Treatment of cocaine withdrawal anxiety with guanfacine: relationships to cocaine intake and reinstatement of cocaine seeking in rats

Tranq Dope: Characterization of an ED cohort treated with a novel opioid withdrawal protocol in the era of fentanyl/xylazine

BACKGROUND

Treating opioid use disorder has reached a new level of challenge. Synthetic opioids and xylazine have joined the non-medical opioid supply, multiplying the complexities of caring for individuals in emergency departments (ED). This combination, known as 'tranq dope,' is poorly described in literature. Inadequate withdrawal treatment results in a disproportionately high rate of patient-directed discharges (also known as against medical advice dispositions, or AMA). This study aimed to describe a cohort of individuals who received a novel order set for suspected fentanyl and xylazine withdrawal in the ED.

METHODS

This is a descriptive study evaluating a cohort of ED patients who received withdrawal medications from a novel protocol and electronic health record order set. Individuals being assessed in the ED while suffering from withdrawal were eligible. Individuals under age 18, on stable outpatient MOUD or who were pregnant were excluded. Treatment strategies included micro-induction buprenorphine, short acting opioids, non-opioid analgesics, and other adjunctive medications. Data collected included: demographics including zip code, urine toxicology screening, order set utilization and disposition data. Clinical Opiate Withdrawal Scale (COWS) scores were recorded, where available, before and following exposure to the medications.

RESULTS

There were 270 patient encounters that occurred between September 14, 2022, and March 9, 2023 included in the total study cohort. Of those, 66 % were male, mean age 37 with 71 % residing within Philadelphia zip codes. 100 % of urine toxicology screenings were positive for fentanyl. Of the 177 patients with both pre- and post-exposure COWS scores documented, constituting the final cohort, patients receiving medications had their COWS score decrease from a median of 12 to a median of 4 (p < 0.001). The AMA rate for this cohort was 3.9 %, whereas the baseline for the population with OUD was 10.7 %. Recorded adverse effects were few and resolved without complication.

CONCLUSIONS

Fentanyl and xylazine withdrawal are challenging for patients and providers. A novel tranq dope withdrawal order set may reduce both COWS scores and rate of patient-directed discharge in this cohort of patients, though further investigation is needed to confirm findings.

Pharmacological Treatments for Methamphetamine Use Disorder: Current Status and Future Targets

The illicit use of the psychostimulant methamphetamine (METH) is a major concern, with overdose deaths increasing substantially since the mid-2010s. One challenge to treating METH use disorder (MUD), as with other psychostimulant use disorders, is that there are no available pharmacotherapies that can reduce cravings and help individuals achieve abstinence. The purpose of the current review is to discuss the molecular targets that have been tested in assays measuring the physiological, the cognitive, and the reinforcing effects of METH in both animals and humans. Several drugs show promise as potential pharmacotherapies for MUD when tested in animals, but fail to produce long-term changes in METH use in dependent individuals (eg, modafinil, antipsychotic medications, baclofen). However, these drugs, plus medications like atomoxetine and varenicline, may be better served as treatments to ameliorate the psychotomimetic effects of METH or to reverse METH-induced cognitive deficits. Preclinical studies show that vesicular monoamine transporter 2 inhibitors, metabotropic glutamate receptor ligands, and trace amine-associated receptor agonists are efficacious in attenuating the reinforcing effects of METH; however, clinical studies are needed to determine if these drugs effectively treat MUD. In addition to screening these compounds in individuals with MUD, potential future directions include increased emphasis on sex differences in preclinical studies and utilization of pharmacogenetic approaches to determine if genetic variances are predictive of treatment outcomes. These future directions can help lead to better interventions for treating MUD.

Critical appraisal and systematic review of genes linked with cocaine addiction, depression and anxiety

Recent lifestyle changes have resulted in tremendous peer pressure and mental stress, and increased the incidences of chronic psychological disorders; like addiction, depression and anxiety (ADA). In this context, the stress-tolerance levels vary amongst individuals and genetic factors play prominent roles. Vulnerable individuals may often be drawn towards drug-addiction to combat stress. This systematic review critically appraises the relationship of various genetic factors linked with the incidences of ADA development. For coherence, we focused solely on cocaine as a substance of abuse in this study. Online scholarly databases were used to screen pertinent literature using apt keywords; and the final retrieval included 42 primary-research articles. The major conclusion drawn from this systematic analysis states that there are 51 genes linked with the development of ADA; and 3 (BDNF, PERIOD2 and SLC6A4) of them are common to all the three aspects of ADA. Further, inter-connectivity analyses of the 51 genes further endorsed the central presence of BDNF and SLC6A4 genes in the development of ADA disorders. The conclusions derived from this systematic study pave the way for future studies for the identification of diagnostic biomarkers and drug targets; and for the development of novel and effective therapeutic regimens against ADA.

An ensemble recruited by α2a-adrenergic receptors is engaged in a stressor-specific manner in mice

α2a-adrenergic receptor (α2a-AR) agonists are candidate substance use disorder therapeutics due to their ability to recruit noradrenergic autoreceptors to dampen stress system engagement. However, we recently found that postsynaptic α2a-ARs are required for stress-induced reinstatement of cocaine-conditioned behavior. Understanding the ensembles recruited by these postsynaptic receptors (heteroceptors) is necessary to understand noradrenergic circuit control. We utilized a variety of approaches in FosTRAP (Targeted Recombination in Active Populations) mice to define an ensemble of cells activated by the α2a-AR partial agonist guanfacine ("Guansembles") in the bed nucleus of the stria terminalis (BST/BNST), a region key to stress-induced reinstatement of drug seeking. We define BNST "Guansembles" and show they differ from restraint stress-activated cells. Guanfacine produced inhibition of cAMP-dependent signaling in Guansembles, while chronic restraint stress increased cAMP-dependent signaling. Guanfacine both excited and inhibited aspects of Guansemble neuronal activity. Further, while some stressors produced overall reductions in Guansemble activity, active coping events during restraint stress and exposure to unexpected shocks were both associated with Guansemble recruitment. Using viral tracing, we define a BNST Guansemble afferent network that includes regions involved in the interplay of stress and homeostatic functions. Finally, we show that activation of Guansembles produces alterations in behavior on the elevated plus maze consistent with task-specific anxiety-like behavior. Overall, we define a population of BNST neurons recruited by α2a-AR signaling that opposes the behavioral action of canonical autoreceptor α2a-AR populations and which are differentially recruited by distinct stressors. Moreover, we demonstrate stressor-specific physiological responses in a specific neuronal population.

Therapeutics for Substance-Using Women: The Need to Elucidate Sex-Specific Targets for Better-Tailored Treatments

In the last decade, alcohol consumption in the US has risen by 84% in women compared with 35% in men. Furthermore, research has shown that sex- and gender-related differences may disadvantage women in terms of developing a range of psychological, cognitive, and medical problems considerably earlier in their drinking history than men, and despite consuming a similar quantity of substances. While this "telescoping" process has been acknowledged in the literature, a concomitant understanding of the underlying biobehavioral mechanisms, and an increase in the development of specific treatments tailored to women, has not occurred. In the current chapter we focus on understanding why the need for personalized, sex-specific medications is imperative, and highlight some of the potential sex-specific gonadal and stress-related adaptations underpinning the accelerated progress from controlled to compulsive drug and alcohol seeking in women. We additionally discuss the efficacy of these mechanisms as novel targets for medications development, using exogenous progesterone and guanfacine as examples. Finally, we assess some of the challenges faced and progress made in terms of developing innovative medications in women. We suggest that agents such as exogenous progesterone and adrenergic medications, such as guanfacine, may provide some efficacy in terms of attenuating stress-induced craving for several substances, as well as improving the ability to emotionally regulate in the face of stress, preferentially in women. However, to fully leverage the potential of these therapeutics in substance-using women, greater focus needs to the placed on reducing barriers to treatment and research by encouraging women into clinical trials.

Brain systems in cocaine abstinence-induced anxiety-like behavior in rodents: A review

Cocaine use disorder (CUD) is a significant public health issue that generates substantial personal, familial, and economic burdens. Still, there are no FDA-approved pharmacotherapies for CUD. Cocaine-dependent individuals report anxiety during withdrawal, and alleviation of anxiety and other negative affective states may be critical for maintaining drug abstinence. However, the neurobiological mechanisms underlying abstinence-related anxiety in humans or anxiety-like behavior in rodents are not fully understood. This review summarizes investigations regarding anxiety-like behavior in mice and rats undergoing cocaine abstinence, as assessed using four of the most common anxiety-related assays: the elevated plus (or its derivative, the elevated zero) maze, open field test, light-dark transition test, and defensive burying task. We first summarize available evidence that cocaine abstinence generates anxiety-like behavior that persists throughout protracted abstinence. Then, we examine investigations concerning neuropeptide, neurotransmitter, and neuromodulator systems in cocaine abstinence-induced anxiety-like behavior. Throughout, we discuss how differences in sex, rodent strain, cocaine dose and dosing strategy and abstinence duration interact to generate anxiety-like behavior.

Dissociation Between Incubation of Cocaine Craving and Anxiety-Related Behaviors After Continuous and Intermittent Access Self-Administration

Studies using either continuous or intermittent access cocaine self-administration procedures showed that cocaine seeking increases during abstinence (incubation of cocaine craving), and that this effect is higher after intermittent cocaine access. Other studies showed that cocaine abstinence is characterized by the emergence of stress- and anxiety-related states which were hypothesized to increase relapse vulnerability. We examined whether incubation of cocaine craving and anxiety-related behaviors are correlated and whether intermittent cocaine self-administration would potentiate these behaviors during abstinence. Male rats self-administered cocaine either continuously (6 h/day) or intermittently (5 min ON, 25 min OFF × 12) for 14 days, followed by relapse tests after 1 or 21 abstinence days. A group of rats that self-administered saline served as a control. Anxiety-related behaviors were measured on the same abstinence days, using the novelty induced-hypophagia test. Finally, motivation for cocaine was measured using a progressive ratio reinforcement schedule. Lever-presses after 21 abstinence days were higher than after 1 day and this incubation effect was higher in the intermittent access group. Progressive ratio responding was also higher after intermittent cocaine access. Intermittent and continuous cocaine access did not induce anxiety-like responses in the novelty-induced hypophagia test after 1 or 21 abstinence days. Independent of the access condition, incubation of cocaine seeking was not correlated with the novelty-induced hypophagia measures. Results suggest that cocaine-induced anxiety-related states during protracted abstinence do not contribute to incubation of cocaine craving. However, this conclusion is tentative because we used a single anxiety-related measure and did not test female rats.

Consideration of sex as a biological variable in the translation of pharmacotherapy for stress-associated drug seeking

Stress is a frequent precipitant of relapse to drug use. Pharmacotherapies targeting a diverse array of neural systems have been assayed for efficacy in attenuating stress-induced drug-seeking in both rodents and in humans, but none have shown enough evidence of utility to warrant routine use in the clinic. We posit that a critical barrier in effective translation is inattention to sex as a biological variable at all phases of the research process. In this review, we detail the neurobiological systems implicated in stress-induced relapse to cocaine, opioids, methamphetamine, and cannabis, as well as the pharmacotherapies that have been used to target these systems in rodent models, the human laboratory, and in clinical trials. In each of these areas we additionally describe the potential influences of biological sex on outcomes, and how inattention to fundamental sex differences can lead to biases during drug development that contribute to the limited success of large clinical trials. Based on these observations, we determine that of the pharmacotherapies discussed only α₂-adrenergic receptor agonists and oxytocin have a body of research with sufficient consideration of biological sex to warrant further clinical evaluation. Pharmacotherapies that target β-adrenergic receptors, other neuroactive peptides, the hypothalamic-pituitary-adrenal axis, neuroactive steroids, and the endogenous opioid and cannabinoid systems require further assessment in females at the preclinical and human laboratory levels before progression to clinical trials can be recommended.

The effects of cocaine exposure in adolescence: Behavioural effects and neuroplastic mechanisms in experimental models

Drug addiction is a devastating disorder with a huge economic and social burden for modern society. Although an individual may slip into drug abuse throughout his/her life, adolescents are at higher risk, but, so far, only a few studies have attempted to elucidate the underlying cellular and molecular bases of such vulnerability. Indeed, preclinical evidence indicates that psychostimulants and adolescence interact and contribute to promoting a dysfunctional brain. In this review, we have focused our attention primarily on changes in neuroplasticity brought about by cocaine, taking into account that there is much less evidence from exposure to cocaine in adolescence, compared with that from adults. This review clearly shows that exposure to cocaine during adolescence, acute or chronic, as well as contingent or non‐contingent, confers a vulnerable endophenotype, primarily, by causing changes in neuroplasticity. Given the close relationship between drug abuse and psychiatric disorders, we also discuss the translational implications providing an interpretative framework for clinical studies involving addictive as well as affective or psychotic behaviours.

Corticotropin Releasing Hormone Signaling in the Bed Nuclei of the Stria Terminalis as a Link to Maladaptive Behaviors

The bed nuclei of the stria terminalis (BST) is a limbic region in the extended amygdala that is heavily implicated in anxiety processing and hypothalamic-adrenal-pituitary (HPA) axis activation. The BST is complex, with many nuclei expressing different neurotransmitters and receptors involved in a variety of signaling pathways. One neurotransmitter that helps link its functions is corticotropin releasing hormone (CRH). BST CRH neuron activation may cause both anxiogenic and anxiolytic effects in rodents, and CRH neurons interact with other neuron types to influence anxiety-like responses as well as alcohol and drug–seeking behavior. This review covers the link between BST CRH neurons and thirteen other neurotransmitters and receptors and analyzes their effect on rodent behavior. Additionally, it covers the translational potential of targeting CRH signaling pathways for the treatment of human mental health disorders. Given the massive impact of anxiety, mood, and substance use disorders on our society, further research into BST CRH signaling is critical to alleviate the social and economic burdens of those disorders.

Extinction and drug-induced reinstatement of cocaine seeking following self-administration or conditioned place preference in adolescent and adult rats

Adolescence marks a particularly vulnerable period to developing substance use disorders, and people who start using drugs in adolescence are more likely to relapse. A limited number of studies have investigated age difference in relapse following re-exposure to the drug after a period of abstinence. Using a cocaine self-administration paradigm, we showed no age difference in acquisition or extinction of self-administration. Interestingly, adolescent rats displayed impaired cocaine-primed reinstatement of cocaine seeking. Using the same dose as that self-administered in the first experiment, we then investigated age differences in acquisition and extinction of conditioned place preference, as well as locomotor sensitization. While there were no differences in locomotor activity or acquisition of preference, adolescents failed to extinguish their preference, even when the number of extinction sessions was doubled from what adults received. Taken together, these results suggest that while cocaine has similar rewarding and reinforcing effects regardless of age, adolescents may attribute stronger salience to the drug-associated context. In addition, re-exposure to cocaine itself may not be a strong relapse trigger in adolescence. Overall, these findings suggest that we should focus more on alleviating drug-context salience compared to re-exposure to substance in order to reduce relapse of drug seeking in adolescents.

Effects of the α-2 Adrenergic Receptor Agonists Lofexidine and Guanfacine on Food-Cocaine Choice in Socially Housed Cynomolgus Monkeys

Although norepinephrine (NE) does not appear to play a prominent role in mediating the abuse-related effects of cocaine, studies have indicated that NE α-2 receptor agonists can attenuate reinstatement of extinguished cocaine self-administration in rats and monkeys and can decrease cocaine craving in humans. In the present studies, we examined the effects of two α-2 receptor agonists, lofexidine and guanfacine, on choice between food and cocaine (0.0-0.1 mg/kg per injection) in cynomolgus monkeys. Male and female subjects were housed in stable same-sex social groups of four; social rank did not influence the effects of lofexidine and guanfacine. When administered acutely, lofexidine (0.03-3.0 mg/kg, i.v.) significantly decreased cocaine choice in females (n = 7) but not males (n = 8). However, in males, the same lofexidine doses produced dose-dependent decreases in core body temperature (n = 7), and acute guanfacine (0.003-1.0 mg/kg, i.v.) significantly decreased cocaine choice (n = 11). When lofexidine was administered for five consecutive days to a subset of the monkeys in whom lofexidine acutely decreased cocaine choice, tolerance to this effect developed to varying degrees of completeness in three of three males and two of four females. Taken together, these data suggest that α-2 receptor agonists can produce small decreases in the reinforcing strength of cocaine relative to food and that, even when efficacy is observed after acute administration, tolerance to the decreases in cocaine choice are apparent and more likely in males compared with females. SIGNIFICANCE STATEMENT: Cocaine use disorder remains a significant public health problem with no US Food and Drug Administration-approved treatments. Although cocaine elevates dopamine, serotonin, and norepinephrine (NE), the latter target has received less research. The present study noted modest effects of NE agonists on the relative reinforcing strength of cocaine with greater efficacy in female compared with male monkeys.

Sex differences in the effect of the FKBP5 inhibitor SAFit2 on anxiety and stress-induced reinstatement following cocaine self-administration

Cocaine use and withdrawal prompt stress system responses. Stress and the negative affective state produced by cocaine withdrawal are major triggers for relapse. FKBP5 is a co-chaperone of the glucocorticoid receptor and regulates HPA axis negative feedback. The role of FKBP5 in cocaine-related behaviors has not been studied. The FKBP5 inhibitor SAFit2 was used to examine the role of FKBP5 in anxiety-like behavior during early cocaine withdrawal and in stress-induced reinstatement following cocaine self-administration in male and female rats. Withdrawal from cocaine self-administration resulted in heightened anxiety-like behavior in female rats, which was significantly attenuated by SAFit2 administration. SAFit2 pretreatment prior to stress-induced reinstatement to cocaine seeking significantly reduced active lever presses of males. In female rats, SAFit2 administration prevented stress-induced reinstatement for rats in metestrus or diestrus, but not proestrus or estrus phases at the time of reinstatement. These data suggest an important role for FKBP5 in stress-related behaviors following cocaine self-administration, particularly in females.

MicroRNA134 of Ventral Hippocampus Is Involved in Cocaine Extinction-Induced Anxiety-like and Depression-like Behaviors in Mice

We previously found that cocaine abuse could increase microRNA134 (miR134) levels in the hippocampus; yet the roles of miR134 in cocaine-related abnormal psychiatric outcomes remain unknown. In this study, using the cocaine-induced conditioned place preference (CPP) mice model, we found that mice exhibit enhanced anxiety-like and depression-like behaviors during the cocaine extinction (CE) period of CPP, accompanied by obviously increased miR134 levels and decreased levels of 19 genes that are associated with synaptic plasticity, glia activity, and neurochemical microenvironments, in the ventral hippocampus (vHP). Knockdown of miR134 in vHP in vivo reversed the changes in 15 of 19 potential gene targets of miR134 and rescued the abnormal anxiety-like and depression-like behavioral outcomes in CE mice. In parallel, knockdown of miR134 reversed CE-induced changes in dendritic spines and synaptic proteins and increased the field excitatory postsynaptic potential (fEPSP) of CA1 pyramidal neurons in the vHP of CE mice. In addition, knockdown of miR134 suppressed the CE-enhanced microglia activity, inflammatory, apoptotic, and oxidative stress statuses in the vHP. With the data taken together, miR134 may be involved in cocaine-associated psychiatric problems, potentially via regulating the expressions of its gene targets that are related to synaptic plasticity and neurochemical microenvironments.

Effects of cocaine base paste on anxiety-like behavior and immediate-early gene expression in nucleus accumbens and medial prefrontal cortex of female mice

RATIONALE

Cocaine base paste (CBP) is an illegal drug of abuse usually consumed by adolescents in a socio-economically vulnerable situation. Repeated drug use targets key brain circuits disrupting the processes that underlie emotions and cognition. At the basis of such neuroadaptations lie changes in the expression of immediate-early genes (IEGs). Nevertheless, changes in transcriptional regulation associated with CBP consumption remain unknown.

OBJECTIVES

We aimed to describe behavioral phenotype related to locomotion, anxiety-like behavior, and memory of CBP-injected mice and to study IEGs expression after an abstinence period.

METHODS

Five-week-old female CF-1 mice were i.p. injected daily with vehicle or CBP (40 mg/kg) for 10 days and subjected to a 10-day period of abstinence. Open field and novel object recognition tests were used to evaluate locomotion and anxiety-like behaviors and recognition memory, respectively, during chronic administration and after abstinence. After abstinence, prefrontal cortex (mPFC) and nucleus accumbens (NAc) were isolated and gene expression analysis performed through real-time PCR.

RESULTS

We found an increase in locomotion and anxiety-like behavior during CBP administration and after the abstinence period. Furthermore, the CBP group showed impaired recognition memory after abstinence. Egr1, FosB, ΔFosB, Arc, Bdnf, and TrkB expression was upregulated in CBP-injected mice in NAc and FosB, ΔFosB, Arc, and Npas4 expression was downregulated in mPFC. We generated an anxiety score and found positive and negative correlations with IEGs expression in NAc and mPFC, respectively.

CONCLUSION

Our results suggest that chronic CBP exposure induced alterations in anxiety-like behavior and recognition memory. These changes were accompanied by altered IEGs expression.

Cholinergic Receptor Blockade in the VTA Attenuates Cue-Induced Cocaine-Seeking and Reverses the Anxiogenic Effects of Forced Abstinence

Drug relapse after periods of abstinence is a common feature of substance abuse. Moreover, anxiety and other mood disorders are often co-morbid with substance abuse. Cholinergic receptors in the ventral tegmental area (VTA) are known to mediate drug-seeking and anxiety-related behavior in rodent models. However, it is unclear if overlapping VTA cholinergic mechanisms mediate drug relapse and anxiety-related behaviors associated with drug abstinence. We examined the effects of VTA cholinergic receptor blockade on cue-induced cocaine seeking and anxiety during cocaine abstinence. Male Sprague-Dawley rats were trained to self-administer intravenous cocaine (~0.5 mg/kg/infusion, FR1 schedule) for 10 days, followed by 14 days of forced abstinence. VTA infusion of the non-selective nicotinic acetylcholine receptor antagonist mecamylamine (0, 10, and 30 μg/side) or the non-selective muscarinic receptor antagonist scopolamine (0, 2.4 and 24 μg /side) significantly decreased cue-induced cocaine seeking. In cocaine naïve rats, VTA mecamylamine or scopolamine also led to dose-dependent increases in open arm time in the elevated plus maze (EPM). In contrast, rats that received I.V. cocaine, compared to received I.V. saline rats, displayed an anxiogenic response on day 14 of abstinence as reflected by decreased open arm time in the EPM. Furthermore, low doses of VTA mecamylamine (10 μg /side) or scopolamine (2.4 μg /side), that did not alter EPM behavior in cocaine naive rats, were sufficient to reverse the anxiogenic effects of cocaine abstinence. Together, these data point to an overlapping role of VTA cholinergic mechanisms to regulate relapse and mood disorder-related responses during cocaine abstinence.

The intersection of stress and reward: BNST modulation of aversive and appetitive states

The bed nucleus of the stria terminalis (BNST) is widely acknowledged as a brain structure that regulates stress and anxiety states, as well as aversive and appetitive behaviours. The diverse roles of the BNST are afforded by its highly modular organisation, neurochemical heterogeneity, and complex intrinsic and extrinsic circuitry. There has been growing interest in the BNST in relation to psychopathologies such as anxiety and addiction. Although research on the human BNST is still in its infancy, there have been extensive preclinical studies examining the molecular signature and hodology of the BNST and their involvement in stress and reward seeking behaviour. This review examines the neurochemical phenotype and connectivity of the BNST, as well as electrophysiological correlates of plasticity in the BNST mediated by stress and/or drugs of abuse.

Substance use outcomes in cocaine-dependent tobacco smokers: A mediation analysis exploring the role of sleep disturbance, craving, anxiety, and depression

BACKGROUND

Sleep disturbance may play a role in cocaine use outcomes and, hence, may be a potential therapeutic target for cocaine use disorder (CUD). Research in this area, which has largely relied on resource-intensive polysomnography, would be facilitated by identifying a self-report sleep measure predictive of CUD outcomes and by a better understanding of the mechanisms by which sleep may impact CUD outcomes. This study tested the predictive validity of the Pittsburgh Sleep Quality Index (PSQI), a self-report assessment of past-month sleep quality. To better understand potential mechanisms, mediation models relating sleep disturbance to CUD outcomes were evaluated.

METHODS

This is a secondary analysis of data from cocaine-dependent (n = 290) participants in a multi-site trial evaluating smoking-cessation treatment for stimulant-dependent patients. The PSQI was collected at baseline; the outcomes of interest were cocaine and drug abstinence at end-of-treatment (weeks 9-10). Potential mediators, measured in weeks 1-8, were: cocaine craving (Brief Substance Craving Scale); and anxiety and depression symptoms (Hospital Anxiety and Depression Scale). Mediation techniques were used to evaluate mediation effects separately and jointly.

RESULTS

The majority of participants (58.3%) had baseline sleep disturbance. Sleep disturbance was not a significant predictor of end-of-treatment abstinence when regressed without consideration of mediators. Cocaine craving, anxiety, and depression were significant mediators, both separately and jointly, of an effect of baseline sleep disturbance on end-of-treatment abstinence.

CONCLUSION

This exploratory analysis suggests that there may be an indirect relationship between self-reported sleep quality and substance use outcomes in cocaine-dependent patients, mediated by craving, anxiety, and depression.

TRIAL REGISTRATION

ClinicalTrials.gov: NCT01077024.

Dorsal BNST α2A-Adrenergic Receptors Produce HCN-Dependent Excitatory Actions That Initiate Anxiogenic Behaviors

Stress is a precipitating agent in neuropsychiatric disease and initiates relapse to drug-seeking behavior in addicted patients. Targeting the stress system in protracted abstinence from drugs of abuse with anxiolytics may be an effective treatment modality for substance use disorders. α_2A-adrenergic receptors (α_2A-ARs) in extended amygdala structures play key roles in dampening stress responses. Contrary to early thinking, α_2A-ARs are expressed at non-noradrenergic sites in the brain. These non-noradrenergic α_2A-ARs play important roles in stress responses, but their cellular mechanisms of action are unclear. In humans, the α_2A-AR agonist guanfacine reduces overall craving and uncouples craving from stress, yet minimally affects relapse, potentially due to competing actions in the brain. Here, we show that heteroceptor α_2A-ARs postsynaptically enhance dorsal bed nucleus of the stria terminalis (dBNST) neuronal activity in mice of both sexes. This effect is mediated by hyperpolarization-activated cyclic nucleotide-gated cation channels because inhibition of these channels is necessary and sufficient for excitatory actions. Finally, this excitatory action is mimicked by clozapine-N-oxide activation of the G_i-coupled DREADD hM4Di in dBNST neurons and its activation elicits anxiety-like behavior in the elevated plus maze. Together, these data provide a framework for elucidating cell-specific actions of GPCR signaling and provide a potential mechanism whereby competing anxiogenic and anxiolytic actions of guanfacine may affect its clinical utility in the treatment of addiction.SIGNIFICANCE STATEMENT Stress affects the development of neuropsychiatric disorders including anxiety and addiction. Guanfacine is an α2A-adrenergic receptor (α2A-AR) agonist with actions in the bed nucleus of the stria terminalis (BNST) that produces antidepressant actions and uncouples stress from reward-related behaviors. Here, we show that guanfacine increases dorsal BNST neuronal activity through actions at postsynaptic α2A-ARs via a mechanism that involves hyperpolarization-activated cyclic nucleotide gated cation channels. This action is mimicked by activation of the designer receptor hM4Di expressed in the BNST, which also induces anxiety-like behaviors. Together, these data suggest that postsynaptic α2A-ARs in BNST have excitatory actions on BNST neurons and that these actions can be phenocopied by the so-called "inhibitory" DREADDs, suggesting that care must be taken regarding interpretation of data obtained with these tools.

Systemic administration of guanfacine improves food-motivated impulsive choice behavior primarily via direct stimulation of postsynaptic α2A-adrenergic receptors in rats

Impulsive choice behavior, which can be assessed using the delay discounting task, is a characteristic of various psychiatric disorders, including attention-deficit/hyperactivity disorder (ADHD). Guanfacine is a selective α_2A-adrenergic receptor agonist that is clinically effective in treating ADHD. However, there is no clear evidence that systemic guanfacine administration reduces impulsive choice behavior in the delay discounting task in rats. In the present study, we examined the effect of systemic guanfacine administration on food-motivated impulsive choice behavior in rats and the neuronal mechanism underlying this effect. Repeated administration of either guanfacine, methylphenidate, or atomoxetine significantly enhanced impulse control, increasing the number of times the rats chose a large but delayed reward in a dose-dependent manner. The effect of guanfacine was significantly blocked by pretreatment with an α_2A-adrenergic receptor antagonist. Furthermore, the effect of guanfacine remained unaffected in rats pretreated with a selective noradrenergic neurotoxin, consistent with a post-synaptic action. In contrast, the effect of atomoxetine on impulsive choice behavior was attenuated by pretreatment with the noradrenergic neurotoxin. These results provide the first evidence that systemically administered guanfacine reduces impulsive choice behavior in rats and that direct stimulation of postsynaptic, rather than presynaptic, α_2A-adrenergic receptors is involved in this effect.

α2A -Adrenergic receptor polymorphisms and mRNA expression levels are associated with delay discounting in cocaine users

Cocaine users characteristically display preferences for smaller immediate rewards over larger delayed rewards, and this delay discounting (DD) has been proposed as an endophenotype of cocaine addiction. Recent evidence suggests that the norepinephrine system and more specifically the α_2A -adrenergic receptor (ADRA2A) are impacted by chronic cocaine use while also being potentially involved in the neural mechanisms underlying DD. Hence, we investigated the effects of ADRA2A polymorphisms and ADRA2A mRNA expression levels on DD of cocaine users and stimulant-naïve controls. Two hundred and twenty-three participants (129 cocaine users and 94 stimulant-naïve healthy controls) completed a computerized DD paradigm and were genotyped for three single nucleotide polymorphisms (SNPs; rs1800544, rs521674 and rs602618) in the ADRA2A gene, while their peripheral ADRA2A mRNA expression was quantified in whole blood samples. The three SNPs were in near-perfect linkage disequilibrium. Accordingly, significant group*genotype interactions were found for all three ADRA2A variants revealing steeper DD in cocaine users (but not in controls) carrying the G-allele of SNP rs1800544, the T-allele of rs521674 and the C-allele of rs602618. Similarly, high ADRA2A mRNA expression levels were significantly associated with a reduced tendency to choose smaller more immediate rewards (over larger delayed rewards) in cocaine users but not in controls. As the relationship between DD and cocaine use was moderated by ADRA2A SNPs and by peripheral ADRA2A gene expression, we propose that the norepinephrine system is involved in DD deficits observed in cocaine using individuals. Consequently, pharmacological compounds targeting ADRA2As might be considered for the symptom-specific treatment of delay aversion in stimulant addiction.

The individual and combined effects of phenmetrazine and mgluR2/3 agonist LY379268 on the motivation to self-administer cocaine

BACKGROUND

The US Food and Drug Administration has not approved a treatment for cocaine addiction, possibly due in part to the fact that repeated cocaine use results in dysregulation of multiple neurotransmitter systems, including glutamate and dopamine, and an emergence of increased negative affective states and heightening motivation to take cocaine despite negative consequences. We used a combination therapy approach to assess whether modulation of both glutamate and dopamine transmission would reduce the motivation to self- administer cocaine compared to modulation of either system alone.

METHODS

The metabotropic glutamate 2/3 receptor agonist, LY379268, and the monoamine releaser, phenmetrazine, were used to assess their individual and combined ability to decrease the reinforcing efficacy of cocaine because they modulate glutamate and dopamine levels, respectively. Cocaine breakpoints and cocaine intake was assessed, using a progressive ratio schedule, at baseline in three groups based on dose of cocaine (0.19, 0.38, 0.75mg/kg/infusion), and following LY379268 (0.03 or 0.30mg/kg; i.p.), phenmetrazine (25mg/kg/day; osmotic minipump), and a combination of the two drugs.

RESULTS

LY379268 and phenmetrazine alone reduced breakpoints for all doses of cocaine. The combination of the two drugs showed a concerted effect in reducing breakpoints for all doses of cocaine, with the lowest dose of cocaine reduced by as much as 70%.

CONCLUSIONS

These data support combination therapy of dopamine and glutamate systems as an effective means to reduce the motivation to take cocaine since a combination of drugs can address neurobiological dysfunction in multiple neurotransmitter systems compared to therapies using single drugs.

The Involvement of Norepinephrine in Behaviors Related to Psychostimulant Addiction

Although it is generally accepted that the abuse-related effects of amphetamines and cocaine result from the activation of the brain dopaminergic (DA) system, the psychostimulants also alter other neurotransmitter systems. In particular, they increase extracellular levels of norepinephrine (NE) and serotonin by inhibiting respective plasma membrane transporters and/or inducing release. The present review will discuss the preclinical findings on the effects of the NE system modulation (lesions, pharmacological and genetic approaches) on behaviors (locomotor hyperactivity, behavioral sensitization, modification of intracranial self-stimulation, conditioned place preference, drug self-administration, extinction/reinstatement of drug seeking behavior) related to the psychostimulant addiction.

Switch from excitatory to inhibitory actions of ethanol on dopamine levels after chronic exposure: Role of kappa opioid receptors

Acute ethanol exposure is known to stimulate the dopamine system; however, chronic exposure has been shown to downregulate the dopamine system. In rodents, chronic intermittent exposure (CIE) to ethanol also increases negative affect during withdrawal, such as, increases in anxiety- and depressive-like behavior. Moreover, CIE exposure results in increased ethanol drinking and preference during withdrawal. Previous literature documents reductions in CIE-induced anxiety-, depressive-like behaviors and ethanol intake in response to kappa opioid receptor (KOR) blockade. KORs are located on presynaptic dopamine terminals in the nucleus accumbens (NAc) and inhibit release, an effect which has been linked to negative affective behaviors. Previous reports show an upregulation in KOR function following extended CIE exposure; however it is not clear whether there is a direct link between KOR upregulation and dopamine downregulation during withdrawal from CIE. This study aimed to examine the effects of KOR modulation on dopamine responses to ethanol of behaving mice exposed to air or ethanol vapor in a repeated intermittent pattern. First, we showed that KORs have a greater response to an agonist after moderate CIE compared to air exposed mice using ex vivo fast scan cyclic voltammetry. Second, using in vivo microdialysis, we showed that, in contrast to the expected increase in extracellular levels of dopamine following an acute ethanol challenge in air exposed mice, CIE exposed mice exhibited a robust decrease in dopamine levels. Third, we showed that blockade of KORs reversed the aberrant inhibitory dopamine response to ethanol in CIE exposed mice while not affecting the air exposed mice demonstrating that inhibition of KORs "rescued" dopamine responses in CIE exposed mice. Taken together, these findings indicate that augmentation of dynorphin/KOR system activity drives the reduction in stimulated (electrical and ethanol) dopamine release in the NAc. Thus, blockade of KORs is a promising avenue for developing pharmacotherapies for alcoholism.

Stress-Induced Reinstatement of Drug Seeking: 20 Years of Progress

In human addicts, drug relapse and craving are often provoked by stress. Since 1995, this clinical scenario has been studied using a rat model of stress-induced reinstatement of drug seeking. Here, we first discuss the generality of stress-induced reinstatement to different drugs of abuse, different stressors, and different behavioral procedures. We also discuss neuropharmacological mechanisms, and brain areas and circuits controlling stress-induced reinstatement of drug seeking. We conclude by discussing results from translational human laboratory studies and clinical trials that were inspired by results from rat studies on stress-induced reinstatement. Our main conclusions are (1) The phenomenon of stress-induced reinstatement, first shown with an intermittent footshock stressor in rats trained to self-administer heroin, generalizes to other abused drugs, including cocaine, methamphetamine, nicotine, and alcohol, and is also observed in the conditioned place preference model in rats and mice. This phenomenon, however, is stressor specific and not all stressors induce reinstatement of drug seeking. (2) Neuropharmacological studies indicate the involvement of corticotropin-releasing factor (CRF), noradrenaline, dopamine, glutamate, kappa/dynorphin, and several other peptide and neurotransmitter systems in stress-induced reinstatement. Neuropharmacology and circuitry studies indicate the involvement of CRF and noradrenaline transmission in bed nucleus of stria terminalis and central amygdala, and dopamine, CRF, kappa/dynorphin, and glutamate transmission in other components of the mesocorticolimbic dopamine system (ventral tegmental area, medial prefrontal cortex, orbitofrontal cortex, and nucleus accumbens). (3) Translational human laboratory studies and a recent clinical trial study show the efficacy of alpha-2 adrenoceptor agonists in decreasing stress-induced drug craving and stress-induced initial heroin lapse.

Adolescent exposure to cocaine increases anxiety-like behavior and induces morphologic and neurochemical changes in the hippocampus of adult rats

Repeated exposure to cocaine during adolescence may affect both physical and psychological conditions in the brain, and increase the risk of psychiatric disorders and addiction behaviors in adulthood. Adolescence represents a critical development period for the hippocampus. Moreover, different regions of the hippocampus are involved in different functions. Dorsal hippocampus (dHP) has been implicated in learning and memory, whereas ventral hippocampus (vHP) plays an important role in emotional processing. In this study, the rats that were exposed to cocaine during adolescence (postnatal days, P28-P42) showed higher anxiety-like behavior in the elevated plus maze test in adulthood (P80), but displayed normal spatial learning and memory in the Morris water maze test. Furthermore, repeated exposure to cocaine during adolescence lead to alterations in morphology of pyramidal neurons, activities of astrocytes, and levels of proteins that involved in synaptic transmission, apoptosis, inflammation and addiction in both dHP and vHP of adult rats. These findings suggest that repeated exposure to cocaine during adolescence in rats may elicit morphologic and neurochemical changes in the hippocampus when the animals reach adulthood. These changes may contribute to the increased susceptibility for psychiatric disorders and addiction seen in adults.

Vagus Nerve Stimulation as a Tool to Induce Plasticity in Pathways Relevant for Extinction Learning

Extinction describes the process of attenuating behavioral responses to neutral stimuli when they no longer provide the reinforcement that has been maintaining the behavior. There is close correspondence between fear and human anxiety, and therefore studies of extinction learning might provide insight into the biological nature of anxiety-related disorders such as post-traumatic stress disorder, and they might help to develop strategies to treat them. Preclinical research aims to aid extinction learning and to induce targeted plasticity in extinction circuits to consolidate the newly formed memory. Vagus nerve stimulation (VNS) is a powerful approach that provides tight temporal and circuit-specific release of neurotransmitters, resulting in modulation of neuronal networks engaged in an ongoing task. VNS enhances memory consolidation in both rats and humans, and pairing VNS with exposure to conditioned cues enhances the consolidation of extinction learning in rats. Here, we provide a detailed protocol for the preparation of custom-made parts and the surgical procedures required for VNS in rats. Using this protocol we show how VNS can facilitate the extinction of conditioned fear responses in an auditory fear conditioning task. In addition, we provide evidence that VNS modulates synaptic plasticity in the pathway between the infralimbic (IL) medial prefrontal cortex and the basolateral complex of the amygdala (BLA), which is involved in the expression and modulation of extinction memory.

Effects of abstinence from chronic cocaine self-administration on nonhuman primate dorsal and ventral noradrenergic bundle terminal field structures

Repeated exposure to cocaine is known to dysregulate the norepinephrine system, and norepinephrine has also been implicated as having a role in abstinence and withdrawal. The goal of this study was to determine the effects of exposure to cocaine self-administration and subsequent abstinence on regulatory elements of the norepinephrine system in the nonhuman primate brain. Rhesus monkeys self-administered cocaine (0.3 mg/kg/injection, 30 reinforcers/session) under a fixed-interval 3-min schedule of reinforcement for 100 sessions. Animals in the abstinence group then underwent a 30-day period during which no operant responding was conducted, followed by a final session of operant responding. Control animals underwent identical schedules of food reinforcement and abstinence. This duration of cocaine self-administration has been shown previously to increase levels of norepinephrine transporters (NET) in the ventral noradrenergic bundle terminal fields. In contrast, in the current study, abstinence from chronic cocaine self-administration resulted in elevated levels of [(3)H]nisoxetine binding to the NET primarily in dorsal noradrenergic bundle terminal field structures. As compared to food reinforcement, chronic cocaine self-administration resulted in decreased binding of [(3)H]RX821002 to α2-adrenoceptors primarily in limbic-related structures innervated by both dorsal and ventral bundles, as well as elevated binding in the striatum. However, following abstinence from responding for cocaine binding to α2-adrenoceptors was not different than in control animals. These data demonstrate the dynamic nature of the regulation of norepinephrine during cocaine use and abstinence, and provide further evidence that the norepinephrine system should not be overlooked in the search for effective pharmacotherapies for cocaine dependence.

Convergent pharmacological mechanisms in impulsivity and addiction: insights from rodent models

Research over the last two decades has widely demonstrated that impulsivity, in its various forms, is antecedent to the development of drug addiction and an important behavioural trait underlying the inability of addicts to refrain from continued drug use. Impulsivity describes a variety of rapidly and prematurely expressed behaviours that span several domains from impaired response inhibition to an intolerance of delayed rewards, and is a core symptom of attention deficit hyperactivity disorder (ADHD) and other brain disorders. Various theories have been advanced to explain how impulsivity interacts with addiction both causally and as a consequence of chronic drug abuse; these acknowledge the strong overlaps in neural circuitry and mechanisms between impulsivity and addiction and the seemingly paradoxical treatment of ADHD with stimulant drugs with high abuse potential. Recent years have witnessed unprecedented progress in the elucidation of pharmacological mechanisms underpinning impulsivity. Collectively, this work has significantly improved the prospect for new therapies in ADHD as well as our understanding of the neural mechanisms underlying the shift from recreational drug use to addiction. In this review, we consider the extent to which pharmacological interventions that target impulsive behaviour are also effective in animal models of addiction. We highlight several promising examples of convergence based on empirical findings in rodent-based studies.

Vagus nerve stimulation enhances extinction of conditioned fear and modulates plasticity in the pathway from the ventromedial prefrontal cortex to the amygdala

Fearful experiences can produce long-lasting and debilitating memories. Extinction of the fear response requires consolidation of new memories that compete with fearful associations. Subjects with posttraumatic stress disorder (PTSD) show impaired extinction of conditioned fear, which is associated with decreased ventromedial prefrontal cortex (vmPFC) control over amygdala activity. Vagus nerve stimulation (VNS) enhances memory consolidation in both rats and humans, and pairing VNS with exposure to conditioned cues enhances the consolidation of extinction learning in rats. Here we investigated whether pairing VNS with extinction learning facilitates plasticity between the infralimbic (IL) medial prefrontal cortex and the basolateral complex of the amygdala (BLA). Rats were trained on an auditory fear conditioning task, which was followed by a retention test and 1 day of extinction training. Vagus nerve stimulation or sham-stimulation was administered concurrently with exposure to the fear-conditioned stimulus and retention of fear conditioning was tested again 24 h later. Vagus nerve stimulation-treated rats demonstrated a significant reduction in freezing after a single extinction training session similar to animals that received 5× the number of extinction pairings. To study plasticity in the IL-BLA pathway, we recorded evoked field potentials (EFPs) in the BLA in anesthetized animals 24 h after retention testing. Brief burst stimulation in the IL produced LTD in the BLA field response in fear-conditioned and sham-treated animals. In contrast, the same stimulation resulted in potentiation of the IL-BLA pathway in the VNS-treated group. The present findings suggest that VNS promotes plasticity in the IL-BLA pathway to facilitate extinction of conditioned fear responses (CFRs).

α(2A)-adrenergic receptors filter parabrachial inputs to the bed nucleus of the stria terminalis

α2-adrenergic receptors (AR) within the bed nucleus of the stria terminalis (BNST) reduce stress-reward interactions in rodent models. In addition to their roles as autoreceptors, BNST α(2A)-ARs suppress glutamatergic transmission. One prominent glutamatergic input to the BNST originates from the parabrachial nucleus (PBN) and consists of asymmetric axosomatic synapses containing calcitonin gene-related peptide (CGRP) and vGluT2. Here we provide immunoelectron microscopic data showing that many asymmetric axosomatic synapses in the BNST contain α(2A)-ARs. Further, we examined optically evoked glutamate release ex vivo in BNST from mice with virally delivered channelrhodopsin2 (ChR2) expression in PBN. In BNST from these animals, ChR2 partially colocalized with CGRP, and activation generated EPSCs in dorsal anterolateral BNST neurons that elicited two cell-type-specific outcomes: (1) feedforward inhibition or (2) an EPSP that elicited firing. We found that the α(2A)-AR agonist guanfacine selectively inhibited this PBN input to the BNST, preferentially reducing the excitatory response in ex vivo mouse brain slices. To begin to assess the overall impact of α(2A)-AR control of this PBN input on BNST excitatory transmission, we used a Thy1-COP4 mouse line with little postsynaptic ChR2 expression nor colocalization of ChR2 with CGRP in the BNST. In slices from these mice, we found that guanfacine enhanced, rather than suppressed, optogenetically initiated excitatory drive in BNST. Thus, our study reveals distinct actions of PBN afferents within the BNST and suggests that α(2A)-AR agonists may filter excitatory transmission in the BNST by inhibiting a component of the PBN input while enhancing the actions of other inputs.

Cocaine self-administration and extinction alter medullary noradrenergic and limbic forebrain cFos responses to acute, noncontingent cocaine injections in adult rats

Central noradrenergic (NA) signaling contributes critically to multiple behavioral effects of cocaine administration, particularly stress- and anxiety-related effects. The present study examined the ability of acute cocaine to induce the immediate early gene product, cFos, in NA neurons and stress-related neural circuits in rats that were cocaine-naïve, or had a history of cocaine self-administration with or without extinction. Rats implanted with jugular catheters were trained to self-administer cocaine (0.5-mg/kg/infusion), with a subset subsequently trained on extinction. Cocaine-naïve controls were handled daily. After a final day of self-administration, extinction, or handling, rats received an i.p. injection of either cocaine (20-mg/kg) or saline, and 90min later were anesthetized and perfused. Tissue sections were processed for immunoperoxidase labeling of nuclear cFos with either immunoperoxidase or immunofluorescent cytoplasmic labeling of dopamine beta hydroxylase or tyrosine hydroxylase. Acute cocaine increased the number of activated NA neurons within the caudal nucleus of the solitary tract (NTS; A2 cell group) in cocaine-naïve and extinguished rats, but not in rats that only self-administered. Extinction attenuated cocaine-induced cFos activation in NA neurons of the caudal ventrolateral medulla (A1/C1 cell groups), and attenuated cFos within the paraventricular nucleus of the hypothalamus, the apex of the central neuroendocrine stress axis. Cocaine consistently increased cFos in the bed nucleus of the stria terminalis, regardless of history. NA neurons of the locus coeruleus (A6 cell group) were not activated after cocaine administration in any experimental group. Thus, the ability of cocaine to activate central stress circuitry is altered after cocaine self-administration. Our results suggest a unique role for the NTS in cocaine-induced reinstatement, as extinction training enhanced the ability of cocaine to activate NA neurons within this region. These findings suggest central NA systems originating in the caudal brainstem as potential targets for the treatment of cocaine addiction.

Long-term effects of chronic cocaine exposure throughout adolescence on anxiety and stress responsivity in a Wistar rat model

Adolescents display increased vulnerability to engage in drug experimentation. This is often considered a risk factor for later drug abuse. In this scenario, the permanent effects of cocaine exposure during adolescence on anxiety levels and stress responsivity, which may result in behavioral phenotypes prone to addiction, are now starting to be unveiled. Thus, the purpose of the present study was to evaluate the long-lasting effects of chronic cocaine administration during adolescence, on anxiety-like behavior and on stress response. Adolescent male Wistar rats were daily administered 45-mg cocaine/kg of body weight in three equal intraperitoneal doses with 1-h interval, from postnatal day (PND) 35 to 50. The effects of cocaine administration on anxiety levels, assessed in the Elevated Plus Maze (EPM), and on social stress response, assessed in the resident-intruder paradigm (R/I), were evaluated 10 days after withdrawal, when rats were reaching the adulthood. The underlying dopaminergic activity, and the corticosterone and testosterone levels were determined. Our results showed that cocaine induced long-lasting alterations in the hypothalamus-pituitary-adrenals (HPA) axis function and in testosterone levels. Such alterations resulted in significant and enduring changes in behavioral responses to environmental challenges, such as the EPM and R/I, including the evaluation of potential threats that may lead to high-risk behavior and low-benefit choices. This was further supported by an altered dopaminergic function in the amygdala and hippocampus. The present findings provide new insights into how the use of cocaine during adolescent development may modulate emotional behavior later in life. Compromised ability to recognize and deal with potential threats is an important risk factor to perpetuate compulsive drug seeking and relapse susceptibility.

Adrenaline rush: the role of adrenergic receptors in stimulant-induced behaviors

Psychostimulants, such as cocaine and amphetamines, act primarily through the monoamine neurotransmitters dopamine (DA), norepinephrine, and serotonin. Although stimulant addiction research has largely focused on DA, medication development efforts targeting the dopaminergic system have thus far been unsuccessful, leading to alternative strategies aimed at abating stimulant abuse. Noradrenergic compounds have shown promise in altering the behavioral effects of stimulants in rodents, nonhuman primates, and humans. In this review, we discuss the contribution of each adrenergic receptor (AR) subtype (α1, α2, and β) to five stimulant-induced behaviors relevant to addiction: locomotor activity, conditioned place preference, anxiety, discrimination, and self-administration. AR manipulation has diverse effects on these behaviors; each subtype profoundly influences outcomes in some paradigms but is inconsequential in others. The functional neuroanatomy and intracellular signaling mechanisms underlying the impact of AR activation/blockade on these behaviors remain largely unknown, presenting a new frontier for research on psychostimulant-AR interactions.

Short-term abstinence from cocaine self-administration, but not passive cocaine infusion, elevates αCaMKII autophosphorylation in the rat nucleus accumbens and medial prefrontal cortex

Increases in alpha calcium/calmodulin-dependent protein kinase type II (αCaMKII) activity in the nucleus accumbens shell has been proposed as a core component in the motivation to self-administer cocaine and in priming-induced drug-seeking. Since cocaine withdrawal promotes drug-seeking, we hypothesized that abstinence from cocaine self-administration should enhance αCaMKII as well. We found that short-term abstinence from contingent, but not non-contingent, cocaine i.v. self-administration (2 h/d for 14 d; 0.25 mg/0.1 ml, 6 s infusion) elevates αCaMKII autophosphorylation, but not the kinase expression, in a dynamic, time- and brain region-dependent manner. Increased αCaMKII autophosphorylation in the nucleus accumbens (NAc) and medial prefrontal cortex (mPFC), but not dorsolateral striatum (dlS), was found 24 h, but not immediately, after the last cocaine self-administration session. Notably, in the mPFC, but not NAc and dlS, αCaMKII autophosphorylation was still enhanced 7 d later. The persistent enhancement in the mPFC of abstinent rats may represent a previously unappreciated contribution to initial incubation of cocaine-seeking.

The role of guanfacine as a therapeutic agent to address stress-related pathophysiology in cocaine-dependent individuals

The pathophysiology of cocaine addiction is linked to changes within neural systems and brain regions that are critical mediators of stress system sensitivity and behavioral processes associated with the regulation of adaptive goal-directed behavior. This is characterized by the upregulation of core adrenergic and corticotropin-releasing factor mechanisms that subserve negative affect and anxiety and impinge upon intracellular pathways in the prefrontal cortex underlying cognitive regulation of stress and negative emotional state. Not only are these mechanisms essential to the severity of cocaine withdrawal symptoms, and hence the trajectory of clinical outcome, but also they may be particularly pertinent to the demography of cocaine dependence. The ability of guanfacine to target overlapping stress, reward, and anxiety pathophysiology suggests that it may be a useful agent for attenuating the stress- and cue-induced craving state not only in women but also in men. This is supported by recent research findings from our own laboratory. Additionally, the ability of guanfacine to improve regulatory mechanisms that are key to exerting cognitive and emotional control over drug-seeking behavior also suggests that guanfacine may be an effective medication for reducing craving and relapse vulnerability in many drugs of abuse. As cocaine-dependent individuals are typically polydrug abusers and women may be at a greater disadvantage for compulsive drug use than men, it is plausible that medications that target catecholaminergic frontostriatal inhibitory circuits and simultaneously reduce stress system arousal may provide added benefits for attenuating cocaine dependence.

The effects of varied extinction procedures on contingent cue-induced reinstatement in Sprague-Dawley rats

RATIONALE

Cue exposure therapy, which attempts to limit relapse by reducing reactivity to cocaine-paired cues through repeated exposures, has had limited success.

OBJECTIVES

The current experiments examined cocaine cue-induced anxiogenesis and investigated whether a model of cue exposure therapy would reduce reinstatement of cocaine seeking in rats with a history of cocaine self-administration.

METHODS

Male rats experienced daily intravenous cocaine self-administration. Rats then experienced exposure to either the self-administration context or the context plus noncontingent presentations of cocaine-paired cues. Immediately following exposure, anxiety-like behavior was measured using elevated plus maze and defensive burying tests. In a second group of rats, self-administration was followed by 7 days of exposure to the context, context + noncontingent cue exposure, lever extinction, or cue + lever extinction. All animals then underwent two contingent cue-induced reinstatement tests separated by 7 days of lever extinction.

RESULTS

Exposure to noncontingent cocaine-paired cues in the self-administration context increased anxiety-like behavior on the defensive burying test. Animals that experienced lever + cue extinction displayed the least cocaine seeking on the first reinstatement test, and lever extinction reduced cocaine seeking below context exposure or context + noncontingent cue exposure. All animals had similar levels of cocaine seeking on the second reinstatement test.

CONCLUSION

Noncontingent cue exposure causes anxiety, and noncontingent cue and context exposure are less effective at reducing contingent cue-induced reinstatement than lever or lever + cue extinction. These data indicate that active extinction of the drug-taking response may be critical for reduction of relapse proclivity in former cocaine users.

Elevated Norepinephrine may be a Unifying Etiological Factor in the Abuse of a Broad Range of Substances: Alcohol, Nicotine, Marijuana, Heroin, Cocaine, and Caffeine

A wide range of commonly abused drugs have effects on the noradrenergic neurotransmitter system, including alterations during acute intoxication and chronic use of these drugs. It is not established, however, that individual differences in noradrenergic signaling, which may be present prior to use of drugs, predispose certain persons to substance abuse. This paper puts forth the novel hypothesis that elevated noradrenergic signaling, which may be raised largely due to genetics but also due to environmental factors, is an etiological factor in the abuse of a wide range of substances, including alcohol, nicotine, marijuana, heroin, cocaine, and caffeine. Data are reviewed for each of these drugs comprising their interaction with norepinephrine during acute intoxication, long-term use, subsequent withdrawal, and stress-induced relapse. In general, the data suggest that these drugs acutely boost noradrenergic signaling, whereas long-term use also affects this neurotransmitter system, possibly suppressing it. During acute withdrawal after chronic drug use, noradrenergic signaling tends to be elevated, consistent with the observation that norepinephrine lowering drugs such as clonidine reduce withdrawal symptoms. Since psychological stress can promote relapse of drug seeking in susceptible individuals and stress produces elevated norepinephrine release, this suggests that these drugs may be suppressing noradrenergic signaling during chronic use or instead elevating it only in reward circuits of the brain. If elevated noradrenergic signaling is an etiological factor in the abuse of a broad range of substances, then chronic use of pharmacological agents that reduce noradrenergic signaling, such as clonidine, guanfacine, lofexidine, propranolol, or prazosin, may help prevent or treat drug abuse in general.

An open-label study of guanfacine extended release for traumatic stress related symptoms in children and adolescents

OBJECTIVE

The purpose of this open-label pilot study was to investigate the effectiveness and tolerability of guanfacine extended release (GXR) 1-4 mg given in the evening, on the symptoms of traumatic stress (reexperiencing, avoidance, overarousal), generalized anxiety, and functional impairment in children and adolescents with a history of traumatic stress with or without posttraumatic stress disorder (PTSD). As many of our sample had associated attention-deficit/hyperactivity disorder (ADHD) symptoms, we also assessed whether the presence of traumatic stress symptoms impaired the effectiveness of GXR in the treatment of comorbid ADHD symptoms.

METHODS

Participants were 19 children and adolescents 6-18 years of age, with current traumatic stress symptoms. In an 8 week open-label design, each patient's scores on parent-, child-, and clinician-reported symptom rating scales assessing traumatic stress symptoms, generalized anxiety, ADHD symptoms, functional impairment, and global symptom severity and improvement (n=17) were evaluated off and on GXR using χ(2) goodness-of-fit tests, paired t tests, and repeated measures analyses of variance (ANOVAs). To examine patterns of change in outcome measures across treatment, MPlus software was used to conduct linear growth curves modeled with individual-varying times of observation (i.e., random slopes).

RESULTS

Using an average GXR daily dose of 1.19 mg±0.35 mg and an average weight-adjusted daily dose of 0.03 mg/kg±0.01 mg/kg, significant differences were found on all symptom severity measures. Parent reported UCLA Reaction Index scores assessing cluster B (reexperiencing), C (avoidant), and D (overarousal) symptoms significantly improved. In the presence of PTSD symptoms, children with ADHD experienced significantly improved ADHD symptom scores, suggesting that comorbidity does not attenuate an ADHD symptom response to GXR therapy. Medication was generally well tolerated.

CONCLUSIONS

Within the limits of an open-label, hypothesis-generating pilot study, our results suggest that the α2A-adrenoceptor agonist GXR may have therapeutic effects in the treatment of PTSD symptoms in traumatically stressed children and adolescents. The effective dose may be lower than that found for ADHD. Our pilot study supports the need for further controlled research on the effects of GXR and other α2A-adrenoceptor agonists in pediatric disorders of traumatic stress.

Noradrenergic control of the bed nucleus of the stria terminalis in stress and reward

The bed nucleus of the stria terminalis (BNST) is a group of inter-connected subnuclei that play critical roles in stress-reward interactions. An interesting feature of this brain region is the massive noradrenergic input that it receives. Important roles for norepinephrine in this region have been documented in a number of stress and reward related behaviors. This work has been paralleled over the last several years by efforts to understand the actions of norepinephrine on neuronal function in the region. In this review, we will summarize the current state of these research areas.

Yohimbine increases opioid-seeking behavior in heroin-dependent, buprenorphine-maintained individuals

RATIONALE

In laboratory animals, the biological stressor yohimbine (α(2)-noradrenergic autoreceptor antagonist) promotes drug seeking. Human laboratory studies have demonstrated that psychological stressors can increase drug craving but not that stressors alter drug seeking.

OBJECTIVES

This clinical study tested whether yohimbine increases opioid-seeking behavior.

METHODS

Ten heroin-dependent, buprenorphine-stabilized (8 mg/day) volunteers sampled two doses of hydromorphone [12 and 24 mg IM in counterbalanced order, labeled drug A (session 1) and drug B (session 2)]. During each of six later sessions (within-subject, double-blind, randomized crossover design), volunteers could respond on a 12-trial choice progressive ratio task to earn units (1 or 2 mg) of the sampled hydromorphone dose (drug A or B) vs money ($2) following different oral yohimbine pretreatment doses (0, 16.2, and 32.4 mg).

RESULTS

Behavioral economic demand intensity and peak responding (O (max)) were significantly higher for hydromorphone 2 than 1 mg. Relative to placebo, yohimbine significantly increased hydromorphone demand inelasticity, more so for hydromorphone 1-mg units (P (max) = 909, 3,647, and 3,225 for placebo, 16.2, and 32.4 mg yohimbine doses, respectively) than hydromorphone 2-mg units (P (max) = 2,656, 3,193, and 3,615, respectively). Yohimbine produced significant but clinically modest dose-dependent increases in blood pressure (systolic ≈ 15 and diastolic ≈ 10 mmHg) and opioid withdrawal symptoms, and decreased opioid agonist symptoms and elated mood.

CONCLUSIONS

These findings concur with preclinical data by demonstrating that yohimbine increases drug seeking; in this study, these effects occurred without clinically significant subjective distress or elevated craving, and partly depended on opioid unit dose.

The region-specific activation of Ca2+/calmodulin dependent protein kinase II and extracellular signal-regulated kinases in hippocampus following chronic alcohol exposure

Previous studies suggest that hippocampal CA1, CA3, and DG regions may have distinct roles in alcohol dependence. Extracellular signal-regulated kinases (ERKs) and Ca(2+)/calmodulin dependent protein kinase II (CaMKII) have been shown to contribute to the molecular mechanism underlying drug dependence and relapse, and there may be an interaction between the activation of ERKs and CaMKII. However, little is known regarding the mechanisms underlying the effects of alcohol exposure, withdrawal, and relapse, particularly with regard to the interaction between CaMKII and ERK1/2 signaling in hippocampal subregions. In the present study, rats were provided water containing 6% alcohol as their only drinking source. We found that alcohol exerted locomotor stimulant and anxiolytic effects on rats in open field behaviors. Following chronic alcohol exposure, phospho-ERK1/2 was significantly decreased in the DG. Alcohol withdrawal was associated with an increase of phospho-ERK1/2 in the CA1 and DG, while alcohol re-exposure induced a decrease of phospho-ERK1/2 in the CA1, CA3, and DG. The activation of CaMKII (Thr286) correlated with the effects of alcohol on phospho-ERK1/2. Our results indicate that region-specific activation CaMKII-ERK1/2 signaling in the hippocampal CA1 and DG may play an important role in alcohol dependence.