Amphetamine modifies ethanol intake of psychosocially stressed male rats

The Role of Social Stress in the Development of Inhibitory Control Deficit: A Systematic Review in Preclinical Models

Inhibitory control deficit and impulsivity and compulsivity behaviours are present in different psychopathological disorders such as addiction, obsessive-compulsive disorders and schizophrenia, among others. Social relationships in humans and animals are governed by social organization rules, which modulate inhibitory control and coping strategies against stress. Social stress is associated with compulsive alcohol and drug use, pointing towards a determining factor in an increased vulnerability to inhibitory control deficit. The goal of the present review is to assess the implication of social stress and dominance on the vulnerability to develop impulsive and/or compulsive spectrum disorders, with the aid of the information provided by animal models. A systematic search strategy was carried out on the PubMed and Web of Science databases, and the most relevant information was structured in the text and tables. A total of 34 studies were recruited in the qualitative synthesis. The results show the role of social stress and dominance in increased drug and alcohol use, aggressive and impulsive behaviour. Moreover, the revised studies support the role of Dopaminergic (DA) activity and the alterations in the dopaminergic D1/D2 receptors as key factors in the development of inhibitory control deficit by social stress.

Methamphetamine self-administration reduces alcohol consumption and preference in alcohol-preferring P rats

Subclinical levels of polysubstance use are a prevalent and understudied phenomenon. Alcohol is a substance commonly co‐used with other substances of other drug classes. These studies sought to determine the consumption effects of combining alcohol drinking and methamphetamine (MA) self‐administration. Male alcohol‐preferring P rats had continuous access to a two‐bottle alcohol drinking procedure in the home cage. Control rats remained alcohol naïve. Rats were also surgically implanted with intra‐jugular catheters and trained to self‐administer saline (control) or MA in daily 2‐hour sessions. We first measured the acquisition and maintenance of MA intake in alcohol‐consuming or control rats. MA intake was initially enhanced by alcohol consumption on a fixed ratio 1 schedule of reinforcement, but this effect did not prevail as the difficulty of the schedule (FR5 and progressive ratio) was increased. We next measured both alcohol consumption and preference before, during and after MA (or saline) self‐administration. MA self‐administration significantly reduced alcohol intake and preference ratios, a robust effect that persisted across several experimental variations. Interestingly, alcohol consumption rebounded following the cessation of MA self‐administration. The effects of MA self‐administration were specific to alcohol intake because it did not alter total fluid consumption or consumption of sucrose. MA self‐administration did not impact blood‐alcohol concentrations or alcohol‐induced loss of righting reflex suggesting no effect of MA intake on the alcohol metabolism or sensitivity. Together, the results suggest that MA intake disrupts alcohol consumption and preferences but not the reverse in alcohol‐preferring P rats.

Cluster and meta-analyses on factors influencing stress-induced alcohol drinking and relapse in rodents

Numerous preclinical studies have focused on the identification of biological and environmental factors that modulate stress and alcohol interactions. Although there is a good qualitative description of the determinants of alcohol consumption in rodents, the magnitude of the variables influencing stress-induced ethanol intake and its dynamics are still poorly understood. We therefore carried out a clustered meta-analysis on stress-induced alcohol consumption in 1520 rats. Two-step clustering of the literature-derived dataset suggests a strong dependency of the experimental outcome on the method used to measure alcohol intake. Free-choice home cage drinking versus operant self-administration is the most critical determinant of stress-induced increases in alcohol consumption in rats. Stress does not typically result in enhanced alcohol consumption in operant self-administration paradigms, whereas it leads to increased home cage drinking. Stress-induced alcohol consumption is age dependent, with adults being more sensitive than adolescents. In addition, foot shock and forced swim stress enhance alcohol intake, while restraint stress does not. In contrast, a meta-analysis of 327 rats on stress-induced reinstatement of alcohol-seeking behavior shows less influence of those modulating factors, and usually foot shock or yohimbine leads to a reinstatement of approximately 300 percent of extinction level responding. Via accurate characterization of the significant factors in the interplay of alcohol consumption, relapse and stress, our quantitative description not only improves the understanding of underlying mechanisms, but also provides an appropriate framework for the optimal experimental design of preclinical studies that more accurately translates to the human condition.