Elvan Djouma

Metabotropic glutamate 5 receptors regulate sensitivity to ethanol in mice

The metabotropic glutamate receptor 5 (mGlu5) has been implicated in ethanol- and drug-seeking behaviours in rodent studies. Here we examine a number of ethanol-related behavioural assays in mice lacking mGlu5 and wild-type littermates. In a two-bottle free-choice paradigm, mGlu5-deficient mice consumed less ethanol with a reduced preference compared to wild-type mice. Indeed, mGlu5-deficienct mice were ethanol-avoiding at both concentrations of ethanol proffered (5% and 10% v/v). However, there was no difference in the rate of hepatic ethanol and acetaldehyde metabolism between genotypes and consumption of saccharin was similar. In a conditioned place preference study, mGlu5-deficient mice displayed a place preference for ethanol when conditioned with a low dose (1g/kg) of ethanol. Thus, while mGlu5-deficient mice consume less ethanol (with a reduced preference) than wild-type mice, this is not apparently related to impaired hepatic metabolism or a lack of reward from ethanol. Rather, we provide evidence that deletion of the mGlu5 receptor increases sensitivity to centrally mediated effects of ethanol.

The CRF1 receptor antagonist, antalarmin, reverses isolation-induced up-regulation of dopamine D2 receptors in the amygdala and nucleus accumbens of fawn-hooded rats.

We have previously shown that Fawn‐Hooded (FH) rats reared in isolation display an anxiety‐like phenotype and an enhanced acquisition of ethanol seeking behaviour. Furthermore, antalarmin, a selective corticotrophin‐releasing factor type 1 (CRF1) receptor antagonist, reduces isolation‐induced acquisition and maintenance of volitional ethanol consumption in this strain. The aim of this study was to investigate the ability of CRF1 receptor antagonism by antalarmin to impact upon brain chemistry in both isolated and group‐housed FH rats. To achieve this, FH rats were reared, from weaning, in either group‐housed or isolation‐housed conditions and at 12 weeks of age were treated with antalarmin (20 mg/kg, i.p; n = 10 per group) or vehicle (1 mL/kg, i.p; n = 10 per group) bi‐daily for ten consecutive days before being killed and their brains removed for neurochemical analyses. Autoradiography and in situ hybridization was employed to analyse changes in the dopaminergic and neurotrophin systems. Isolation rearing increased dopamine D2 receptor density in the central amygdala and nucleus accumbens, an effect reversed by antalarmin treatment. Conversely, treatment with antalarmin had no impact upon the isolation‐induced alterations of the mRNA encoding brain‐derived neurotrophic factor or the TrkB receptor. Collectively, these findings demonstrate that multiple signalling systems are susceptible to modulation by social isolation and that antalarmin can reverse some, but not all, isolation‐induced alterations in brain chemistry.

Depressive-like behavior and high alcohol drinking co-occur in the FH/WJD rat but appear to be under independent genetic control.

This review will consider the evidence supporting the view that a specific substrain of Fawn-Hooded rat (FH/Wjd) exhibits co-occurring depressive-like behavior and high alcohol intake independently. First, the FH/Wjd rat is compared with other Fawn-Hooded substrains (FH/Har, FHH/Eur, FHL/Eur) and it is concluded that only the FH/Wjd rat is both highly immobile in the forced swim test and drinks substantial amounts of 5-10% alcohol voluntarily. Next it is demonstrated that the FH/Wjd rat fulfils many of the criteria proposed for an animal model of alcoholism (becomes tolerant, becomes dependent and expresses withdrawal symptoms, bar-presses for alcohol). Other literature in addition to the high swim test immobility suggests that the FH/Wjd rat may also be an animal model of depression (high basal corticosterone levels, blunted hormonal responses to serotonergic agonists). To study the phenotypes more closely an inbred strain (ACI/N) of rat that drank little alcohol voluntarily and exhibited considerable swimming in the forced swim test (i.e., low immobility) was obtained. A systematic intercrossing of the parental strains and the resulting F1 progeny was carried out to generate more than 800 F2s. Swim test immobility, alcohol intake and preference and saccharin intake are four of the 7 variables assessed in each of these rats. Using classical quantitative genetics methods, it was determined that these four phenotypes exhibited modest heritability and were influenced by multiple genes. Correlation coefficients between immobility and the other measures were near zero, whereas alcohol intake and preference were highly correlated (r=0.9) and alcohol and saccharin intakes were modestly correlated (r=0.3). A final study showed that chronic fluoxetine treatment counteracted the high immobility but did not affect alcohol intake, similar to human studies. These findings suggest that although depressive-like behavior and high alcohol intake co-occur in the FH/Wjd rat, they are independently regulated.

The galanin-3 receptor antagonist, SNAP 37889, reduces operant responding for ethanol in alcohol-preferring rats.

BACKGROUND/OBJECTIVE The galanin-3 receptor (GALR3) subtype has been identified as having a role in both feeding behaviour and the regulation of emotional states including anxiety. Despite the evidence for an association between galanin and alcohol, the current study is the first to explore the direct role of GALR3 in this context. The present study investigated the potential of the novel selective GALR3 antagonist, SNAP 37889, to reduce anxiety-like behaviour and voluntary ethanol consumption in the iP (alcohol-preferring) rat. This was achieved through a number of behavioural paradigms testing for anxiety, along with the operant self-administration model. RESULTS Overall, male iP rats treated with SNAP 37889 at a dose of 30 mg/kg (i.p.) did not show altered locomotor activity or changes in anxiety-like behaviour in the elevated plus maze or light-dark paradigms. Treatment with SNAP 37889 (30 mg/kg, i.p.) reduced operant responding for solutions containing ethanol, sucrose and saccharin. Collectively, results from the current study showed that SNAP 37889 (30 mg/kg, i.p.) is effective in reducing operant responding for ethanol, independent of a sedative effect. CONCLUSIONS These findings provide evidence that GALR3 antagonism reduces alcohol consumption and further suggest that GALR3 may be implicated in the rewarding effects of natural and drug reinforcers.

An improved method to prepare an injectable microemulsion of the galanin-receptor 3 selective antagonist, SNAP 37889, using Kolliphor® HS 15

Graphical abstract

The galanin-3 receptor antagonist, SNAP 37889, suppresses alcohol drinking and morphine self-administration in mice

ABSTRACT The neuropeptide, galanin, is widely expressed in the central and peripheral nervous systems and is involved in a range of different functions including nociception, neurogenesis, hormone release, reproduction, cognitive function and appetite. Given the overlap between galanin expression and reward circuitry in the brain, galanin has been targeted for alcohol use disorder (AUD) and opioid dependency. Furthermore, the galanin‐3 receptor (GAL3) specifically regulates emotional states and plays a role in motivation, reward and drug‐seeking behaviour. We have previously shown that the GAL3 antagonist, SNAP 37889, reduces ethanol self‐administration and cue‐induced re‐instatement in alcohol‐preferring (iP) rats with no alterations in locomotor activity or anxiety‐like behaviour. The aim of this study was to investigate whether SNAP 37889 reduces binge drinking and/or self‐administration of morphine in mice. Using the Scheduled High Alcohol Consumption (SHAC) procedure, SNAP 37889 (30 mg/kg) treated mice drank significantly less ethanol, sucrose and saccharin than vehicle treated mice. Using an operant paradigm, SNAP 37889 reduced morphine self‐administration but failed to impact cue‐induced relapse‐like behaviour. SNAP 37889 had no significant effect on locomotor activity, motor co‐ordination, anxiety, nor was SNAP 37889 itself positively reinforcing. Liver assays showed that there was no alteration in the rate of hepatic ethanol metabolism between SNAP 37889 and vehicle treated mice suggesting that the reduction in ethanol intake via SNAP 37889 is due to a central effect of GAL3 signalling. This study implicates the GAL3 receptor in consummatory drive which may have wider implications for the treatment of different addictions. HIGHLIGHTSThe galanin‐3 receptor antagonist, SNAP 37889, reduces alcohol, sucrose and saccharin consumption in mice.Treatment with SNAP 37889 reduces morphine self‐administration in mice.SNAP 37889 does not affect locomotion, motor control, anxiety or conditioned place preference.

Association of Regulatory T-Cell Expansion With Progression of Amyotrophic Lateral Sclerosis: A Study of Humans and a Transgenic Mouse Model

Importance Neuroinflammation appears to be a key modulator of disease progression in amyotrophic lateral sclerosis (ALS) and thereby a promising therapeutic target. The CD4+Foxp3+ regulatory T-cells (Tregs) infiltrating into the central nervous system suppress neuroinflammation and promote the activation of neuroprotective microglia in mouse models of ALS. To our knowledge, the therapeutic association of host Treg expansion with ALS progression has not been studied in vivo. Objective To assess the role of Tregs in regulating the pathophysiology of ALS in humans and the therapeutic outcome of increasing Treg activity in a mouse model of the disease. Design, Setting, and Participants This prospective multicenter human and animal study was performed in hospitals, outpatient clinics, and research institutes. Clinical and function assessment, as well as immunological studies, were undertaken in 33 patients with sporadic ALS, and results were compared with 38 healthy control participants who were consecutively recruited from the multidisciplinary ALS clinic at Westmead Hospital between February 1, 2013, and December 31, 2014. All data analysis on patients with ALS was undertaken between January 2015 and December 2016. Subsequently, we implemented a novel approach to amplify the endogenous Treg population using peripheral injections of interleukin 2/interleukin 2 monoclonal antibody complexes (IL-2c) in transgenic mice that expressed mutant superoxide dismutase 1 (SOD1), a gene associated with motor neuron degeneration. Main Outcomes and Measures In patients with ALS, Treg levels were determined and then correlated with disease progression. Circulating T-cell populations, motor neuron size, glial cell activation, and T-cell and microglial gene expression in spinal cords were determined in SOD1G93A mice, as well as the association of Treg amplification with disease onset and survival time in mice. Results The cohort of patients with ALS included 24 male patients and 9 female patients (mean [SD] age at assessment, 58.9 [10.9] years). There was an inverse correlation between total Treg levels (including the effector CD45RO+ subset) and rate of disease progression (R = −0.40, P = .002). Expansion of the effector Treg population in the SOD1G93A mice was associated with a significant slowing of disease progression, which was accompanied by an increase in survival time (IL-2c–treated mice: mean [SD], 160.6 [10.8] days; control mice: mean [SD], 144.9 [10.6] days; P = .003). Importantly, Treg expansion was associated with preserved motor neuron soma size and marked suppression of astrocytic and microglial immunoreactivity in the spinal cords of SOD1G93A mice, as well as elevated neurotrophic factor gene expression in spinal cord and peripheral nerves. Conclusions and Relevance These findings establish a neuroprotective effect of Tregs, possibly mediated by suppression of toxic neuroinflammation in the central nervous system. Strategies aimed at enhancing the Treg population and neuroprotective activity from the periphery may prove therapeutically useful for patients with ALS.

Calorie restriction inhibits relapse behaviour and preference for alcohol within a two-bottle free choice paradigm in the alcohol preferring (iP) rat

Among its many beneficial effects, calorie restriction (CR) has also been found to reduce anxiety related behavior in the rodent. With heightened levels of stress and anxiety implicated as a key precipitating factor of relapse and alcohol addiction, it was found that a 25% CR in addition to inducing anxiolytic effects also had the capacity to reduce intake of alcohol and inhibit relapse within a model of operant self-administration. The aim of this study was to investigate if a 25% CR would also display similar effects in a two-bottle free choice paradigm, whereby 24 h ad libitum access to both 10% ethanol and water is provided. All animals were initially tested on the elevated plus maze (EPM) and open field test prior to commencing the two-bottle free choice paradigm. Differences between control and CR25% animals demonstrated the anxiolytic effects of CR, with the CR25% group displaying greater percentage of open arm/total arm duration and open arm/total arm entries in the EPM. During the acquisition phase of the two-bottle free choice paradigm, CR25% animals showed a reduced intake of 10% ethanol in ml/kg, in comparison to the control group. Whilst control animals displayed a strong preference for 10% ethanol, the CR25% group consumed both 10% ethanol and water equally with no differences found in total fluid intake between groups. Similarly this was also the case following forced deprivation. In addition to reduced intake and lack of preference for 10% ethanol, CR 25% animals unlike controls failed to display a typical alcohol deprivation effect following abstinence. Taken collectively the results of this study suggest that CR may act as a protective factor against addiction and relapse in the alcohol preferring (iP) rat. In addition, given CR25% animals did not display a preference for 10% ethanol, results also suggest that CR may be altering the hedonic impact of ethanol within this group.

Galanin Receptors as Pharmacological Targets in the Treatment of Addiction,Drug Rehabilitation, Drug Addiction Treatment,Morphine Addiction, Drug Addiction Treatment, Cocaine-Related Disorders, Cocaine Addiction, Opioid-Related Disorders, Substance-Related Disorders

Drug and alcohol abuse present an ongoing problem from both a financial and psychosocial perspective. As the worldwide prevalence of drug-abuse grows, research into the use of novel pharmacotherapies continues. Recently, the neuropeptide galanin has been implicated in the rewarding effects of addictive substances and drug-seeking behaviour. Galanin acts by binding to three receptor subtypes, which are localised within many brain regions that play a primary role in addiction. Consequently, this paper sought to review the most recent literature with particular interest in the role of galanin and its receptors in alcoholism, drug-abuse and associated mood disorders. Further, we compile the experimental findings that suggest a potential role for galanin and its three receptor subtypes in the treatment of addiction and drug-seeking behaviour. Of particular focus in this review is the large amount of experimental evidence that supports an association between the galanin-3 receptor, alcoholism and mood disorders. Ultimately, further investigation of galanin receptors as potential drug targets may contribute to the creation of new pharmacotherapies for drug dependence.

α1 adrenergic receptor agonist, phenylephrine, actively contracts early rat rib fracture callus ex vivo

Early, soft fracture callus that links fracture ends together is smooth muscle‐like in nature. We aimed to determine if early fracture callus could be induced to contract and relax ex vivo by similar pathways to smooth muscle, that is, contraction via α1 adrenergic receptor (α1AR) activation with phenylephrine (PE) and relaxation via β2 adrenergic receptor (β2AR) stimulation with terbutaline. A sensitive force transducer quantified 7 day rat rib fracture callus responses in modified Krebs–Henseliet (KH) solutions. Unfractured ribs along with 7, 14, and 21 day fracture calluses were analyzed for both α1AR and β2AR gene expression using qPCR, whilst 7 day fracture callus was examined via immunohistochemistry for both α1AR and β2AR‐ immunoreactivity. In 7 day callus, PE (10−6 M) significantly induced an increase in force that was greater than passive force generated in calcium‐free KH (n = 8, mean 51% increase, 95% CI: 26–76%). PE‐induced contractions in calluses were attenuated by the α1AR antagonist, prazosin (10−6 M; n = 7, mean 5% increase, 95% CI: 2–11%). Terbutaline did not relax callus. Gene expression of α1ARs was constant throughout fracture healing; however, β2AR expression was down‐regulated at 7 days compared to unfractured rib (p < 0.01). Furthermore, osteoprogenitor cells of early fibrous callus displayed considerable α1AR‐like immunoreactivity but not β2AR‐like immunoreactivity. Here, we demonstrate for the first time that early fracture callus can be pharmacologically induced to contract. We propose that increased concentrations of α1AR agonists such as noradrenaline may tonically contract callus in vivo to promote osteogenesis.