Pharmacology of Alcohol and Alcohol Use Disorder SpringerLink

In addition, CRF neurons projecting from the central amygdala to the BNST were shown to contribute to the escalation of alcohol intake. Prefrontal cortical circuits have been implicated in impaired executive control that underlies excessive drinking, as well as weakened cognitive function in AUD. For example, projections from the mPFC to the dorsal striatum have been linked to habitual alcohol drinking and continued use despite negative consequences. Further, neurons projecting from the mPFC to the dPAG play a critical role in compulsive drinking. Strikingly, mice that display inhibitory activity in this circuit during the first alcohol exposure are more likely to develop compulsive drinking behavior. We found that long-term alcohol consumption altered dorsal striatal dopamine release and uptake in a sex- and subregion-dependent manner.

• This reduction is consistent with the one prior study that tested the effects of P/T depletion on smoking AB [34].
• Both dopaminergic and nondopaminergic neurons also carry dopamine receptors that are located on the nerve terminals outside the synapse (i.e., are extrasynaptic).
• Since alcohol can increase the body’s production of dopamine and serotonin, two of the body’s ‘happy hormones’, it can temporarily make us feel less anxious.
• This 44 bp deletion occurs 1 kb upstream from the transcription initiation site of the gene.[53] This is depicted through the following diagram [Figure 4].

Our findings are the first to identify the dopamine-related functional connections underlying alcohol-related AB in humans. The results point to a significant role of dopamine for both alcohol and non-drug reward AB and indicate that specific dopamine-dependent functional connections between frontal, limbic, striatal, and brainstem regions mediate these behaviors. Here we quantified AB toward alcohol and non-drug, reward-conditioned cues and their neural underpinnings after acute dopamine precursor depletion across a broad spectrum of alcohol users.

The Connection Between Alcohol and Dopamine

Significant indirect effects indicate the functional connection significantly mediated the effect of beverage type on attentional bias. C is the direct effect without the mediator, and c′ is the effect after entering the mediator. In addition to the effect of ethanol on DA release, it can also affect the functioning of DA receptors, particularly D2 and D1 receptors. The D1 receptor binds with excitatory G protein and activates adenylate cyclase (AC) via Gs; AC catalyzes the production of cAMP and cAMP regulates cAMP-dependent protein kinases to open calcium ion channels.

Schematic representation of alcohol’s effects on the balance of inhibitory and excitatory neurotransmission in the brain. Recently mutations in the SERT gene, commonly known as 5’- hydroxtryptamine transporter linked polymorphic region (5’-HTTLPR), has been implicated in cases of alcoholism. One mutation is known as the “long” allele and the other mutation is known as the “short” allele. The difference between the two alleles is that the “short” version of the allele has a 44 bp deletion in the 5’ regulatory region of the gene. This 44 bp deletion occurs 1 kb upstream from the transcription initiation site of the gene.[53] This is depicted through the following diagram [Figure 4]. Dopamine is a neurotransmitter primarily involved in a circuit called the mesolimbic system, which projects from the brain’s ventral tegmental area to the nucleus accumbens.

National Institute on Alcohol Abuse and Alcoholism (NIAAA)

The Carolina Alcohol Use Patterns Questionnaire (CAUPQ [61]) was used to estimate a total number of adolescent (0–21 years) binge episodes (see Supplementary Materials) and quarter-root transformed before statistical analysis. Recently, a previously unanticipated mechanism was identified linking alcohol metabolism to alcohol-induced epigenetic impairments by way of direct incorporation of alcohol-derived acetate into brain histone acetylation [24]. This was driven by the nuclear translocation of metabolic enzyme acetyl-CoA synthetase 2 (Acss2), inhibition of which prevented alcohol-induced changes of histone acetylation and gene expression, and blocked conditioned place preference to alcohol [24]. This and related epigenetic-metabolic pathways [25] represent a radically novel mechanism of alcohol-induced transcriptional changes.

Finally, we can pharmacologically probe the contribution of different regulatory systems, including the D2 dopamine autoreceptor and nicotinic acetylcholine receptor (nAChR), to dopamine release. Neuroimaging studies have also dramatically advanced our understanding of the brain’s response to alcohol and the neurochemical basis of alcohol dependence. Positron emission tomography (PET) and single photon emission computed tomography (SPECT) use radiotracers that bind specifically to key receptors of interest, to quantify receptor location and availability. Neurotransmitter release can also be indirectly quantified using PET, through alcohol and dopamine measurement of the amount of tracer that is ‘displaced’ from the receptor when endogenous neurotransmitter is released in response to a pharmacological (or other) challenge. Such techniques have been instrumental in the investigation of key neurotransmitter systems and identification of molecular dysfunction in the human brain. The use of PET to study the effects of chronic alcohol consumption has advanced our understanding of reward mechanisms, neuroadaptations resulting from chronic use that led to tolerance and withdrawal and has identified key regions and circuits implicated in loss of control and motivation to drink.

Pain and reward circuits antagonistically modulate alcohol expectancy to regulate drinking

Thus, the connection between the trans-species conserved changes can be explored in the more tractable rodent models. In Drosophila, a mutant named intolerant was identified in a genetic screen for abnormal ethanol sensitivity and tolerance. The development of novel radiotracers with greater specificity for the dopamine D3 receptor allowed characterization of this subtype which has been shown in preclinical models to regulate alcohol consumption. Notably, no difference in binding in the ventral striatum or caudate or putamen was found, however, there was a significantly higher D3 receptor availability in the hypothalamus that was linked to higher lifetime use of alcohol [130]. Preclinical imaging has identified D3 receptor antagonism as a plausible therapeutic target to ameliorate alcoholism and its potential efficacy as an intervention is currently under investigation using fMRI [131] and combined PET/MR techniques [132].

“We have known for a long time that alcoholism runs in families, which implies a genetic risk,” said Dr. Raymond F. Anton, Distinguished Professor and director of the Center for Drug and Alcohol Programs at the Medical University of South Carolina. The developing adolescent brain is particularly vulnerable to alcohol-related harm. Alcohol is a powerful reinforcer in adolescents because the brain’s reward system is fully developed while the executive function system is not, and because there is a powerful social aspect to adolescent drinking. Specifically, prefrontal regions involved in executive functions and their connections to other brain regions are not fully developed in adolescents, which may make it harder for them to regulate the motivation to drink. Because the brain is adaptable and learns quickly during adolescence, and because alcohol is such a strong reinforcer for adolescents, alcohol use is more likely to be repeated, become a habit, and eventually evolve into a problematic drinking pattern that may lead to AUD.

Dopamine depletion effects on VTA FC

Underlying these maladaptive behaviors are short and long-term changes to neurotransmitters, receptors, synapses, and circuits. Understanding the neuromolecular targets of alcohol and how they are altered is critical to the development of novel AUD treatment strategies. There is evidence of gender- and sex-related differences in consumption of alcohol as well as its effects on the brain [153]. However, neuroimaging studies on the effects of alcohol use and dependence have either excluded women or shown low female enrolment [154]. Consideration of gender- and sex-related effects has also been limited, in part due to a lack of power [154]. Rates of alcohol dependence have increased drastically in women and many of the harmful health effects are more severe and occur more rapidly in women [155].

• For instance, while acute alcohol exposure increased histone acetylation and decreased histone methylation in the central amygdala (CeA), chronic intermittent exposure had opposite effects [20,21].
• However, relapse rates remain alarmingly high for those seeking total abstinence through traditional 12-step programs and rehab.
• Both reporters are positioned under the same promoter such that the relative relationship of the 2 signals conveys information about dynamic changes in gene expression.
• A phenomenon called long-term potentiation (LTP) appears to be fundamental for memory formation (Bliss and Collingridge 1993).
• The brain releases it when we eat food that we crave or while we have sex, contributing to feelings of pleasure and satisfaction as part of the reward system.
• To address these concerns and provide opportunities for improved patient outcomes there is a movement towards “harm reduction” by many addiction specialists.