Gut microbiota and voluntary alcohol consumption.

Alcohol is part of the usual diet of millions of individuals worldwide. However, not all individuals who drink alcohol experience the same effects, nor will everyone develop an alcohol use disorder. Here we propose that the intestinal microbiota (IMB) helps explain the different consumption patterns of alcohol among individuals. 507 humans participated in this study and alcohol consumption and IMB composition were analyzed. On the other hand, in 80 adult male Wistar rats, behavioral tests, alcohol intoxication, fecal transplantation, administration of antibiotics and collection of fecal samples were performed. For identification and relative quantification of bacterial taxa was used the bacterial 16 S ribosomal RNA gene. In humans, we found that heavy episodic drinking is associated with a specific stool type phenotype (type 1, according to Bristol Stool Scale; p < 0.05) and with an increase in the abundance of Actinobacteria (p < 0.05). Next, using rats, we demonstrate that the transfer of IMB from alcohol-intoxicated animals causes an increase in voluntary alcohol consumption in transplant-recipient animals (p < 0.001). The relative quantification data indicate that the genus Porphyromonas could be associated with the effect on voluntary alcohol consumption. We also show that gut microbiota depletion by antibiotics administration causes a reduction in alcohol consumption (p < 0.001) and altered the relative abundance of relevant phyla such as Firmicutes, Bacteroidetes or Cyanobacteria (p < 0.05), among others. Benjamini-Hochberg false discovery rate (FDR) correction was performed for multiple comparisons. These studies reveal some of the consequences of alcohol on the IMB and provide evidence that manipulation of IMB may alter voluntary alcohol consumption.

The influence of dopaminergic polymorphisms on selective stopping.

Although the genetic influence on global stopping has been extensively investigated, little is known about the genetic contribution to other more complex forms of inhibitory control such as selective stopping. The selectivity of inhibitory control can be assessed by using the stimulus-selective stop-signal task. Notably, recent behavioural and neural evidence indicates that individuals can adopt selective but also non-selective stopping strategies to solve it. This study aimed to investigate for the first time the influence of two relevant dopaminergic polymorphisms (in COMT and DRD2 genes) on stimulus-selective stopping in a sample of 529 adults. Results showed that although none of these polymorphisms (neither individually nor in combination) modulate the latency of the stop process in each strategy (the stop-signal reaction time), the choice of strategy was influenced by their interaction. These results suggest that dopaminergic polymorphisms might influence strategy adoption in selective stopping paradigms, which constitutes a novel finding.

Adult-onset hypothyroidism increases ethanol consumption.

RATIONALE: Only in Europe it can be estimated that more than 20 million of people would be affected by hypothyroidism in some moment of their life. Given that ethanol consumption is so frequent, it would be reasonable to ask what the consequences of ethanol consumption in those individuals affected by hypothyroidism are. OBJECTIVES: To study the interaction between hypothyroidism and ethanol consumption. METHODS: We study ethanol consumption in a rat model of methyl-mercaptoimidazole-induced-adult-onset hypothyroidism and thyroid T4/T3 hormone supplementation. Also, we studied the effects of ethanol on motor activity, memory, and anxiety. RESULTS: We found that hypothyroidism increased the voluntary ethanol consumption and that this was enhanced by thyroid hormone supplementation. Hypothyroidism was associated with motor hyperactivity which was prevented either by T4/T3 supplementation or ethanol. The relationship between hypothyroidism, ethanol, and anxiety was more complex. In an anxiogenic context, hypothyroidism and T4/T3 supplementation would increase immobility, an anxiety-like behavior, while in a less anxiogenic context would decrease rearing, a behavior related to anxiety. Regarding memory, acute ethanol administration did not alter episodic-like memory in hypothyroid rats. Gene expression of enzymes involved in the metabolism of ethanol, i.e., Adh1 and Aldh2, were altered by hypothyroidism and T4/T3 supplementation. CONCLUSIONS: Our results suggest that hypothyroid patients would need personalized attention in terms of ethanol consumption. In addition, they point that it would be useful to embrace the thyroid axis in the study of ethanol addiction, including as a possible therapeutic target for the treatment of alcoholism and its comorbid disorders.

Effects of topiramate on ethanol-cocaine interactions and DNA methyltransferase gene expression in the rat prefrontal cortex.

BACKGROUND AND PURPOSE: Recent and ongoing clinical studies have indicated that topiramate (Topamax®) could be effective in treating ethanol or cocaine abuse. However, the effects of topiramate on the co-administration of ethanol and cocaine remain largely unknown. EXPERIMENTAL APPROACH: We studied the effects of topiramate, in Wistar rats, on operant ethanol self-administration with the co-administration of cocaine (i.p.). The psychomotor effects of topiramate were examined before ethanol self-administration and cocaine exposure. Blood samples were collected to analyse ethanol and cocaine metabolism (blood ethanol levels and benzoylecgonine). Quantitative real-time PCR was used to characterize the gene expression in the prefrontal cortex. KEY RESULTS: Topiramate prevented the cocaine-induced increased response to ethanol in a dose-dependent manner without causing any motor impairment by itself. This effect was observed when topiramate was administered before ethanol access, but not when topiramate was administered before the cocaine injection. Topiramate did not block cocaine-induced psychomotor stimulation. Topiramate reduced blood ethanol levels but did not affect cocaine metabolism. Ethanol increased the gene expression of DNA methyltransferases (Dnmt1 and Dnmt3a), the corepressor Dnmt1-associated protein 1 (Dmap1), and the RNA methyltransferase Trdmt1. These effects were prevented by topiramate or cocaine. Gene expression of histone deacetylase-2 and glutamate receptor kainate-1 were only increased by cocaine treatment. Topiramate and cocaine co-administration caused an up-regulation of dopamine (Drd1, Th) and opioid (Oprm1) receptor genes. Topiramate showed a tendency to alter episodic-like memory. CONCLUSIONS AND IMPLICATIONS: Topiramate is an effective inhibitor of the cocaine-induced increase in operant ethanol self-administration.

C957T polymorphism of the dopamine D2 receptor gene is associated with motor learning and heart rate.

Genetic variants that are related to the dopaminergic system have been frequently found to be associated with various neurological and mental disorders. Here, we studied the relationships between some of these genetic variants and some cognitive and psychophysiological processes that are implicated in such disorders. Two single nucleotide polymorphisms were chosen: one in the dopamine D2 receptor gene (rs6277-C957T) and one in the catechol-O-methyltransferase gene (rs4680-Val158Met), which is involved in the metabolic degradation of dopamine. The performance of participants on two long-term memory tasks was assessed: free recall (declarative memory) and mirror drawing (procedural motor learning). Heart rate (HR) was also monitored during the initial trials of the mirror-drawing task, which is considered to be a laboratory middle-stress generator (moderate stress), and during a rest period (low stress). Data were collected from 213 healthy Caucasian university students. The C957T C homozygous participants showed more rapid learning than the T allele carriers in the procedural motor learning task and smaller differences in HR between the moderate- and the low-stress conditions. These results provide useful information regarding phenotypic variance in both healthy individuals and patients.

Additive effects of cannabinoid CB1 receptors blockade and cholecystokinin on feeding inhibition.

Cannabinoid CB1 receptor and cholecystokinin-1 (CCK(1)) receptors are located in peripheral nerve terminals of the gut, where they mediate satiety signals. Here we describe a detailed analysis of the interaction of both receptors in the control of feeding of food-deprived rats. Male Wistar rats were deprived for food 24h before testing. Rats were pre-treated with SR141716A (Rimonabant) or WIN 55,212-2 before CCK-8 sulphated administration and tested for food intake 60, 120 and 240 min after last drug injection. In parallel, the effect of Lorglumide--a CCK(1) receptor antagonist--pre-treatment was evaluated on feeding behaviour after SR141716A administration. Results show that SR141716A activates c-Fos expression in brainstem areas receiving vagal inputs. Blockade of CB1 receptors with SR141716A (1 mg/kg) reduces feeding and display additive satiety induction with the CCK(1) receptor agonist CCK-8 sulphated (5, 10, 25 µg/kg). The effect of SR141716A is not blocked by Lorglumide (10 mg/kg), indicating independent sites of action. Conversely, the administration of the CB1 agonist WIN 55,212-2 (2 mg/kg) reduced satiety induced by CCK-8. In conclusion, these results report additive anorectic actions for CCK1 activation and peripheral CB1 receptor blockade providing a framework for combined therapies in the treatment of eating disorders.

Functional interactions between endogenous cannabinoid and opioid systems: focus on alcohol, genetics and drug-addicted behaviors.

Although the first studies regarding the endogenous opioid system and addiction were published during the 1940s, addiction and cannabinoids were not addressed until the 1970s. Currently, the number of opioid addiction studies indexed in PubMed-Medline is 16 times greater than the number of cannabinoid addiction reports. More recently, functional interactions have been demonstrated between the endogenous cannabinoid and opioid systems. For example, the cannabinoid brain receptor type 1 (CB1) and mu opioid receptor type 1 (MOR1) co-localize in the same presynaptic nerve terminals and signal through a common receptor-mediated G-protein pathway. Here, we review a great variety of behavioral models of drug addiction and alcohol-related behaviors. We also include data providing clear evidence that activation of the cannabinoid and opioid endogenous systems via WIN 55,512-2 (0.4-10 mg/kg) and morphine (1.0-10 mg/kg), respectively, produces similar levels of relapse to alcohol in operant alcohol self-administration tasks. Finally, we discuss genetic studies that reveal significant associations between polymorphisms in MOR1 and CB1 receptors and drug addiction. For example, the SNP A118G, which changes the amino acid aspartate to asparagine in the MOR1 gene, is highly associated with altered opioid system function. The presence of a microsatellite polymorphism of an (AAT)n triplet near the CB1 gene is associated with drug addiction phenotypes. But, studies exploring haplotypes with regard to both systems, however, are lacking.

Dopamine transporter down-regulation following repeated cocaine: implications for 3,4-methylenedioxymethamphetamine-induced acute effects and long-term neurotoxicity in mice.

BACKGROUND AND PURPOSE: 3,4-Methylenedioxymethamphetamine (MDMA) and cocaine are two widely abused psychostimulant drugs targeting the dopamine transporter (DAT). DAT availability regulates dopamine neurotransmission and uptake of MDMA-derived neurotoxic metabolites. We aimed to determine the effect of cocaine pre-exposure on the acute and long-term effects of MDMA in mice. EXPERIMENTAL APPROACH: Mice received a course of cocaine (20 mg*kg(-1), x2 for 3 days) followed by MDMA (20 mg*kg(-1), x2, 3 h apart). Locomotor activity, extracellular dopamine levels and dopaminergic neurotoxicity were determined. Furthermore, following the course of cocaine, DAT density in striatal plasma membrane and endosome fractions was measured. KEY RESULTS: Four days after the course of cocaine, challenge with MDMA attenuated the MDMA-induced striatal dopaminergic neurotoxicity. Co-administration of the protein kinase C (PKC) inhibitor NPC 15437 prevented cocaine protection. At the same time, after the course of cocaine, DAT density was reduced in the plasma membrane and increased in the endosome fraction, and this effect was prevented by NPC 15437. The course of cocaine potentiated the MDMA-induced increase in extracellular dopamine and locomotor activity, following challenge 4 days later, compared with those pretreated with saline. CONCLUSIONS AND IMPLICATIONS: Repeated cocaine treatment followed by withdrawal protected against MDMA-induced dopaminergic neurotoxicity by internalizing DAT via a mechanism which may involve PKC. Furthermore, repeated cocaine followed by withdrawal induced behavioural and neurochemical sensitization to MDMA, measures which could be indicative of increased rewarding effects of MDMA.

Cannabinoid-induced increase in relapse-like drinking is prevented by the blockade of the glycine-binding site of N-methyl-D-aspartate receptors.

The endocannabinoid system is a neuromodulatory system which controls the release of multiple neurotransmitters, including glutamate and both, the endocannabinoid and glutamatergic systems, have been implicated in alcohol relapse. Cannabinoid agonists induce an increase in relapse-like drinking whereas glutamate receptor antagonists could prevent it. Here we hypothesize that cannabinoid-induced increases in relapse-like alcohol drinking could be mediated by glutamatergic N-methyl-d-aspartate (NMDA) receptors. To test this hypothesis, Wistar rats with a background of alcohol operant self-administration were treated with the cannabinoid receptor agonist (R)-(+)-[2,3-dihydro-5-methyl-3-(4-morpholinylmethyl), pyrrolo [1,2,3-de]-1,4-benzoxazin-6-yl]-1-naphthalenylmethanone mesylate (WIN 55.212-2, WIN) (2.0 mg/kg) during periods of alcohol deprivation. For five consecutive days, 30 min before the reintroduction of alcohol, rats were injected with the NMDA/glycine receptor antagonist 7-chloro-4-hydroxy-3-(3-phenoxy)phenylquinolin-2-[1H]-one (L-701) (1.25-5.0 mg/kg) and alcohol reinforcement was evaluated. Our results clearly show that L-701 prevented the cannabinoid-induced increase in relapse-like drinking in a dose-dependent manner, whereas L-701 alone, in the absence of WIN treatment, did not significantly alter alcohol intake. The potentiation of relapse-like drinking induced by WIN is not caused by nonspecific anxiogenic effects, since no effect was observed in the elevated-plus maze test. These alcohol-related behaviors are linked to differential changes in CNR1 and NR1 subunit mRNA transcripts. In WIN-treated rats, an increase in CNR1 transcript levels was observed in the hypothalamus and striatum, whereas in the amygdala and anterior cingulate cortex, brain regions involved in emotional processing, a decrease was observed. Interestingly, such changes were blocked after L-701 treatment. Finally, WIN treatment also caused a reduction in NR1 mRNA levels in the amygdala. In conclusion, pharmacological inactivation of the glycine-binding site of NMDA receptors may control cannabinoid-induced relapse-like drinking, which is associated with altered expression of CNR1 and NR1 gene expression as observed after WIN treatment.

Behavioural effects of quinpirole following withdrawal of chronic treatment with the CB1 agonist, HU-210, in rats.

The present study investigated spontaneous and quinpirole-induced motor responses of in rats, following withdrawal from chronic treatment with the potent cannabinoid agonist HU-210. Withdrawal from chronic HU-210 (20 microg/kg daily, 14 days) produced a decrease in spontaneous activity at 1 and 2 days and enhanced the hyperactivity induced by acute administration of the dopamine D2 agonist quinpirole (0.5 mg/kg) at 4 days after the end of HU-210 treatment. Administration of quinpirole on day 4 of withdrawal from chronic HU-210 enhanced stereotyped responses and induced jumping behaviour. These results suggest that withdrawal from chronic exposure to cannabinoid agonists could induce a time-dependent alteration in dopamine D2 psychomotor function, leading to a behavioural disorganization, comparable to acute psychotic episodes after continuous cannabinoids.

Nicotine in alcohol deprivation increases alcohol operant self-administration during reinstatement.

Tobacco and alcohol are highly co-abused by humans. Most experimental studies have evaluated ethanol consumption in animals exposed concomitantly to nicotine. However, little is known regarding the effects of nicotine administered during periods of alcohol deprivation. In the present study, adult male Wistar rats with an extended background of operant self-administration of ethanol were alcohol-deprived and treated with nicotine (0.1, 0.2, 0.4 and 0.8 mg/kg) or saline during five consecutive days in one chamber of a place conditioning apparatus. Nicotine-induced changes in locomotion were monitored daily, whereas the expression of place conditioning was studied the day after the last nicotine injection. Forty-eight hours after testing for conditioning, the animals resumed operant self-administration of ethanol and their alcohol intake was evaluated during the next 14 days. We observed that alcohol consumption was increased in animals treated with nicotine at doses of 0.2, 0.4 and 0.8 mg/kg but not in animals treated with the dose of 0.1 mg/kg or saline. Additionally, the dose of 0.8 mg/kg of nicotine not only induced persistent changes in alcohol self-administration but also produced conditioned place aversion and depressed locomotor activity. These results indicate that nicotine administration during the ethanol deprivation period can exacerbate the maintenance of alcohol consumption.