Oxytocin Attenuates the Stress-Induced Reinstatement of Alcohol-Seeking in Male Rats: Role of the Central Amygdala

Oxytocin attenuates yohimbine-induced responding for oral oxycodone under a progressive ratio schedule in male and female rats

Opioid Use Disorder (OUD) has become an epidemic in the United States, with oxycodone (OXY) being one of the most widely misused opioids. Stress plays a key role in triggering opioid use, which can lead to addiction and relapse, underscoring the urgent need for effective therapeutic interventions. Recent studies suggest that the neuropeptide oxytocin (OXT) may reduce addiction-related behaviors and possess anxiolytic properties. The present study investigates the effect of peripheral administration of OXT on attenuating stress-induced motivation to seek oral OXY, as measured by progressive ratio (PR) responding in both male and female rats. Animals were first trained in an operant conditioning paradigm to orally self-administer a sucrose solution by pressing an active lever for access to the solution. As responding stabilized, subjects were switched to an OXY-sucrose solution, with sucrose concentration reduced overtime, until subjects were self-administering oral OXY alone. To test the effect of stress on OXY responding the pharmacological stressor, yohimbine (YOH), was administered prior to a progressive ratio test in which animals were required to produce increasingly higher responses to receive a single exposure to OXY. Through a within subjects design, when OXT was concurrently administered, this YOH-induced enhancement of OXY reward strength was attenuated in both male and female rats. These results suggest that OXT may serve as a potential therapeutic remedy to mitigate the deleterious effects of stress on OXY addiction in both sexes.

Oxytocin as a treatment for alcohol use disorder and heavy drinking: A narrative review

Oxytocin is increasingly being studied for treating symptoms of alcohol use disorders and heavy drinking behavior. The neuropeptide oxytocin facilitates social relationships and modulates the body's stress response by strengthening coping mechanisms and reducing anxiety. Relatedly, oxytocin is also thought to play a role in processes associated with craving and withdrawal from alcohol. This review aims to primarily provide an overview of preclinical and clinical literature on the applications of oxytocin in alcohol use, and additionally discuss a framework for types of trials and the variety of parameters that affect different study designs. A review of the existing literature in this area suggests that while low dosages of oxytocin do not affect drinking behavior and tolerance, higher dosages taken prior to alcohol exposure have varying behavioral and physiological results. Depending on quantity and timing, oxytocin treatments resulted in declines in withdrawal symptoms and alcohol self-administration in preclinical studies and may decrease neural cue reactivity and withdrawal symptoms in clinical studies. Current ongoing trials are expanding on this work to thoroughly explore clinical applications of oxytocin. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

Role of oxytocin and vasopressin in alcohol use disorder

Published works highlight the role of neuropeptides in both the development and treatment of AUD. Closely related hypothalamic neuropeptides, oxytocin (OT) and vasopressin (VP), initially recognized for their physiological hormone effects, are increasingly acknowledged for their behavioral influences. Studies consistently demonstrate that OT and VP impact alcohol consumption and related behaviors, implicating them in the neurobiology of addiction. Moreover, stress is a pivotal risk factor for alcohol use and relapse, with OT and VP playing an integral role in the body's stress response system. While previous work has explored the interaction of OT and VP with other substances of abuse, this review focuses on their roles in alcohol-associated behaviors specifically to better understand the role of OT and VP in AUD. Here we synthesize recent preclinical and clinical literature examining changes in OT and VP protein and receptor expression in response to alcohol, as well as research investigating the effects of modulating these systems on alcohol-related behaviors. This review aims to deepen the understanding of OT and VP in the context of AUD with the goal of facilitating future research and enhancing treatment outcomes.

Oxytocin attenuates cocaine-associated place preference via the dorsal hippocampus in male and female rats

Cocaine addiction is the third largest cause of overdose-related deaths in the United States. Research investigating therapeutic targets for cocaine reward processes is key to combating this issue. The neuropeptide oxytocin (OXT) has been shown to reduce cocaine reward processes, though specific mechanisms are not understood. This study examines the effect of intra-dorsal hippocampal (DH) OXT on the expression of cocaine context associations using a conditioned place preference (CPP) paradigm. In this paradigm, one of two visually distinct chambers is paired with a drug. With repeated pairings, control animals display preference for the drug-associated context by spending more time in that context at test. In the present study, four conditioning days took place where male and female rats were injected with either cocaine or saline and placed into the corresponding chamber. On test day, rats received infusions of OXT or saline (VEH) into the DH and were allowed access to both chambers. The results show that while VEH-infused rats displayed cocaine CPP, OXT-infused rats did not prefer the cocaine-paired chamber. These findings implicate the DH as necessary in the mechanism by which OXT acts to block the expression of cocaine-context associations, providing insight into how OXT may exert its therapeutic effect in cocaine reward processes.

Effects of systemic oxytocin receptor activation and blockade on risky decision making in female and male rats

The neuropeptide oxytocin is traditionally known for its roles in parturition, lactation, and social behavior. Other data, however, show that oxytocin can modulate behaviors outside of these contexts, including drug self-administration and some aspects of cost-benefit decision making. Here we used a pharmacological approach to investigate the contributions of oxytocin signaling to decision making under risk of explicit punishment. Female and male Long-Evans rats were trained on a risky decision-making task in which they chose between a small, "safe" food reward and a large, "risky" food reward that was accompanied by varying probabilities of mild footshock. Once stable choice behavior emerged, rats were tested in the task following acute intraperitoneal injections of oxytocin or the oxytocin receptor antagonist L-368,899. Neither drug affected task performance in males. In females, however, both oxytocin and L-368,899 caused a dose-dependent reduction in preference for large risky reward. Control experiments showed that these effects could not be accounted for by alterations in food motivation or shock sensitivity. Together, these results reveal a sex-dependent effect of oxytocin signaling on risky decision making in rats.

Oxytocin Reduces Sensitized Stress-Induced Alcohol Relapse in a Model of Posttraumatic Stress Disorder and Alcohol Use Disorder Comorbidity

BACKGROUND

There is high comorbidity of posttraumatic stress disorder (PTSD) and alcohol use disorder with few effective treatment options. Animal models of PTSD have shown increases in alcohol drinking, but effects of stress history on subsequent vulnerability to alcohol relapse have not been examined. Here we present a mouse model of PTSD involving chronic multimodal stress exposure that resulted in long-lasting sensitization to stress-induced alcohol relapse, and this sensitized stress response was blocked by oxytocin (OT) administration.

METHODS

Male and female mice trained to self-administer alcohol were exposed to predator odor (TMT) + yohimbine over 5 consecutive days or left undisturbed. After reestablishing stable alcohol responding/intake, mice were tested under extinction conditions, and then all mice were exposed to TMT or context cues previously associated with TMT before a reinstatement test session. Separate studies examined messenger RNA expression of Oxt and Oxtr in hypothalamus following chronic stress exposure. A final study examined the effects of systemic administration of OT on stress-induced alcohol relapse in mice with and without a history of chronic stress experience.

RESULTS

Chronic stress exposure produced long-lasting sensitization to subsequent stress-induced alcohol relapse that also generalized to stress-related context cues and transcriptional changes in hypothalamic OT system. OT injected before the reinstatement test session completely blocked the sensitized stress-induced alcohol relapse effect.

CONCLUSIONS

Collectively, these results provide support for the therapeutic potential of OT, along with highlighting the value of utilizing this model in evaluating other pharmacological interventions for treatment of PTSD/alcohol use disorder comorbidity.

Oxytocin Attenuates Yohimbine-Induced Reinstatement of Alcohol-Seeking in Female Rats via the Central Amygdala

Alcohol use disorder is a significant public health concern, further exacerbated by an increased risk of relapse due to stress. In addition, factors such as biological sex may contribute to the progression of addiction, as females are especially susceptible to stress-induced relapse. While there have been many studies surrounding potential pharmacological interventions for male stress-induced ethanol reinstatement, research regarding females is scarce. Recently, the neuropeptide oxytocin has gained interest as a possible pharmacological intervention for relapse. The present study examines how oxytocin affects yohimbine-induced reinstatement of ethanol-seeking in female rats using a self-administration paradigm. Adult female rats were trained to press a lever to access ethanol in daily self-administration sessions. Rats then underwent extinction training before a yohimbine-induced reinstatement test. Rats administered with yohimbine demonstrated significantly higher lever response indicating a reinstatement of ethanol-seeking behavior. Oxytocin administration, both systemically and directly into the central amygdala, attenuated the effect of yohimbine-induced reinstatement of ethanol-seeking behavior. The findings from this study establish that oxytocin is effective at attenuating alcohol-relapse behavior mediated by the pharmacological stressor yohimbine and that this effect is modulated by the central amygdala in females. This provides valuable insight regarding oxytocin's potential therapeutic effect in female stress-induced alcohol relapse.

The maladaptive alcohol self-administration task: An adapted novel model of alcohol seeking with negative consequences

The progression of recreational drinking to alcohol use disorder is characterized by loss of control over seeking, which involves continued use of alcohol despite negative consequences. The present study proposes a novel maladaptive alcohol self-administration task in which animals are trained to withhold alcohol drinking in the presence of an auditory cue signaling consequence (conflict phase) but to drink freely when there is no consequence (neutral phase). These phases are performed within trial; successful performance involves waiting for the conflict phase to end and drinking during the neutral phase. We discuss the background and implementation of the task, its relation to existing models, and its relevance to the field of translational alcohol research. Importantly, we also present evidence of its efficacy. Both male and female Long-Evans rats are capable of performing the maladaptive alcohol self-administration task for both sweetened and unsweetened alcohol solutions. Finally, we show that acute injection of a pharmacological stressor (yohimbine) significantly disrupted performance of the task in both sexes and reinforcers. We suggest the maladaptive alcohol self-administration task may prove particularly useful in models of alcohol use disorder or vulnerability to this disorder where its application may reveal maladaptive neural circuit adaptations responsible for motivational perturbations associated with loss of control over alcohol seeking.

Paired Housing or a Socially-Paired Context Decreases Ethanol Conditioned Place Preference in Male Rats

Alcohol abuse dramatically affects individuals’ lives nationwide. The 2020 National Survey on Drug Use and Health (NSDUH) estimated that 10.2% of Americans suffer from alcohol use disorder. Although social support has been shown to aid in general addiction prevention and rehabilitation, the benefits of social support are not entirely understood. The present study sought to compare the benefits of social interaction on the conditioned ethanol approach behavior in rats through a conditioned place preference (CPP) paradigm in which a drug is paired with one of two distinct contexts. In experiment 1A, rats were single-housed and received conditioning trials in which ethanol was paired with the less preferred context. In experiment 1B, rats underwent procedures identical to experiment 1A, but were pair-housed throughout the paradigm. In experiment 1C, rats were single-housed, but concurrently conditioned to a socially-paired context and an ethanol-paired context. By comparing the time spent between the ethanol-paired environment and the saline-paired or socially-paired environment, we extrapolated the extent of ethanol approach behavior in the pair-housed, single-housed, and concurrently conditioned rats. Our results revealed that social interaction, both in pair-housed animals or concurrently socially-conditioned animals, diminished the ethanol approach behavior, which highlights the importance of social support in addiction prevention, treatment, and recovery programs.

Oxytocin and orexin systems bidirectionally regulate the ability of opioid cues to bias reward seeking

As opioid-related fatalities continue to rise, the need for novel opioid use disorder (OUD) treatments could not be more urgent. Two separate hypothalamic neuropeptide systems have shown promise in preclinical OUD models. The oxytocin system, originating in the paraventricular nucleus (PVN), may protect against OUD severity. By contrast, the orexin system, originating in the lateral hypothalamus (LH), may exacerbate OUD severity. Thus, activating the oxytocin system or inhibiting the orexin system are potential therapeutic strategies. The specific role of these systems with regard to specific OUD outcomes, however, is not fully understood. Here, we probed the therapeutic efficacy of pharmacological interventions targeting the orexin or oxytocin system on two distinct metrics of OUD severity in rats-heroin choice (versus choice for natural reward, i.e., food) and cued reward seeking. Using a preclinical model that generates approximately equal choice between heroin and food reward, we examined the impact of exogenously administered oxytocin, an oxytocin receptor antagonist (L-368,899), and a dual orexin receptor antagonist (DORA-12) on opioid choice. Whereas these agents did not alter heroin choice when rewards (heroin and food) were available, oxytocin and DORA-12 each significantly reduced heroin seeking in the presence of competing reward cues when no rewards were available. In addition, the number of LH orexin neurons and PVN oxytocin neurons correlated with specific behavioral economic variables indicative of heroin versus food motivation. These data identify a novel bidirectional role of the oxytocin and orexin systems in the ability of opioid-related cues to bias reward seeking.

Melanin-concentrating hormone promotes anxiety and intestinal dysfunction via basolateral amygdala in mice

The limbic system plays a pivotal role in stress-induced anxiety and intestinal disorders, but how the functional circuits between nuclei within the limbic system are engaged in the processing is still unclear. In our study, the results of fluorescence gold retrograde tracing and fluorescence immunohistochemistry showed that the melanin-concentrating hormone (MCH) neurons of the lateral hypothalamic area (LHA) projected to the basolateral amygdala (BLA). Both chemogenetic activation of MCH neurons and microinjection of MCH into the BLA induced anxiety disorder in mice, which were reversed by intra-BLA microinjection of MCH receptor 1 (MCHR1) blocker SNAP-94847. In the chronic acute combining stress (CACS) stimulated mice, SNAP94847 administrated in the BLA ameliorated anxiety-like behaviors and improved intestinal dysfunction via reducing intestinal permeability and inflammation. In conclusion, MCHergic circuit from the LHA to the BLA participates in the regulation of anxiety-like behavior in mice, and this neural pathway is related to the intestinal dysfunction in CACS mice by regulating intestinal permeability and inflammation.

Oxytocin moderates corticolimbic social stress reactivity in cocaine use disorder and healthy controls

Social stress can contribute to the development of substance use disorders (SUDs) and increase the likelihood of relapse. Oxytocin (OT) is a potential pharmacotherapy that may buffer the effects of social stress on arousal and reward neurocircuitry. However, more research is needed to understand how OT moderates the brain’s response to social stress in SUDs. The present study examined the effect of intransasal OT (24 IU) versus placebo (PBO) on corticolimbic functional connectivity associated with acute social stress in individuals with cocaine use disorder (CUD; n = 67) and healthy controls (HC; n = 52). Psychophysiological interaction modeling used the left and right amygdala as seed regions with the left and right orbitofrontal and anterior cingulate cortex as a priori regions of interest. Moderators of the OT response included childhood trauma history and biological sex, which were examined in independent analyses. The main finding was that OT normalized corticolimbic connectivity (left amygdala-orbitofrontal and left amygdala-anterior cingulate) as a function of childhood trauma such that connectivity was different between trauma-present and trauma-absent groups on PBO, but not between trauma groups on OT. Effects of OT on corticolimbic connectivity were not different as a function of diagnosis (CUD vs HC) or sex. However, OT reduced subjective anxiety during social stress for CUD participants who reported childhood trauma compared to PBO and normalized craving response as a function of sex in CUD. The present findings add to some prior findings of normalizing effects of OT on corticolimbic circuitry in individuals with trauma histories and provide some initial support that OT can normalize subjective anxiety and craving in CUD.

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Social stress-related corticolimbic connectivity was affected by childhood trauma under placebo.

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Under oxytocin, corticolimbic connectivity differences due to childhood trauma were absent.

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Oxytocin reduced subjective anxiety in cocaine users with childhood trauma.

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Oxytocin reduced subjective craving in male cocaine users.

Sex differences in stress-induced alcohol intake: a review of preclinical studies focused on amygdala and inflammatory pathways

Clinical studies suggest that women are more likely than men to relapse to alcohol drinking in response to stress; however, the mechanisms underlying this sex difference are not well understood. A number of preclinical behavioral models have been used to study stress-induced alcohol intake. Here, we review paradigms used to study effects of stress on alcohol intake in rodents, focusing on findings relevant to sex differences. To date, studies of sex differences in stress-induced alcohol drinking have been somewhat limited; however, there is evidence that amygdala-centered circuits contribute to effects of stress on alcohol seeking. In addition, we present an overview of inflammatory pathways leading to microglial activation that may contribute to alcohol-dependent behaviors. We propose that sex differences in neuronal function and inflammatory signaling in circuits centered on the amygdala are involved in sex-dependent effects on stress-induced alcohol seeking and suggest that this is an important area for future studies.