocol for administering an awake closed head mTBI (i.e., ACHI) to rats, as well as how to perform a rapid NAP following each ACHI. Methods for administering the ACHI to individual subjects repeatedly are described, as are the methods and scoring system for the NAP. The goal of this article is to provide a standardized set of procedures allowing the ACHI and NAP protocols to be used reliably by different laboratories. © 2019 by John Wiley & Sons, Inc.

Impaired Bidirectional Synaptic Plasticity in Juvenile Offspring Following Prenatal Ethanol Exposure.

BACKGROUND: The hippocampus is particularly vulnerable to the teratogenic effects of prenatal ethanol exposure (PNEE), and hippocampal structural and functional deficits are thought to contribute to the learning and memory deficits that are a hallmark feature of fetal alcohol spectrum disorders. METHODS: Sprague Dawley dams were exposed to a liquid diet that contained EtOH (35.5% EtOH-derived calories) throughout gestation, and then, PNEE juvenile (P21-28) male and female offspring were used for in vitro electrophysiological recordings. We examined long-term potentiation (LTP), long-term depression (LTD), and depotentiation in the medial perforant path input to the dentate gyrus (DG) to determine the impact of PNEE on the dynamic range of bidirectional synaptic plasticity in both sexes. RESULTS: PNEE reduced the responsiveness of the DGs of male but not in female offspring, and this effect was no longer apparent when GABAergic signaling was inhibited. There was also a sex-specific LTD impairment in males, but increasing the duration of the conditioning stimulus could overcome this deficit. The magnitude of LTP was also reduced, but in both sexes following PNEE. This appears to be an increase in the threshold for induction, not in capacity, as the level of LTP induced in PNEE animals was increased to control levels when additional conditioning stimuli were administered. CONCLUSIONS: These data are the first to describe, in a single study, the impact of PNEE on the dynamic range of bidirectional synaptic plasticity in the juvenile DG in both males and in females. The data suggest that PNEE increases the threshold for LTP in the DG in both sexes, but produces a sex-specific increase in the threshold for LTD in males These alterations reduce the dynamic range for synaptic plasticity in both sexes.

Industrial-Scale Decontamination Procedure Effects on the Content of Acaricides, Heavy Metals and Antioxidant Capacity of Beeswax.

Beeswax is useful for the beekeeping sector but also for the agro-food, pharmaceutical or cosmetics sectors. Frequently, this bee product is contaminated with pesticides reducing its utility and causing the decline in its market. This study aimed to prove the effectiveness of an industrial-scale decontamination method in removing acaricides from beeswax. Chlorfenvinphos and coumaphos decrease was higher than 90%, whereas tau fluvalinate decrease was only 30%. No changes were observed in the beeswax content of hydrocarbons and monoesters, whereas a decrease in the concentrations of Ca, Fe, Zn, Hg, Mn and P, and an increase in the concentrations of As and Si were found after the decontamination. Filtration reduced total phenolics, flavonoids and the antioxidant capacity of the lipophilic extract. These results demonstrate that the industrial method used was as effective as the method previously tested on a laboratory scale. The study also contributes to a better knowledge and characterization of beeswax, specially related to trace and ultra-trace elements and antioxidant capacity. Moreover, it offers the chance to further develop a method to effectively detect wax adulterations based on the chemical elements profile.

Beeswax by-Products Efficiently Counteract the Oxidative Damage Induced by an Oxidant Agent in Human Dermal Fibroblasts.

The antioxidant capacity and the phytochemical composition of two by-products from beeswax recycling processes were recently investigated. The aim of the present work was to evaluate the efficacy of one of these by-products, MUD1, against the oxidative stress induced by 2,2'-azobis(2-amidinopropane) dihydrochloride (AAPH) in human dermal fibroblast (HDF) cells. After a preliminary viability assay, the protective effect of MUD1 was investigated through the measurement of apoptosis level, the reactive oxygen species (ROS) and nitrite (NO2-) production, the level of protein and lipid biomarkers (carbonyl groups, total glutathione and thiobarbituric acid-reactive substance) of oxidative damage, and the measurement of antioxidant enzymes activities (glutatione peroxidase, glutathione reductase, glutathione transferase, superoxide dismutase and catalase). The obtained results showed that MUD1 exerted protective effects on HDF, increasing cell viability and counteracted the oxidative stress promoted by AAPH-treatment, and improved mitochondria functionality and wound healing capacities. This work shows the antioxidant effects exerted by beeswax by-products, demonstrating for the first time their potential against oxidative stress in human dermal fibroblast cells; however, further research will be necessary to evaluate their potentiality for human health by more deeply in vitro and in vivo studies.

Effects of Voluntary Exercise on Cell Proliferation and Neurogenesis in the Dentate Gyrus of Adult FMR1 Knockout Mice.

Fragile X syndrome (FXS) is the most common cause of inherited intellectual disability that can be traced to a single gene mutation. This disorder is caused by the hypermethylation of the Fmr1 gene, which impairs translation of Fragile X Mental Retardation Protein (FMRP). In Fmr1 knockout (KO) mice, the loss of FMRP has been shown to negatively impact adult hippocampal neurogenesis, and to contribute to learning, memory, and emotional deficits. Conversely, physical exercise has been shown to enhance cognitive performance, emotional state, and increase adult hippocampal neurogenesis. In the current experiments, we used two different voluntary running paradigms to examine how exercise impacts adult neurogenesis in the dorsal and ventral hippocampal dentate gyrus (DG) of Fmr1 KO mice. Immunohistochemical analyses showed that short-term (7 day) voluntary running enhanced cell proliferation in both wild-type (WT) and Fmr1 KO mice. In contrast, long-term (28 day) running only enhanced cell proliferation in the whole DG of WT mice, but not in Fmr1 KO mice. Interestingly, cell survival was enhanced in both WT and Fmr1 KO mice following exercise. Interestingly we found that running promoted cell proliferation and survival in the ventral DG of WTs, but promoted cell survival in the dorsal DG of Fmr1 KOs. Our data indicate that long-term exercise has differential effects on adult neurogenesis in ventral and dorsal hippocampi in Fmr1 KO mice. These results suggest that physical training can enhance hippocampal neurogenesis in the absence of FMRP, may be a potential intervention to enhance learning and memory and emotional regulation in FXS.

Are by-products from beeswax recycling process a new promising source of bioactive compounds with biomedical properties?

During the process of beeswax recycling, many industrial derivatives are obtained. These matrices may have an interesting healthy and commercial potential but to date they have not been properly studied. The aim of the present work was to evaluate the proximal and phytochemical composition, the antioxidant capacity and cytotoxic effects of two by-products from beeswax recycling process named MUD 1 and MUD 2 on liver hepatocellular carcinoma. Our results showed that MUD 1 presented the highest (P < .05) fiber, protein, carbohydrate, polyphenol and flavonoid concentration, as well as the highest (P < .05) total antioxidant capacity than the MUD 2 samples. MUD1 exerted also anticancer activity on HepG2 cells, by reducing cellular viability, increasing intracellular ROS levels and affecting mitochondrial functionality in a dose-dependent manner. We showed for the first time that by-products from beeswax recycling process can represent a rich source of phytochemicals with high total antioxidant capacity and anticancer activity; however, further researches are necessary to evaluate their potentiality for human health by in vivo studies.

Revisiting the flip side: Long-term depression of synaptic efficacy in the hippocampus.

Synaptic plasticity is widely regarded as a putative biological substrate for learning and memory processes. While both decreases and increases in synaptic strength are seen as playing a role in learning and memory, long-term depression (LTD) of synaptic efficacy has received far less attention than its counterpart long-term potentiation (LTP). Never-the-less, LTD at synapses can play an important role in increasing computational flexibility in neural networks. In addition, like learning and memory processes, the magnitude of LTD can be modulated by factors that include stress and sex hormones, neurotrophic support, learning environments, and age. Examining how these factors modulate hippocampal LTD can provide the means to better elucidate the molecular underpinnings of learning and memory processes. This is in turn will enhance our appreciation of how both increases and decreases in synaptic plasticity can play a role in different neurodevelopmental and neurodegenerative conditions.

Mild Traumatic Brain Injury Produces Long-Lasting Deficits in Synaptic Plasticity in the Female Juvenile Hippocampus.

Mild traumatic brain injury (mTBI) is becoming recognized as a significant concern in modern society. In particular, youth is being increasingly seen as a vulnerable time period for mTBI, as this is the final developmental period for the brain and typically involves robust synaptic reorganization and axonal myelination. Another issue that is being hotly debated is whether mTBI differentially impacts the male and female brain. To examine the impact of mTBI in the juvenile brain, we measured hippocampal synaptic plasticity using a closed-head mTBI model in male and female Long-Evans rats (25-28 days of age) at either 1 h, 1 day, 7 days, or 28 days post-injury. In female rats, the dentate gyrus (DG) region ipsilateral to the impact showed a significant reduction in long-term potentiation (LTP) at 1 day, which persisted to 28 days following injury. In male rats, the deficit in LTP was maximal in the CA1 and DG subfields ipsilateral to the impact site 7 days post-injury; however, these deficits did not persist to 28 days post-injury. These data indicate that mTBI can produce more immediate and persistent impairments in synaptic plasticity in the female brain.