Recent Advances in Pharmacological Research on Alcohol

The influence of drug class on reward in substance use disorders

In the United States, the societal costs associated with drug use surpass $500 billion annually. The rewarding and reinforcing properties that drive the use of these addictive substances are typically examined concerning the neurobiological effects responsible for their abuse potential. In this review, terms such as "abuse potential," "drug," and "addictive properties" are used due to their relevance to the methodological, theoretical, and conceptual framework for understanding the phenomenon of drug-taking behavior and the associated body of preclinical and clinical literature. The use of these terms is not intended to cast aspersions on individuals with substance use disorders (SUD). Understanding what motivates substance use has been a focus of SUD research for decades. Much of this corpus of work has focused on the shared effects of each drug class to increase dopaminergic transmission within the central reward pathways of the brain, or the "reward center." However, the precise influence of each drug class on dopamine signaling, and the extent thereof, differs considerably. Furthermore, the aforementioned substances have effects on several neurobiological targets that mediate and modulate their addictive properties. The current manuscript sought to review the influence of drug class on the rewarding effects of each of the major pharmacological classes of addictive drugs (i.e., psychostimulants, opioids, nicotine, alcohol, and cannabinoids). Our review suggests that even subtle differences in drug effects can result in significant variability in the subjective experience of the drug, altering rewarding and other reinforcing effects. Additionally, this review will argue that reward (i.e., the attractive and motivational property of a stimulus) alone is not sufficient to explain the abuse liability of these substances. Instead, abuse potential is best examined as a function of both positive and negative reinforcing drug effects (i.e., stimuli that the subject will work to attain and stimuli that the subject will work to end or avoid, respectively). Though reward is central to drug use, the factors that motivate and maintain drug taking are varied and complex, with much to be elucidated.

Differences in treatment outcome between male alcohol dependent offenders of domestic violence with and without positive drug screens

Men who are violent toward their partners tend to have a dual problem with alcohol and drug use, yet little is known about differences between men with single rather than dual problems. This study was one of the first to evaluate differences between alcohol dependent men who were arrested for Intimate Partner Violence (IPV) with and without concurrent illicit drug use. Seventy-eight participants were randomly assigned to manual-guided group behavioral therapies (Cognitive Behavioral Therapy or Twelve Step Facilitation) and assessed across 12 weeks of treatment. Despite denying drug use at baseline, thirty-two clients (43%) tested positive for illicit drug use (cocaine and marijuana) during the 12 weeks of treatment. The study specifically addressed whether there were differences between clients using alcohol only versus individuals using both alcohol + drugs in terms of 1) baseline characteristics; 2) treatment compliance (e.g., attendance and substance use during treatment; and 3) treatment outcomes (alcohol, drug use, anger management, and aggression at the completion of treatment). The results showed that there were comparatively few differences between the alcohol versus the alcohol + drug using groups at baseline. Regarding treatment compliance and retention, alcohol + drug using participants attended significantly fewer sessions, had significantly fewer percent days abstinence from alcohol use, significantly more total days of positive breathalyzer results. Regarding treatment outcomes across anger management and aggression scores, the alcohol + drug using participants had significantly more impairments in anger management styles from pre- to post-treatment. However, there were no differences between the groups across verbal or physical aggression. Both groups improved in their verbal aggression from pre- to post-treatment. The findings suggest that alcohol dependent men who continue to use illicit drugs may require additional interventions to effectively control their drug use and, their anger management styles.

Ethanol modulates neuropeptide-degrading aminopeptidases at synapse level in calcium-dependent conditions

AIMS

To investigate the role of aminopeptidases in the pathways to peptides neurotransmission/neuromodulation ending in the actions of ethanol (EtOH) on the brain.

METHODS

The effects of EtOH on alanyl-, arginyl-, cystyl-, leucyl- and tyrosyl-aminopeptidase activities were studied under basal/resting and K+-stimulated conditions at the synapse level, using mouse frontal cortex synaptosomes and their incubation supernatant in a Ca2+-containing or Ca2+-free medium.

RESULTS

Under basal conditions, synaptosome aminopeptidase activities showed an inhibitory or biphasic response depending on the concentration of EtOH used and the aminopeptidase assayed, whereas supernatant activities showed a more complex response. Under K+-stimulated conditions, EtOH inhibited all synaptosome aminopeptidases assayed in presence of Ca2+. However, in absence of Ca2+, different responses were obtained depending on the concentration of EtOH used. In the supernatant, the highest concentration of EtOH inhibited the K+-stimulated increase on aminopeptidase activities, although the lowest concentration enhanced the release in presence of Ca2+. In absence of it, EtOH blocked the K+-stimulated decrease or increased the activity depending on the concentration of EtOH used.

CONCLUSIONS

The changes on aminopeptidase activities induced by EtOH may reflect the functional status of their corresponding endogenous substrates. EtOH may influence opioid peptides, oxytocin, vasopressin and the brain renin-angiotensin system through their degrading enzymes.

Low doses of alcohol have a selective effect on the recognition of happy facial expressions

Alcohol is one of the most widely used recreational drugs, yet it is associated with undesirable social behaviour. It is used primarily for its psychoactive properties, increasing sociability and talkativeness. We hypothesize that low doses of alcohol can improve the performance related to positive emotional cognition. In this experiment, we examined the effect of low doses of alcohol on the processing of emotional facial expressions. Fifteen young male volunteers drank alcohol at volumes of 30, 60, 120 ml (0.14, 0.28, 0.56 g/kg) and performed discrimination tasks on morphed facial emotion expressions of anger, happiness, sadness and surprise-neutral. One-way ANOVA co-varying pretreatment performances revealed significant differences between alcohol levels in happy face discrimination ( p<0.01). Bonferroni correction demonstrated that low doses of alcohol caused a significantly better discrimination of happy faces, and that the performances were worse with higher doses ( p<0.001). No significance was observed with the other three emotional faces. These results indicate that low doses of alcohol affect positive emotional cognition of happy facial expressions.

Effects of concurrent use of alcohol and cocaine

The combination of alcohol and cocaine is popular among drug users, perhaps because of more intense feelings of 'high' beyond that perceived with either drug alone, less intense feelings of alcohol-induced inebriation and tempering of discomfort when coming down from a cocaine 'high'. A review is presented of the medical literature on psychological and somatic effects and consequences of combined use of alcohol and cocaine in man. The search was carried out with Medline, the Science Citation Index/Web of Science and Toxline. Exclusion and inclusion criteria for this search are identified. There is generally no evidence that the combination of the two drugs does more than enhance additively the already strong tendency of each drug to induce a variety of physical and psychological disorders. A few exceptions must be noted. Cocaine consistently antagonizes the learning deficits, psychomotor performance deficits and driving deficits induced by alcohol. The combination of alcohol and cocaine tends to have greater-than-additive effects on heart rate, concomitant with up to 30% increased blood cocaine levels. Both prospective and retrospective data further reveal that co-use leads to the formation of cocaethylene, which may potentiate the cardiotoxic effects of cocaine or alcohol alone. More importantly, retrospective data suggest that the combination can potentiate the tendency towards violent thoughts and threats, which may lead to an increase of violent behaviours.

Acute and chronic alcohol-cocaine interactions in rats

The widespread combined use of alcohol and cocaine across the United States underscores the importance of understanding how the actions of those two agents interact upon important physiological regulatory processes. In an experiment exploring acute ethanol-cocaine interactions, 16 rats were given 2.0 g/kg (IP) doses of ethanol at time zero. Two hours later, half of the rats were given cocaine (20 mg/kg, IP), while the other half were given injections of saline. The group given cocaine displayed a prolongation of the hypothermia condition induced by ethanol injection. In a chronic experiment, three groups of rats (n = 6-8) were exposed for an 11-day period to daily IP injections of 10 mg/kg cocaine, 20 mg/kg of cocaine, or saline. On day 12 these groups did not differ in their response to loss of the righting reflex induced by a 3.0 g/kg dose of ethanol. However, recovery from ethanol hypothermia was more rapid in the rats exposed to chronic cocaine. In summary, these initial studies provide evidence for exacerbation of the acute hypothermic effects of ethanol when a cocaine challenge is given 2 h after ethanol. In contrast, ethanol hypothermia was observed to be reduced when tested on day 12 after an 11-day chronic regimen of cocaine. Other dosage regimens and response measures need to be tested to understand the full scope of acute and chronic cocaine-ethanol interactions and the possible health consequences.

Alcohol plus cocaine: the whole is more than the sum of its parts

Cocaethylene, an active metabolite that arises through hepatic transesterification of cocaine when cocaine and ethanol are used together, shares many neurochemical and pharmacological properties with cocaine. Cocaethylene is similar to cocaine in its properties as an indirect dopamine agonist, and human subjects cannot distinguish its effects from those of cocaine. Cocaethylene, and especially its isopropyl analog, are more selective indirect dopamine agonists than cocaine, with relatively weak potency at the serotonin transporter. Cocaethylene may contribute to the manifestations and consequences of combined cocaine and ethanol use, although its relative importance remains unclear.