Spermidine, a positive modulator of the NMDA receptor, facilitates extinction and prevents the reinstatement of morphine-induced conditioned place preference in mice

Probiotics and the microbiota-gut-brain axis in neurodegeneration: Beneficial effects and mechanistic insights

Neurodegenerative diseases (NDs) are a group of heterogeneous disorders with a high socioeconomic burden. Although pharmacotherapy is currently the principal therapeutic approach for the management of NDs, mounting evidence supports the notion that the protracted application of available drugs would abate their dopaminergic outcomes in the long run. The therapeutic application of microbiome-based modalities has received escalating attention in biomedical works. In-depth investigations of the bidirectional communication between the microbiome in the gut and the brain offer a multitude of targets for the treatment of NDs or maximizing the patient's quality of life. Probiotic administration is a well-known microbial-oriented approach to modulate the gut microbiota and potentially influence the process of neurodegeneration. Of note, there is a strong need for further investigation to map out the mechanistic prospects for the gut-brain axis and the clinical efficacy of probiotics. In this review, we discuss the importance of microbiome modulation and hemostasis via probiotics, prebiotics, postbiotics and synbiotics in ameliorating pathological neurodegenerative events. Also, we meticulously describe the underlying mechanism of action of probiotics and their metabolites on the gut-brain axis in different NDs. We suppose that the present work will provide a functional direction for the use of probiotic-based modalities in promoting current practical treatments for the management of neurodegenerative-related diseases.

Rapastinel accelerates loss of withdrawal signs after repeated morphine and blunts relapse to conditioned place preference

The purpose of the present study was to evaluate the efficacy of rapastinel, an allosteric modulator of NMDA receptor function, to accelerate the loss of opioid withdrawal symptoms and blunt or prevent relapse to morphine conditioned place preference (CPP) in rats. Two studies were conducted. In study 1, adult and adolescent male and female rats were treated with increasing doses of morphine (5 mg/kg, bid to 25 mg/kg bid) for 5 days. On day 6 animals were treated with naloxone (1 mg/kg) and withdrawal was assessed. They were then treated with saline or rapastinel (5 mg/kg) on days 6 and 8, and withdrawal was assessed on day 9. Rapastinel treated animals exhibited significantly lower levels of withdrawal signs on day 9. No sex or age differences were observed. In Study 2, CPP for morphine was established in adult rats (males and females) by 4 daily pairings with saline and morphine (am/pm alternation). They were tested for CPP on day 5, and then treated with rapastinel (5 mg/kg) or saline daily on days 6-10 of extinction. On day 11 they received a final dose of rapastinel or saline followed by extinction trial. On day 12, animals received 1 mg/kg of morphine and were tested for relapse. Rapastinel did not affect extinction of CPP, but rapastinel-treated animals spent significantly less time in the previously morphine-paired side than saline-treated animals during the relapse trial. These findings of accelerated loss of withdrawal signs and blunted relapse to CPP suggest that rapastinel could provide an adjunctive therapy for opioid dependence during initiation of pharmacotherapy for opioid dependence.

Rewarding effect of ethanol-induced conditioned place preference in mice: Effect of the monoterpenoid linalool

Alcohol addiction is a chronic relapsing disease that is progressive and has severe detrimental health outcomes. The use of natural products has become popular for the treatment of side effects of drugs and substance abuse. Linalool is a monoterpenoid that exhibits several effects on the central nervous system. Linalool was identified to have beneficial effects on different mechanisms that are relevant in drug addiction or substance use disorder. The primary aim of the present study was to evaluate the therapeutic effect of linalool on the rewarding properties of alcohol in mice. Conditioned place preference (CPP) was established by intraperitoneal (i.p.) injection of ethanol (2 g/kg) during an 8-day conditioning trial. The effects of acamprosate and linalool on the rewarding properties of ethanol were tested in mice who received linalool (12.5, 25, and 50 mg/kg, i.p.) and acamprosate (300 mg/kg, i.p.) 30 min before each ethanol injection. CPP was extinguished by repeated testing, throughout which conditioned mice were administered daily linalool. Mice were lastly examined for reinstatement provoked by i.p. administration of single low-dose ethanol (0.4 g/kg, i.p.). Treatment with linalool reduced the acquisition and reinstatement, and precipitated the extinction of ethanol-induced CPP in mice. Acquisition and reinstatement of alcohol-induced CPP were significantly reduced by acamprosate, which also precipitated extinction. Ethanol alone and the combination with linalool or acamprosate did not alter locomotor activity. The results of this study suggest that linalool may have pharmacological effects for the treatment of alcohol addiction. In addition, further investigation is required to fully explore the benefits and possible adverse effects of linalool on alcohol addiction.

The Role of Polyamines in the Mechanisms of Cognitive Impairment

Abstract—As the population ages, age-related cognitive impairments are becoming an increasingly pressing problem. Currently, the role of polyamines (putrescine, spermidine, and spermine) in the pathogenesis of cognitive impairments of various origin is actively discussed. It was shown that the content of polyamines in the brain tissue decreases with age. Exogenous administration of polyamines makes it possible to avoid cognitive impairment and/or influence the pathogenetic processes associated with disease progression. There are 3 known ways that polyamines can enter the human body: food, synthesis by intestinal bacteria, and biosynthesis in the body. Currently, one of the most promising approaches to the prevention of cognitive impairment is the use of foods with a high content of polyamines, as well as the use of various probiotics that affect intestinal bacteria that synthesize polyamines. Since 2018, in a number of European countries projects have been launched aimed at evaluation of the impact of a diet high in polyamines on cognitive processes. The review, based on analysis of modern scientific literature and the authors' own data, presents material on the effect of polyamines on cognitive processes and the role of polyamines in the regulation of neurotransmitter processes, and discusses the role of polyamines in cognitive disorders in mental and neurological diseases.

Disrupting the Interaction of nNOS with CAPON Prevents the Reinstatement of Morphine Conditioned Place Preference

Drug abuse is a dramatic challenge for the whole society because of high relapse rate. Environmental cues are crucial for the preference memory of drug abuse. Extinction therapy has been developed to inhibit the motivational effect of drug cues to prevent the reinstatement of morphine abuse. However, extinction therapy alone only forms a new kind of unstable inhibitory memory. We found that morphine conditioned place preference (CPP) extinction training increased the association of nitric oxide synthase (nNOS) with its carboxy-terminal PDZ ligand (CAPON) in the dorsal hippocampus (dHPC) significantly and blocking the morphine-induced nNOS-CAPON association using Tat-CAPON-12C during and after extinction training reversed morphine-induced hippocampal neuroplasticity defect and prevented the reinstatement and spontaneous recovery of morphine CPP. Moreover, in the hippocampal selective ERK2 knock-out or nNOS knockout mice, the effect of Tat-CAPON-12C on the reinstatement of morphine CPP and hippocampal neuroplasticity disappeared, suggesting ERK2 is necessary for the effects of Tat-CAPON-12C. Together, our findings suggest that nNOS-CAPON interaction in the dHPC may affect the consolidation of morphine CPP extinction and dissociating nNOS-CAPON prevents the reinstatement and spontaneous recovery of morphine CPP, possibly through ERK2-mediated neuroplasticity and extinction memory consolidation, offering a new target to prevent the reinstatement of drug abuse.

Polyamines serum levels in episodic and chronic migraine

Background: Previous studies focused on food as the trigger of a migraine attack did not consider polyamines as possible activators and sensitizers of the trigeminal-vascular system through their interaction with NMDA glutamate receptors. Therefore, this study aimed to assess serum levels of nine polyamines and to evaluate their role as possible triggers and crisis maintainers in episodic and chronic migraine patients. Materials and methods: The study included 50 patients with episodic migraine (EM), 50 patients with chronic migraine (CM) and 50 healthy controls (HC). Serum levels of nine polyamines have been determined by Liquid Chromatography tandem Mass Spectrometry. Specifically, agmatine, spermidine, spermine, putrescine, cadaverine, arginine, ornithine, citrulline and lysine levels were studied. Results: Agmatine serum levels resulted reduced in EC patients with respect to CM and HC. Compared to HC subjects, serum levels of spermine and spermidine were statistically significantly increased both in CM and EM patients. Conclusions: The authors suggest that alterations of polyamines levels might contribute to the understanding of migraine external activation and help to clarify the potential role of NMDA receptor polyamines site antagonists in migraine treatment.

Spermidine, an autophagy inducer, as a therapeutic strategy in neurological disorders

Spermidine is a naturally occurring endogenous polyamine synthesized from diamine putrescine. It is a well-known autophagy inducer that maintains cellular and neuronal homeostasis. Healthy brain development and function are dependent on brain polyamine concentration. Polyamines interact with the opioid system, glutamatergic signaling and neuroinflammation in the neuronal and glial compartments. Among the polyamines, spermidine is found highest in the human brain. Age-linked fluctuations in the spermidine levels may possibly contribute to the impairments in neural network and neurogenesis. Exogenously administered spermidine helps in the treatment of brain diseases. Further, current studies highlight the ability of spermidine to promote longevity by inducing autophagy. Still, the causal neuroprotective mechanism of spermidine in neuronal dysfunction remains unidentified. This review aims to summarize various neuroprotective effects of spermidine related to anti-aging/ anti-inflammatory properties and the prevention of neurotoxicity that helps in achieving beneficial effects in age-related neurological disorder. We also expose the signaling cascades modulated by spermidine which might result in therapeutic action. The present review highlights clinical studies along with in-vivo and in-vitro preclinical studies to provide a new dimension for the therapeutic potential of spermidine in neurological disorders.