Increased impulsivity in rats as a result of repeated cycles of alcohol intoxication and abstinence

Purchasing Under the Influence of Alcohol: The Impact of Hazardous and Harmful Patterns of Alcohol Consumption, Impulsivity, and Compulsive Buying

The current research examined how hazardous and harmful patterns of alcohol consumption, problematic online shopping when drinking alcohol, impulsivity, and compulsive buying were associated with and predicted the frequency of making purchases while under the influence of alcohol. A sample of American adults between the ages of 25 and 64 who reported having at least one drink per week over the past 6 months were surveyed. Regression-based path modeling revealed for those who made online purchases while moderately intoxicated, hazardous and harmful patterns of drinking alcohol and, problematic online shopping when drinking alcohol, predicted the frequency of making purchases while intoxicated. For those who made online purchases while heavily intoxicated, hazardous and harmful patterns of drinking alcohol, impulsivity, problematic online shopping when drinking alcohol, and compulsive buying predicted the frequency of making purchases while intoxicated. We explain our findings by suggesting individuals engage in frequent drunk purchases because they are motivated to alleviate their negative mood states.

Aberrant glutamatergic systems underlying impulsive behaviors: Insights from clinical and preclinical research

Impulsivity is a broad construct that often refers to one of several distinct behaviors and can be measured with self-report questionnaires and behavioral paradigms. Several psychiatric conditions are characterized by one or more forms of impulsive behavior, most notably the impulsive/hyperactive subtype of attention-deficit/hyperactivity disorder (ADHD), mood disorders, and substance use disorders. Monoaminergic neurotransmitters are known to mediate impulsive behaviors and are implicated in various psychiatric conditions. However, growing evidence suggests that glutamate, the major excitatory neurotransmitter of the mammalian brain, regulates important functions that become dysregulated in conditions like ADHD. The purpose of the current review is to discuss clinical and preclinical evidence linking glutamate to separate aspects of impulsivity, specifically motor impulsivity, impulsive choice, and affective impulsivity. Hyperactive glutamatergic activity in the corticostriatal and the cerebro-cerebellar pathways are major determinants of motor impulsivity. Conversely, hypoactive glutamatergic activity in frontal cortical areas and hippocampus and hyperactive glutamatergic activity in anterior cingulate cortex and nucleus accumbens mediate impulsive choice. Affective impulsivity is controlled by similar glutamatergic dysfunction observed for motor impulsivity, except a hyperactive limbic system is also involved. Loss of glutamate homeostasis in prefrontal and nucleus accumbens may contribute to motor impulsivity/affective impulsivity and impulsive choice, respectively. These results are important as they can lead to novel treatments for those with a condition characterized by increased impulsivity that are resistant to conventional treatments.

Cognitive Dysfunction in the Addictions (CDiA): A Neuron to Neighbourhood Collaborative Research Program on Executive Dysfunction and Functional Outcomes in Outpatients Seeking Treatment for Addiction

Background

Substance use disorders (SUDs) are pressing global public health problems. Executive functions (EFs) are prominently featured in mechanistic models of addiction. However, there remain significant gaps in our understanding of EFs in SUDs, including the dimensional relationships of EFs to underlying neural circuits, molecular biomarkers, disorder heterogeneity, and functional ability. To improve health outcomes for people with SUDs, interdisciplinary clinical, preclinical and health services research is needed to inform policies and interventions aligned with biopsychosocial models of addiction. Here, we introduce Cognitive Dysfunction in the Addictions (CDiA), an integrative team-science and translational research program, which aims to fill these knowledge gaps and facilitate research discoveries to enhance treatments for people living with SUDs.

Methods

The CDiA Program comprises seven complementary interdisciplinary projects that aim to progress understanding of EF in SUDs and investigate new biological treatment approaches. The projects draw on a diverse sample of adults aged 18-60 (target N=400) seeking treatment for addiction, who are followed prospectively over one year to identify EF domains crucial to recovery. Projects 1-3 investigate SUD symptoms, brain circuits, and blood biomarkers and their associations with both EF domains (inhibition, working memory, and set-shifting) and functional outcomes (disability, quality of life). Projects 4 and 5 evaluate interventions for addiction and their impacts on EF: a clinical trial of repetitive transcranial magnetic stimulation and a preclinical study of potential new pharmacological treatments in rodents. Project 6 links EF to healthcare utilization and is supplemented with a qualitative investigation of EF-related barriers to treatment engagement for those with substance use concerns. Project 7 uses innovative whole-person modeling to integrate the multi-modal data generated across projects, applying clustering and deep learning methods to identify patient subtypes and drive future cross-disciplinary initiatives.

Discussion

The CDiA program has promise to bring scientific domains together to uncover the diverse ways in which EFs are linked to SUD severity and functional recovery. These findings, supported by emerging clinical, preclinical, health service, and whole-person modeling investigations, will facilitate future discoveries about cognitive dysfunction in addiction and could enhance the future clinical care of individuals seeking treatment for SUDs.

Engagement for alcohol escalates in the 5-choice serial reaction time task after intermittent access

Excessive intake plays a significant role in the development of alcohol use disorder and impacts 15 million Americans annually, with approximately 88 000 dying from alcohol related deaths. Several facets we contribute to alcohol use disorder include impulsivity, motivation, and attention. Previous studies have used the 5-Choice Serial Reaction Time Task (5-Choice) to analyze these types of behaviors using sugar, but recently we have published using 10% alcohol as the reward. This study analyzed 48 mice that were trained to respond for alcohol in the 5-Choice. All mice distributed and analyzed first by alcohol preference and then by consumption. Here, we became interested in a new classification called "engagement". High-engaged and low-engaged mice were determined by the number of correct responses during final Late-Stage training sessions. Interestingly, during Early-Stage training, the mice began to separate themselves into two groups based on their interaction with the task. Throughout both training stages, high-engaged mice displayed a greater number of trials and correct responses, as well as a lower percentage of omissions compared to low-engaged mice. Following three weeks of intermittent access homecage drinking, low-engaged mice showed greater increase in perseverative responding relative to high-engaged. Additionally, low-engaged mice decreased their reward and correct latencies compared to high-engaged mice suggesting an increase in motivation for alcohol. Overall, engagement analysis presents two clearly different groups, with only one being motivated to work for alcohol. These two distinct phenotypes in the 5-Choice could be used to model alcohol motivated behavior, which could help us further understand alcohol use disorder.

Engagement for Alcohol Escalates in the 5-Choice Serial Reaction Time Task After Intermittent Access

Uncontrollable binge drinking is becoming an increasingly prevalent issue in our society. This is a factor that plays a role in the development of alcohol use disorder (AUD). AUD impacts 15 million Americans annually, with approximately 88,000 dying from alcohol related deaths. There are several aspects of AUD that encourage a strong dependence on alcohol. Impulsivity, motivation, and attention are the primary behavioral facets we contribute to AUD. Many past studies have used the 5-Choice Serial Reaction Time Task (5-Choice) to analyze these types of behaviors using sugar as the reward. We have recently published a study where alcohol was used as a reward in the 5-Choice. 48 mice were trained to respond for alcohol in the 5-Choice, and the analyses for these animals were originally categorized by their alcohol preference and consumption. Upon looking at the data, we became more interested in a new way to classify these mice into groups. High engaged (HE) and low engaged (LE) mice were classified based on their number of correct responses in the last five late-stage sessions. During early-stage training, mice began to separate themselves into two groups based on their interaction with the task. The high-engaged (HE) mice were much more engaged with the task by having a high number of trials and correct responses, as well as a much lower percentage of omissions. The low engaged (LE) mice were not as engaged, this was apparent because of their lower number of trials and correct responses. They also had a much higher percentage of omissions in comparison to HE mice. LE mice presented no significant changes in late-stage training, while HE mice began responding and engaging more. These mice went through a period of intermittent access (IA), where they were allowed to drink alcohol in their cage for 3 weeks. After intermittent access, LE mice increased their responding which suggests an increase in motivation for alcohol as a reward. Engagement analysis presents two clearly different groups, one being motivated to work for alcohol and the other not wanting to work for this reward. These two distinct phenotypes in the 5-Choice could be used to model alcohol motivated behavior, which could help us further understand AUD.

Cognitive Alterations in Addictive Disorders: A Translational Approach

The cognitive decline in people with substance use disorders is well known and can be found during both the dependence and drug abstinence phases. At the clinical level, cognitive decline impairs the response to addiction treatment and increases dropout rates. It can be irreversible, even after the end of drug abuse consumption. Improving our understanding of the molecular and cellular alterations associated with cognitive decline could be essential to developing specific therapeutic strategies for its treatment. Developing animal models to simulate drug abuse-induced learning and memory alterations is critical to continue exploring this clinical situation. The main aim of this review is to summarize the most recent evidence on cognitive impairment and the associated biological markers in patients addicted to some of the most consumed drugs of abuse and in animal models simulating this clinical situation. The available information suggests the need to develop more studies to further explore the molecular alterations associated with cognitive impairment, with the ultimate goal of developing new potential therapeutic strategies.

Adaptation of the 5-choice serial reaction time task to measure engagement and motivation for alcohol in mice

Alcohol use disorder (AUD) is related to excessive binge alcohol consumption, and there is considerable interest in associated factors that promote intake. AUD has many behavioral facets that enhance inflexibility toward alcohol consumption, including impulsivity, motivation, and attention. Thus, it is important to understand how these factors might promote responding for alcohol and can change after protracted alcohol intake. Previous studies have explored such behavioral factors using responding for sugar in the 5-Choice Serial Reaction Time Task (5-CSRTT), which allows careful separation of impulsivity, attention, and motivation. Importantly, our studies uniquely focus on using alcohol as the reward throughout training and testing sessions, which is critical for beginning to answer central questions relating to behavioral engagement for alcohol. Alcohol preference and consumption in male C57BL/6 mice were determined from the first 9 sessions of 2-h alcohol drinking which were interspersed among 5-CSRTT training. Interestingly, alcohol preference but not consumption level significantly predicted 5-CSRTT responding for alcohol. In contrast, responding for strawberry milk was not related to alcohol preference. Moreover, high-preference (HP) mice made more correct alcohol-directed responses than low-preference (LP) during the first half of each session and had more longer reward latencies in the second half, with no differences when performing for strawberry milk, suggesting that HP motivation for alcohol may reflect “front-loading.” Mice were then exposed to an Intermittent Access to alcohol paradigm and retested in 5-CSRTT. While both HP and LP mice increased 5-CSRTT responding for alcohol, but not strawberry milk, LP performance rose to HP levels, with a greater change in correct and premature responding in LP versus HP. Overall, this study provides three significant findings: (1) alcohol was a suitable reward in the 5-CSRTT, allowing dissection of impulsivity, attention, and motivation in relation to alcohol drinking, (2) alcohol preference was a more sensitive indicator of mouse 5-CSRTT performance than consumption, and (3) intermittent alcohol drinking promoted behavioral engagement with alcohol, especially for individuals with less initial engagement.

The effects of acamprosate on prefrontal cortical function are mimicked by CaCl2 and they are influenced by the history of alcohol exposure

Alcohol use disorder is associated with functional changes in the medial prefrontal cortex (mPFC), which include altered glutamatergic transmission and deficits in executive functions that contribute to relapse. Acamprosate (calcium-bis N-acetylhomotaurinate) reduces alcohol craving and relapse, effects that are thought to be mediated by acamprosate's ability to ameliorate alcohol-induced dysregulation of glutamatergic signaling. Treatment with acamprosate and its active moiety calcium (CaCl2) both improve deficits in cognitive flexibility in postdependent mice following chronic intermittent ethanol (CIE) exposure. Here, we show that mice that self-administered alcohol under goal-directed conditions (i.e., operant responding on a fixed-ratio schedule) also display similar deficits in cognitive flexibility and altered glutamatergic signaling in the mPFC, both of which were improved with acamprosate or CaCl2. However, under conditions shown to bias behavior towards habitual responding (operant self-administration after CIE exposure, or on a variable interval schedule), alcohol-induced changes to glutamatergic transmission were unaffected by either acamprosate or CaCl2 treatment. Together, these findings suggest that the variable effects of acamprosate on synaptic signaling may reflect a shift in mPFC networks related to the loss of behavioral control in habitual alcohol-seeking.

Maternal Separation Alters Ethanol Drinking and Reversal Learning Processes in Adolescent Rats: The Impact of Sex and Glycine Transporter Type 1 (GlyT1) Inhibitor

Adverse early life experiences are associated with an enhanced risk for mental and physical health problems, including substance abuse. Despite clinical evidence, the mechanisms underlying these relationships are not fully understood. Maternal separation (MS) is a commonly used animal model of early neglect. The aim of the current study is to determine whether the N-methyl-D-aspartate receptor (NMDAR)/glycine sites are involved in vulnerability to alcohol consumption (two-bottle choice paradigm) and reversal learning deficits (Barnes maze task) in adolescent rats subjected to the MS procedure and whether these effects are sex dependent. By using ELISA, we evaluated MS-induced changes in the NMDAR subunits (GluN1, GluN2A, GluN2B) expression, especially in the glycine-binding subunit, GluN1, in the prefrontal cortex (PFC) and ventral striatum (vSTR) of male/female rats. Next, we investigated whether Org 24598, a glycine transporter 1 (GlyT1) inhibitor, was able to modify ethanol drinking in adolescent and adult male/female rats with prior MS experience and reversal learning in the Barnes maze task. Our findings revealed that adolescent MS female rats consumed more alcohol which may be associated with a substantial increase in GluN1 subunit of NMDAR in the PFC and vSTR. Org 24598 decreased ethanol intake in both sexes with a more pronounced decrease in ethanol consumption in adolescent female rats. Furthermore, MS showed deficits in reversal learning in both sexes. Org 24598 ameliorated reversal learning deficits, and this effect was reversed by the NMDAR/glycine site inhibitor, L-701,324. Collectively, our results suggest that NMDAR/glycine sites might be targeted in the treatment of alcohol abuse in adolescents with early MS, especially females.

The role of impulsivity as predisposing behavioural trait in different aspects of alcohol self-administration in rats

BACKGROUND

Therapeutic interventions to promote abstinence and prevent relapse in alcohol use disorder (AUD) are limitedly available. Therefore, targeting risk factors in the onset and maintenance of AUD could pose an interesting alternative treatment strategy. In this regard, over the last decade trait impulsivity has received considerable attention as such a risk factor predisposing substance dependence both in clinical populations and preclinical rodent studies. This study investigated whether different forms of impulsivity (action versus choice) predict distinct stages of instrumental alcohol self-administration, extinction and cue-induced relapse.

METHODS

Two cohorts of n = 48 rats each were trained in an operant tasks for either impulsive action or impulsive choice. Subsequently, high and low impulsive rats were then tested in an alcohol self-administration and relapse model and following this retested in the impulsivity tasks to evaluate possible changes in impulsivity levels.

RESULTS

The current data show that neither impulsive action, nor impulsive choice predict the extent to which rats consume alcohol and the extent to which rats are motivated to self-administer alcohol. Moreover, extinction of responding for alcohol and cue-induced relapse was not predicted by impulsivity. Interestingly, rats and most prominently low impulsive rats became more impulsive after the alcohol self-administration procedure. Although due to employed experimental design it is not clear whether this resulted from alcohol consumption or alcohol abstinence.

CONCLUSION

Together, these findings lend further support for the notion of a unidirectional relationship between self-administration of the depressant drug alcohol and impulsivity.

Sex-dependent effects of chronic intermittent voluntary alcohol consumption on attentional, not motivational, measures during probabilistic learning and reversal

Background

Forced alcohol (ethanol, EtOH) exposure has been shown to cause significant impairments on reversal learning, a widely-used assay of cognitive flexibility, specifically on fully-predictive, deterministic versions of this task. However, previous studies have not adequately considered voluntary EtOH consumption and sex effects on probabilistic reversal learning. The present study aimed to fill this gap in the literature.

Methods

Male and female Long-Evans rats underwent either 10 weeks of voluntary intermittent 20% EtOH access or water only (H2O) access. Rats were then pretrained to initiate trials and learn stimulus-reward associations via touchscreen response, and subsequently required to select between two visual stimuli, rewarded with probability 0.70 or 0.30. In the final phase, reinforcement contingencies were reversed.

Results

We found significant sex differences on several EtOH-drinking variables, with females reaching a higher maximum EtOH consumption, exhibiting more high-drinking days, and escalating their EtOH at a quicker rate compared to males. During early abstinence, EtOH drinkers (and particularly EtOH-drinking females) made more initiation omissions and were slower to initiate trials than H2O drinking controls, especially during pretraining. A similar pattern in trial initiations was also observed in discrimination, but not in reversal learning. EtOH drinking rats were unaffected in their reward collection and stimulus response times, indicating intact motivation and motor responding. Although there were sex differences in discrimination and reversal phases, performance improved over time. We also observed sex-independent drinking group differences in win-stay and lose-shift strategies specific to the reversal phase.

Conclusions

Females exhibit increased vulnerability to EtOH effects in early learning: there were sex-dependent EtOH effects on attentional measures during pretraining and discrimination phases. We also found sex-independent EtOH effects on exploration strategies during reversal. Future studies should aim to uncover the neural mechanisms for changes in attention and exploration in both acute and prolonged EtOH withdrawal.

Ethanol induces maladaptive impulse control and decreased seeking behaviors in mice

Waiting impulsivity is a risk factor for many psychiatric disorders including alcohol use disorder (AUD). Highly impulsive individuals are vulnerable to alcohol abuse. However, it is not well understood whether chronic alcohol use increases the propensity for impulsive behavior. Here, we establish a novel experimental paradigm demonstrating that continuous binge-like ethanol exposure progressively leads to maladaptive impulsive behavior. To test waiting impulsivity, we employed the 5-choice serial reaction time task (5-CSRTT) in C57BL/6J male mice. We assessed premature responses in the fixed and variable intertrial interval (ITI) 5-CSRTT sessions. We further characterized our ethanol-induced impulsive mice using Open Field, y-maze, two-bottle choice, and an action-outcome task. Our results indicate that continuous binge-like ethanol exposure significantly increased premature responses when mice were tested in variable ITI sessions even during a prolonged abstinent period. Ethanol-induced impulsive mice exhibited anxiety-like behavior during chronic exposures. This behavior was also observed in a separate cohort that was subjected to 20 days of abstinence. Ethanol-treated mice were less motivated for a sucrose reward compared with air-exposed control mice, while also demonstrating reduced responding during action-outcome testing. Overall, ethanol-treated mice demonstrated increased impulsive behavior, but a reduced motivation for a sucrose reward. Although waiting impulsivity has been hypothesized to be a trait or risk factor for AUD, our findings indicate that maladaptive impulse control can also be potentiated or induced by continuous chronic ethanol exposure in mice.

Concurrent Use of Alcohol and Crack Cocaine is Associated with High Levels of Anger and Liability to Aggression

Objective: To evaluate aggressiveness in individuals receiving treatment for alcohol and crack cocaine use, both alone and in combination with one another, in order to compare them to control subjects with no history of drug problems, using the State-Trait Anger Expression Inventory. Method: The sample consisted of 67 men aged 18-65 years, divided into four groups: alcohol (n = 13); crack cocaine (n = 25); crack cocaine + alcohol (n = 16) and controls (n = 13). Participants completed the following instruments: socioeconomic questionnaire, the Wechsler Abbreviated Scale of Intelligence and the State-Trait Anger Expression Inventory. Results: Individuals with alcohol dependence alone, or comorbid with crack cocaine dependence, showed elevated levels of aggression and anger, though these varied according to the drug of abuse. Concurrent users of alcohol and crack cocaine had the highest levels of aggression, followed by isolated alcohol users, suggesting an association between alcohol consumption and aggression. Conclusion: The present findings suggest that alcohol and aggression levels may be associated with violent behavior. Concurrent use of alcohol and crack cocaine was related to higher levels of aggression, which may be associated with more severe alterations in behavior and impulse control.

Recruitment and disruption of ventral pallidal cue encoding during alcohol seeking

A critical area of inquiry in the neurobiology of alcohol abuse is the mechanism by which cues gain the ability to elicit alcohol use. Previously, we found that cue-evoked activity in rat ventral pallidum robustly encodes the value of sucrose cues trained under both Pavlovian and instrumental contingencies, despite a stronger relationship between cue-evoked activity and behavioral latency after instrumental training (Richard et al., 2018, Elife, 7, e33107). Here, we assessed: (a) ventral pallidal representations of Pavlovian versus instrumental cues trained with alcohol reward, and (b) the impact of non-associative alcohol exposure on ventral pallidal representations of sucrose cues. Decoding of cue identity based on ventral pallidum firing was blunted for the Pavlovian alcohol cue in comparison to both the instrumental cue trained with alcohol and either cue type trained with sucrose. Further, non-associative alcohol exposure had opposing effects on ventral pallidal encoding of sucrose cues trained on instrumental versus Pavlovian associations, enhancing decoding accuracy for an instrumental discriminative stimulus and reducing decoding accuracy for a Pavlovian conditioned stimulus. These findings suggest that alcohol exposure can drive biased engagement of specific reward-related signals in the ventral pallidum.

A Working Hypothesis for the Role of the Cerebellum in Impulsivity and Compulsivity

Growing evidence associates cerebellar abnormalities with several neuropsychiatric disorders in which compulsive symptomatology and impulsivity are part of the disease pattern. Symptomatology of autism, addiction, obsessive-compulsive (OCD), and attention deficit/hyperactivity (ADHD) disorders transcends the sphere of motor dysfunction and essentially entails integrative processes under control of prefrontal-thalamic-cerebellar loops. Patients with brain lesions affecting the cortico-striatum thalamic circuitry and the cerebellum indeed exhibit compulsive symptoms. Specifically, lesions of the posterior cerebellar vermis cause affective dysregulation and deficits in executive function. These deficits may be due to impairment of one of the main functions of the cerebellum, implementation of forward internal models of the environment. Actions that are independent of internal models may not be guided by predictive relationships or a mental representation of the goal. In this review article, we explain how this deficit might affect executive functions. Additionally, regionalized cerebellar lesions have been demonstrated to impair other brain functions such as the emergence of habits and behavioral inhibition, which are also altered in compulsive disorders. Similar to the infralimbic cortex, clinical studies and research in animal models suggest that the cerebellum is not required for learning goal-directed behaviors, but it is critical for habit formation. Despite this accumulating data, the role of the cerebellum in compulsive symptomatology and impulsivity is still a matter of discussion. Overall, findings point to a modulatory function of the cerebellum in terminating or initiating actions through regulation of the prefrontal cortices. Specifically, the cerebellum may be crucial for restraining ongoing actions when environmental conditions change by adjusting prefrontal activity in response to the new external and internal stimuli, thereby promoting flexible behavioral control. We elaborate on this explanatory framework and propose a working hypothesis for the involvement of the cerebellum in compulsive and impulsive endophenotypes.

Defining the place of habit in substance use disorders

It has long been suggested that alcohol or substance use disorders could emerge from the progressive development and dominance of drug habits. Like habits, drug-related behaviors are often triggered by drug-associated cues. Like habits, addictive behaviors are strong, rigid and "hard to break". Like habits, these behaviors are insensitive to their outcome and persist despite negative consequences. "Pathological habit" thus appears as a good candidate to explain the transition to compulsive drug use. However, drug use could also be considered as a goal-directed choice, driven by the expectation of drug outcomes. For example, drug addicts may engage in drug-seeking behaviors because they view the drug as more valuable than available alternatives. Substance use disorders therefore may not be all about habit, nor fully intentional, and could be considered as resulting from an imbalance between goal-directed and habitual control. The main objective of this review is to disentangle the relative contribution of habit formation and impairment of goal-directed behavior in this unbalanced control of addictive behaviors. Although deficits in goal-directed behavior have been demonstrated in alcohol and substance use disorders, reliable demonstration of abnormal habit formation has been curtailed by the paucity of paradigms designed to assess habit as a positive result. Refining our animal and human model of habit is therefore required to precisely define the place of habit in substance use disorders and develop appropriate and adapted neurobehavioral treatments.

Loren Parsons' contribution to addiction neurobiology

Loren (Larry) H. Parsons passed away at the age of 51. In spite of his premature departure, Larry much contributed to the drug abuse field. Since his graduate studies for the Ph.D. in Chemistry in J.B. Justice lab, microdialysis is the tread that links Larry's research topics, namely, the role of dopamine (DA), serotonin (5-HT), gamma-aminobutyric acid (GABA), glutamate and endocannabinoids (eCBs) in drug reinforcement and dependence. Larry was the first to show that abstinence from chronic cocaine reduces extracellular DA in the NAc, consistent with the so called 'dopamine depletion hypothesis' of cocaine addiction. Another Larry's major contributions are the studies on 5-HT and 5-HT receptors' role in cocaine stimulant actions, which resulted in the identification of 5-HT1B receptors as a critical substrate of cocaine reinforcement. By applying mass spectrometry to eCBs analysis in brain dialysates, Larry's lab showed that ethanol, heroin, nicotine and cocaine differentially affect anandamide and 2-arachidonoylglicerol overflow in the NAc shell, a critical site of drugs of abuse DA stimulant actions. Larry also applied microdialysis to study GABA and glutamate's role in ethanol dependence and heroin reinforcement, providing in vivo evidence for a sensitization of corticotropin-releasing factor-dependent release of GABA in the central amygdala in withdrawal from chronic ethanol and for a reduction of GABA transmission in the ventral pallidum in heroin but not cocaine intravenous self-administration. Larry showed the wide possibilities of microdialysis as a general purpose methodology for monitoring neurotransmitters and neuromodulators in the brain extracellular compartment. From this viewpoint, he stands as the best advocate for microdialysis.

Facets of impulsivity and alcohol use: What role do emotions play?

Alcohol misuse is a major public concern. Impulsivity has been recognised as a significant risk factor predisposing for the initiation of alcohol use, continuation and excessive alcohol use. Evidence suggests that impulsivity is also a result of both acute alcohol intoxication and long-term alcohol abuse. The multifaceted character of impulsivity and the various ways of assessing it in humans and animal models, hampers the full understanding of how impulsivity relates to alcohol use and misuse. Therefore, in this review we evaluate recent developments in the field, trying to disentangle the contribution of different impulsivity subtypes as causes and effects of alcohol use. Moreover, we review a growing body of evidence, including brain imaging, suggesting the importance of emotional states in engaging in alcohol consumption, particularly in highly impulsive individuals. We also present recent insights into how emotional processing is manifested in alcoholism and binge drinking and suggest novel approaches to treatment and prevention opportunities which target emotional-regulation as well as emotional perception and insight.

Operant over-responding is more sensitive than reversal learning for revealing behavioral changes after withdrawal from alcohol consumption

In humans, prior alcohol use is linked with impulsivity and impaired decision-making, but the nature of this relationship is unclear. In a previous study in rats, we found that prior alcohol access led to over-responding in go/no-go discrimination training, but had no effect on discrimination learning. It was unclear whether this over-responding effect would occur in a reversal learning task, or whether prior alcohol would impair reversal learning in our task. In the present experiments, we determined whether six weeks of chronic intermittent alcohol access would induce over-responding or impair reversal learning in our task. Our task allowed for multiple responses/trial with limited reinforcement, so over-responding could be assessed. In Exp. 1, we gave three days of discrimination training prior to access to 20% alcohol or water, then reversed task contingencies starting 4 days after the end of alcohol access. In Exp. 2, we gave either three or six days of discrimination training prior to the same alcohol access and reversal learning procedures to determine if the original training length would affect alcohol's behavioral effects. We found no reversal learning deficits in either experiment. Across both experiments, we found that the Alcohol group exhibited over-responding to the active lever, but this effect was smaller than in our previous discrimination experiments. Our data suggest that there are behavioral changes after voluntary alcohol access that can be missed by some discrimination/reversal learning assessments, and our over-responding task can detect these transient changes. However, over-responding is more pronounced in discrimination than reversal learning.

Phosphorylation of calcium/calmodulin-dependent protein kinase II in the rat dorsal medial prefrontal cortex is associated with alcohol-induced cognitive inflexibility

Repeated cycles of alcohol [ethanol (EtOH)] intoxication and withdrawal dysregulate excitatory glutamatergic systems in the brain and induce neuroadaptations in the medial prefrontal cortex (mPFC) that contribute to cognitive dysfunction. The mPFC is composed of subdivisions that are functionally distinct, with dorsal regions facilitating drug-cue associations and ventral regions modulating new learning in the absence of drug. A key modulator of glutamatergic activity is the holoenzyme calcium/calmodulin-dependent protein kinase II (CaMKII) that phosphorylates ionotropic glutamate receptors. Here, we examined the hypothesis that abstinence from chronic intermittent EtOH (CIE) exposure dysregulates CaMKII activity in the mPFC to impair cognitive flexibility. We used an operant model of strategy set shifting in male Long-Evans rats demonstrating reduced susceptibility to trial omissions during performance in a visual cue-guided task versus albino strains. Relative to naïve controls, rats experiencing approximately 10 days of abstinence from CIE vapor exposure demonstrated impaired performance during a procedural shift from visual cue to spatial location discrimination. Phosphorylation of CaMKII subtype α was upregulated in the dorsal, but not ventral mPFC of CIE-exposed rats, and was positively correlated with perseverative-like responding during the set shift. The findings suggest that abstinence from CIE exposure induces an undercurrent of kinase activity (e.g. CaMKII), which may promote aberrant glutamatergic responses in select regions of the mPFC. Given the role of the mPFC in modulating executive control of behavior, we propose that increased CaMKII subtype α activity reflects a dysregulated 'top-down' circuit that interferes with adaptive behavioral performance under changing environmental demands.

Ethanol Reinforcement Elicits Novel Response Inhibition Behavior in a Rat Model of Ethanol Dependence

Lower impulse control is a known risk factor for drug abuse vulnerability. Chronic experience with illicit drugs is suggested to enhance impulsivity and thereby perpetuate addiction. However, the nature of this relationship (directionality, causality) with regard to alcohol use disorder is unclear. The present study tested the hypothesis that higher impulsivity is observed during chronic intermittent ethanol vapor inhalation (CIE; a model of ethanol dependence) and subsequent abstinence from CIE in adult Wistar rats. Impulsivity was tested using a differential reinforcement of low rates 15 s (DRL15) schedule using either nondrug reward (palatable modified sucrose pellets) or sweetened ethanol. A decrease in the efficiency of earning reinforcers (expressed as % reinforcers/responses) is indicative of a decrease in response inhibition or an increase in impulsivity. The efficiency of reinforcement and amount of reinforcers earned were unaltered in CIE and control animals when the reinforcer was sucrose. When the reinforcer was sweetened ethanol, the efficiency of reinforcement increased in CIE rats compared with controls only during protracted abstinence. Responding for sweetened ethanol under a progressive-ratio schedule was more rapid in CIE rats during protracted abstinence. Contrary to the initial hypothesis, impulsivity did not increase in rats with a history of CIE; instead, it decreased when ethanol was used as the reinforcer. Furthermore, although the efficiency of ethanol reinforcement did not differ between CIE and control animals during CIE, CIE rats escalated the amount of sweetened ethanol consumed, suggesting that behavioral adaptations that are induced by CIE in rats that are tested under a DRL15 schedule appear to be targeted toward the maximization of ethanol intake and thus may contribute to escalation and relapse.

Adolescents show differential dysfunctions related to Alcohol and Cannabis Use Disorder severity in emotion and executive attention neuro-circuitries

Alcohol and cannabis are two substances that are commonly abused by adolescents in the United States and which, when abused, are associated with negative medical and psychiatric outcomes across the lifespan. These negative psychiatric outcomes may reflect the detrimental impact of substance abuse on neural systems mediating emotion processing and executive attention. However, work indicative of this has mostly been conducted either in animal models or adults with Alcohol and/or Cannabis Use Disorder (AUD/CUD). Little work has been conducted in adolescent patients. In this study, we used the Affective Stroop task to examine the relationship in 82 adolescents between AUD and/or CUD symptom severity and the functional integrity of neural systems mediating emotional processing and executive attention. We found that AUD symptom severity was positively related to amygdala responsiveness to emotional stimuli and negatively related to responsiveness within regions implicated in executive attention and response control (i.e., dorsolateral prefrontal cortex, anterior cingulate cortex, precuneus) as a function of task performance. In contrast, CUD symptom severity was unrelated to amygdala responsiveness but positively related to responsiveness within regions including precuneus, posterior cingulate cortex, and inferior parietal lobule as a function of task performance. These data suggest differential impacts of alcohol and cannabis abuse on the adolescent brain.

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Alcohol and cannabis are the most widely abused substances by adolescents.

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AUDIT scores are related to amygdala hyperactivity to emotional stimuli.

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AUDIT scores are related to hypoactivity in executive attention neuro-circuitry.

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CUDIT scores are related to hyperactivity in executive attention neuro-circuitry.

Morphological and functional evidence of increased excitatory signaling in the prelimbic cortex during ethanol withdrawal

Excessive alcohol consumption in humans induces deficits in decision making and emotional processing, which indicates a dysfunction of the prefrontal cortex (PFC). The present study aimed to determine the impact of chronic intermittent ethanol (CIE) inhalation on mouse medial PFC pyramidal neurons. Data were collected 6-8 days into withdrawal from 7 weeks of CIE exposure, a time point when mice exhibit behavioral symptoms of withdrawal. We found that spine maturity in prelimbic (PL) layer 2/3 neurons was increased, while dendritic spines in PL layer 5 neurons or infralimbic (IL) neurons were not affected. Corroborating these morphological observations, CIE enhanced glutamatergic transmission in PL layer 2/3 pyramidal neurons, but not IL layer 2/3 neurons. Contrary to our predictions, these cellular alterations were associated with improved, rather than impaired, performance in reversal learning and strategy switching tasks in the Barnes maze at an earlier stage of chronic ethanol exposure (5-7 days withdrawal from 3 to 4 weeks of CIE), which could result from the anxiety-like behavior associated with ethanol withdrawal. Altogether, this study adds to a growing body of literature indicating that glutamatergic activity in the PFC is upregulated following chronic ethanol exposure, and identifies PL layer 2/3 pyramidal neurons as a sensitive target of synaptic remodeling. It also indicates that the Barnes maze is not suitable to detect deficits in cognitive flexibility in CIE-withdrawn mice.

The monoamine stabilizer (-)-OSU6162 prevents the alcohol deprivation effect and improves motor impulsive behavior in rats

Alcohol craving, in combination with impaired impulse control, often leads to relapse. The dopamine system mediates the rewarding properties of alcohol but is also involved in regulating impulsive behavior. The monoamine stabilizer (−)‐OSU6162 (OSU6162) has the ability to stabilize dopamine activity depending on the prevailing dopaminergic tone and may therefore normalize the dopaminergic transmission regulating both alcohol use disorder and impulsivity. We have recently showed that OSU6162 attenuates voluntary alcohol consumption, operant alcohol self‐administration, alcohol withdrawal symptoms and cue‐induced reinstatement of alcohol seeking in rats. Here, we evaluated OSU6162's effects on motor impulsivity in Wistar rats that had voluntarily consumed alcohol or water for 10 weeks. The five‐choice serial reaction time task was used to measure motor impulsivity, and a prolonged waiting period (changed from 5 to 7 seconds) was applied to induce premature responses. OSU6162‐testing was conducted twice a week (Tuesdays and Fridays), every other week with regular baseline training sessions in between. We also tested OSU6162's effects on the alcohol deprivation effect in long‐term alcohol drinking Wistar rats. The results showed that OSU6162 (30 mg/kg) pre‐treatment significantly improved motor impulsivity in the five‐choice serial reaction time task in both alcohol and alcohol‐naïve rats. Moreover, OSU6162 (30 mg/kg) pre‐treatment prevented the alcohol deprivation effect, i.e. relapse‐like drinking behavior after a forced period of abstinence in long‐term drinking rats. In conclusion, our results provide further support for OSU6162 as a novel treatment for alcohol use disorder. The results further indicate that improvement of motor impulse control might be one mechanism behind OSU6162's ability to attenuate alcohol‐mediated behaviors.

Dysregulated Glycine Signaling Contributes to Increased Impulsivity during Protracted Alcohol Abstinence

Persons with alcoholism who are abstinent exhibit persistent impairments in the capacity for response inhibition, and this form of impulsivity is significantly associated with heightened relapse risk. Brain-imaging studies implicate aberrant prefrontal cortical function in this behavioral pathology, although the underlying mechanisms are not understood. Here we present evidence that deficient activation of glycine and serine release in the ventral medial prefrontal cortex (vmPFC) contributes to increased motor impulsivity during protracted abstinence from long-term alcohol exposure. Levels of 12 neurotransmitters were monitored in the rat vmPFC during the performance of a challenging variant of the five-choice serial reaction time task (5-CSRTT) in which alcohol-exposed rats exhibit excessive premature responding. Following long-term ethanol exposure, rats showed blunted task-related recruitment of vmPFC glycine and serine release, and the loss of an inverse relationship between levels of these neurotransmitters and premature responding normally evident in alcohol-naive subjects. Intra-vmPFC administration of the glycine transport inhibitor ALX5407 prevented excessive premature responding by alcohol-exposed rats, and this was reliant on NMDA glycine site availability. Alcohol-exposed rats and controls did not differ in their premature responding and glycine and serine levels in vmPFC during the performance of the standard 5-CSRTT. Collectively, these findings provide novel insight into cortical neurochemical mechanisms contributing to increased impulsivity following long-term alcohol exposure and highlight the NMDA receptor coagonist site as a potential therapeutic target for increased impulsivity that may contribute to relapse risk.SIGNIFICANCE STATEMENT Persons with alcoholism demonstrate increased motor impulsivity during abstinence; however, the neuronal mechanisms underlying these behavioral effects remain unknown. Here, we took advantage of an animal model that shows deficiencies in inhibitory control following prolonged alcohol exposure to investigate the neurotransmitters that are potentially responsible for dysregulated motor impulsivity following long-term alcohol exposure. We found that increased motor impulsivity is associated with reduced recruitment of glycine and serine neurotransmitters in the ventromedial prefrontal cortex (vmPFC) cortex in rats following long-term alcohol exposure. Administration of glycine transport inhibitor ALX5407 in the vmPFC alleviated deficits in impulse control.

Rat animal models for screening medications to treat alcohol use disorders

The purpose of this review is to present animal research models that can be used to screen and/or repurpose medications for the treatment of alcohol abuse and dependence. The focus will be on rats and in particular selectively bred rats. Brief introductions discuss various aspects of the clinical picture, which provide characteristics of individuals with alcohol use disorders (AUDs) to model in animals. Following this, multiple selectively bred rat lines will be described and evaluated in the context of animal models used to screen medications to treat AUDs. Next, common behavioral tests for drug efficacy will be discussed particularly as they relate to stages in the addiction cycle. Tables highlighting studies that have tested the effects of compounds using the respective techniques are included. Wherever possible the Tables are organized chronologically in ascending order to describe changes in the focus of research on AUDs over time. In general, high ethanol-consuming selectively bred rats have been used to test a wide range of compounds. Older studies usually followed neurobiological findings in the selected lines that supported an association with a propensity for high ethanol intake. Most of these tests evaluated the compound's effects on the maintenance of ethanol drinking. Very few compounds have been tested during ethanol-seeking and/or relapse and fewer still have assessed their effects during the acquisition of AUDs. Overall, while a substantial number of neurotransmitter and neuromodulatory system targets have been assessed; the roles of sex- and age-of-animal, as well as the acquisition of AUDs, ethanol-seeking and relapse continue to be factors and behaviors needing further study. This article is part of the Special Issue entitled "Alcoholism".

A schizophrenia relevant 5-Choice Serial Reaction Time Task for mice assessing broad monitoring, distractibility and impulsivity

The 5-Choice Serial Reaction Time Task (5-CSRTT) is an automated test for rodents allowing the assessment of multiple cognitive measures. Originally designed to assess cognitive deficits relevant to attention deficit hyperactivity disorder, it has been widely used in the investigation of neural systems of attention. In the current study, we have set up a modified version, which reduced the training phase to only 8-9 days with minimal food deprivation and without single-housing. Furthermore, based on evidence that patients with schizophrenia are more impaired in broad monitoring abilities than in sustained attention, we successfully developed a protocol replicating the Spatial Attentional Resource Allocation Task (SARAT), used in humans to assess broad monitoring. During this task, when the target appeared at a single pre-cued location, mice selectively responded faster. Instead, increasing the number of validly cued locations proportionately decreased accuracy. We then validated a protocol which is relevant for neuropsychiatric disorders in which additional irrelevant pre-cue lights selectively disrupted attention (distractibility). Finally, we improved previously used protocols changing inter-trial intervals from 5 to 7 s by randomly presenting this shift only in 20% of the trials. This resulted in a selective effect on premature responses (impulsivity), with important implications for schizophrenia as well as for other mental disorders. Therefore, this revised 5-CSRTT reduced training and stress on the animals while selectively measuring different cognitive functions with translational validity to schizophrenia and other psychiatric disorders.

Individual differences in voluntary alcohol intake in rats: relationship with impulsivity, decision making and Pavlovian conditioned approach

RATIONALE

Alcohol use disorder (AUD) has been associated with suboptimal decision making, exaggerated impulsivity, and aberrant responses to reward-paired cues, but the relationship between AUD and these behaviors is incompletely understood.

OBJECTIVES

This study aims to assess decision making, impulsivity, and Pavlovian-conditioned approach in rats that voluntarily consume low (LD) or high (HD) amounts of alcohol.

METHODS

LD and HD were tested in the rat gambling task (rGT) or the delayed reward task (DRT). Next, the effect of alcohol (0-1.0 g/kg) was tested in these tasks. Pavlovian-conditioned approach (PCA) was assessed both prior to and after intermittent alcohol access (IAA). Principal component analyses were performed to identify relationships between the most important behavioral parameters.

RESULTS

HD showed more optimal decision making in the rGT. In the DRT, HD transiently showed reduced impulsive choice. In both LD and HD, alcohol treatment increased optimal decision making in the rGT and increased impulsive choice in the DRT. PCA prior to and after IAA was comparable for LD and HD. When PCA was tested after IAA only, HD showed a more sign-tracking behavior. The principal component analyses indicated dimensional relationships between alcohol intake, impulsivity, and sign-tracking behavior in the PCA task after IAA.

CONCLUSIONS

HD showed a more efficient performance in the rGT and DRT. Moreover, alcohol consumption enhanced approach behavior to reward-predictive cues, but sign-tracking did not predict the level of alcohol consumption. Taken together, these findings suggest that high levels of voluntary alcohol intake are associated with enhanced cue- and reward-driven behavior.

Sensation seeking, peer deviance, and genetic influences on adolescent delinquency: Evidence for person-environment correlation and interaction

Both sensation seeking and affiliation with deviant peer groups are risk factors for delinquency in adolescence. In this study, we use a sample of adolescent twins (n = 549), 13 to 20 years old (M age = 15.8 years), in order to test the interactive effects of peer deviance and sensation seeking on delinquency in a genetically informative design. Consistent with a socialization effect, affiliation with deviant peers was associated with higher delinquency even after controlling for selection effects using a co-twin-control comparison. At the same time, there was evidence for person-environment correlation; adolescents with genetic dispositions toward higher sensation seeking were more likely to report having deviant peer groups. Genetic influences on sensation seeking substantially overlapped with genetic influences on adolescent delinquency. Finally, the environmentally mediated effect of peer deviance on adolescent delinquency was moderated by individual differences in sensation seeking. Adolescents reporting high levels of sensation seeking were more susceptible to deviant peers, a Person × Environment interaction. These results are consistent with both selection and socialization processes in adolescent peer relationships, and they highlight the role of sensation seeking as an intermediary phenotype for genetic risk for delinquency. (PsycINFO Database Record

A Genetic Animal Model of Alcoholism for Screening Medications to Treat Addiction

The purpose of this review is to present up-to-date pharmacological, genetic, and behavioral findings from the alcohol-preferring P rat and summarize similar past work. Behaviorally, the focus will be on how the P rat meets criteria put forth for a valid animal model of alcoholism with a highlight on its use as an animal model of polysubstance abuse, including alcohol, nicotine, and psychostimulants. Pharmacologically and genetically, the focus will be on the neurotransmitter and neuropeptide systems that have received the most attention: cholinergic, dopaminergic, GABAergic, glutamatergic, serotonergic, noradrenergic, corticotrophin releasing hormone, opioid, and neuropeptide Y. Herein, we sought to place the P rat's behavioral and neurochemical phenotypes, and to some extent its genotype, in the context of the clinical literature. After reviewing the findings thus far, this chapter discusses future directions for expanding the use of this genetic animal model of alcoholism to identify molecular targets for treating drug addiction in general.

Trajectories of binge drinking and personality change across emerging adulthood

College students binge drink more frequently than the broader population, yet most individuals "mature out" of binge drinking. Impulsivity and sensation seeking traits are important for understanding who is at risk for maintaining binge drinking across college and the transition to adult roles. We use latent class growth analysis (LCGA) to examine longitudinal binge-drinking trajectories spanning from the end of high school through 2 years after college (M ages = 18.4 to 23.8). Data were gathered over 10 waves from students at a large Southwestern university (N = 2,245). We use latent factor models to estimate changes in self-reported impulsive (IMP) and sensation-seeking (SS) personality traits across 2 time periods-(a) the end of high school to the end of college and (b) the 2-year transition out of college. LCGA suggested 7 binge-drinking trajectories: frequent, moderate, increasing, occasional, low increasing, decreasing, and rare. Models of personality showed that from high school through college, change in SS and IMP generally paralleled drinking trajectories, with increasing and decreasing individuals showing corresponding changes in SS. Across the transition out of college, only the increasing group demonstrated a developmentally deviant increase in IMP, whereas all other groups showed normative stability or decreases in both IMP and SS. These data indicate that "late bloomers," who begin binge drinking only in the later years of college, are a unique at-risk group for drinking associated with abnormal patterns of personality maturation during emerging adulthood. Our results indicate that personality targeted interventions may benefit college students.

Trajectories of binge drinking and personality change across emerging adulthood

College students binge drink more frequently than the broader population, yet most individuals "mature out" of binge drinking. Impulsivity and sensation seeking traits are important for understanding who is at risk for maintaining binge drinking across college and the transition to adult roles. We use latent class growth analysis (LCGA) to examine longitudinal binge-drinking trajectories spanning from the end of high school through 2 years after college (M ages = 18.4 to 23.8). Data were gathered over 10 waves from students at a large Southwestern university (N = 2,245). We use latent factor models to estimate changes in self-reported impulsive (IMP) and sensation-seeking (SS) personality traits across 2 time periods-(a) the end of high school to the end of college and (b) the 2-year transition out of college. LCGA suggested 7 binge-drinking trajectories: frequent, moderate, increasing, occasional, low increasing, decreasing, and rare. Models of personality showed that from high school through college, change in SS and IMP generally paralleled drinking trajectories, with increasing and decreasing individuals showing corresponding changes in SS. Across the transition out of college, only the increasing group demonstrated a developmentally deviant increase in IMP, whereas all other groups showed normative stability or decreases in both IMP and SS. These data indicate that "late bloomers," who begin binge drinking only in the later years of college, are a unique at-risk group for drinking associated with abnormal patterns of personality maturation during emerging adulthood. Our results indicate that personality targeted interventions may benefit college students.

Persistent effects of chronic Δ9-THC exposure on motor impulsivity in rats

RATIONALE

In humans, long-term marijuana use is associated with impaired impulse control and attentional capacity, though it has been difficult to distinguish pre-existing cognitive deficits from possible consequences of prolonged marijuana exposure.

OBJECTIVE

To evaluate the effects of long-term exposure to Δ9-Tetrahydrocannabinol (Δ9-THC), the primary psychoactive constituent in marijuana, on indices of impulse control and attentional capacity using the rat 5-Choice Serial Reaction Time Task (5-CSRTT).

METHODS

Ten 14-day cycles of Δ9-THC dosing and 5-CSRTT testing were employed, each comprised of 5-day Δ9-THC dosing (0.3 or 3 mg/kg b.i.d.) and 5-CSRTT testing during the 9 days of drug abstinence. Subsequent 5-CSRTT testing continued during 5 weeks of protracted abstinence.

RESULTS

Dose-dependent increases in motor impulsivity (premature responses) and behavioral disinhibition (perseverative responses) emerged following 5 cycles of Δ9-THC exposure that persisted for the remaining dosing and testing cycles. Δ9-THC-related disruptions in motor impulsivity and behavioral inhibition were most pronounced during cognitively challenging 5-CSRTT sessions incorporating varying novel inter-trial intervals (ITIs), and these disruptions persisted for at least 5 weeks of Δ9-THC abstinence. Δ9-THC-related impairments in attentional capacity (response accuracy) were also evident during variable ITI challenge tests, though these attentional disruptions abated within 3 weeks of Δ9-THC abstinence.

CONCLUSIONS

These observations demonstrate that long-term intermittent exposure to clinically meaningful Δ9-THC doses induces persistent impairments in impulse control and attentional function. If present in humans, these disruptions may impact academic and professional performance.

Alcohol-Preferring Rats Show Goal Oriented Behaviour to Food Incentives but Are Neither Sign-Trackers Nor Impulsive

Drug addiction is often associated with impulsivity and altered behavioural responses to both primary and conditioned rewards. Here we investigated whether selectively bred alcohol-preferring (P) and alcohol-nonpreferring (NP) rats show differential levels of impulsivity and conditioned behavioural responses to food incentives. P and NP rats were assessed for impulsivity in the 5-choice serial reaction time task (5-CSRTT), a widely used translational task in humans and other animals, as well as Pavlovian conditioned approach to measure sign- and goal-tracking behaviour. Drug-naïve P and NP rats showed similar levels of impulsivity on the 5-CSRTT, assessed by the number of premature, anticipatory responses, even when the waiting interval to respond was increased. However, unlike NP rats, P rats were faster to enter the food magazine and spent more time in this area. In addition, P rats showed higher levels of goal-tracking responses than NP rats, as measured by the number of magazine nose-pokes during the presentation of a food conditioned stimulus. By contrast, NP showed higher levels of sign-tracking behaviour than P rats. Following a 4-week exposure to intermittent alcohol we confirmed that P rats had a marked preference for, and consumed more alcohol than, NP rats, but were not more impulsive when re-tested in the 5-CSRTT. These findings indicate that high alcohol preferring and drinking P rats are neither intrinsically impulsive nor do they exhibit impulsivity after exposure to alcohol. However, P rats do show increased goal-directed behaviour to food incentives and this may be associated with their strong preference for alcohol.

Altered performance in a rat gambling task after acute and repeated alcohol exposure

RATIONALE

A bidirectional relationship between alcohol use disorder (AUD) and deficits in impulse control and decision making has been suggested. However, the mechanisms by which neurocognitive impairments predispose to, or result from AUD remain incompletely understood.

OBJECTIVES

The aim of this study is to gain more insight in the effects of alcohol exposure on decision making and impulse control. We used two modified versions of the rat gambling task (rGT) that differ in the net gain and the punishment magnitude associated with the different response options.

METHODS

In experiment 1, we assessed the effects of acute alcohol treatment (0-0.8 g/kg) on rGT performance. In experiment 2, we determined the effects of alcohol on rGT acquisition (15 sessions, 0.6 g/kg). Next, these animals were challenged with alcohol (0-1.0 g/kg) prior to rGT sessions.

RESULTS

Acute alcohol treatment suppressed baseline performance in both rGT versions but only modestly altered decision making. Treatment with alcohol during acquisition increased risky choices in the rGT version that involved larger punishment and blunted the reduction in win-shift behavior during acquisition in both rGT versions. Moreover, rats treated with alcohol during acquisition showed an increase in premature and perseverative responding upon subsequent alcohol challenges (0-1.0 g/kg) and were less sensitive to the behavioral suppressant effects of alcohol.

CONCLUSIONS

Our results show that repeated alcohol exposure alters decision making during rGT acquisition and reduces the ability to adjust choice behavior on the basis of feedback. In addition, repeated alcohol exposure unmasks its behavioral disinhibitory effects in the rGT. Impaired responsiveness to choice feedback and behavioral disinhibition may contribute to the development of AUD.

Compromised frontocerebellar circuitry contributes to nonplanning impulsivity in recovering alcoholics

RATIONALE

Degradation of frontocerebellar circuitry is a principal neural mechanism of alcoholism-related executive dysfunctions affecting impulse control and cognitive planning.

OBJECTIVE

We tested the hypothesis that alcoholic patients would demonstrate compromised dorsal anterior cingulate cortex (dACC) -cerebellar functional connectivity when adjusting their strategies to accommodate uncertain conditions and would recruit compensatory brain regions to overcome ineffective response patterns.

METHODS

Twenty-six alcoholics and 26 healthy participants underwent functional MRI in two sequential runs while performing a decision-making task. The first run required a response regardless of level of ambiguity of the stimuli; the second run allowed a PASS option (i.e., no response choice), which was useful on ambiguous trials.

RESULTS

Healthy controls demonstrated strong synchronous activity between the dACC and cerebellum while planning and executing a behavioral strategy. By contrast, alcoholics showed synchronous activity between the dACC and the premotor cortex, perhaps enabling successful compensation for accuracy and reaction time in certain conditions; however, a negative outcome of this strategy was rigidity in modifying response strategy to accommodate uncertain conditions. Compared with the alcoholic group, the control group had lower nonplanning impulsiveness, which correlated with using the option PASS to respond in uncertain conditions.

CONCLUSION

These findings suggest that compromised dACC-cerebellar functional circuitry contributes to recruitment of an alternative network-dACC-premotor cortex- to perform well under low-risk, unambiguous conditions. This compensatory network, however, was inadequate to enable the alcoholics to avert making poor choices in planning and executing an effective behavioral strategy in high-risk, uncertain conditions.

Impaired response inhibition in the rat 5 choice continuous performance task during protracted abstinence from chronic alcohol consumption

Impaired cognitive processing is a hallmark of addiction. In particular, deficits in inhibitory control can propel continued drug use despite adverse consequences. Clinical evidence shows that detoxified alcoholics exhibit poor inhibitory control in the Continuous Performance Task (CPT) and related tests of motor impulsivity. Animal models may provide important insight into the neural mechanisms underlying this consequence of chronic alcohol exposure though pre-clinical investigations of behavioral inhibition during alcohol abstinence are sparse. The present study employed the rat 5 Choice-Continuous Performance Task (5C-CPT), a novel pre-clinical variant of the CPT, to evaluate attentional capacity and impulse control over the course of protracted abstinence from chronic intermittent alcohol consumption. In tests conducted with familiar 5C-CPT conditions EtOH-exposed rats exhibited impaired attentional capacity during the first hours of abstinence and impaired behavioral restraint (increased false alarms) during the first 5d of abstinence that dissipated thereafter. Subsequent tests employing visual distractors that increase the cognitive load of the task revealed significant increases in impulsive action (premature responses) at 3 and 5 weeks of abstinence, and the emergence of impaired behavioral restraint (increased false alarms) at 7 weeks of abstinence. Collectively, these findings demonstrate the emergence of increased impulsive action in alcohol-dependent rats during protracted alcohol abstinence and suggest the 5C-CPT with visual distractors may provide a viable behavioral platform for characterizing the neurobiological substrates underlying impaired behavioral inhibition resulting from chronic intermittent alcohol exposure.