Sex and estrogen influence drug abuse

The role of β-Nicotyrine in E-Cigarette abuse liability I: Drug Discrimination

Background

β-Nicotyrine (β-Nic) is a unique minor alkaloid constituent in electronic nicotine delivery systems (ENDS) that is derived from nicotine (Nic) degradation and can reach 25% of Nic concentrations in ENDS aerosol. β-Nic slows Nic metabolism and prolongs systemic Nic exposure, which may alter the discriminability of Nic. The present study sought to examine β-Nic has interoceptive effects itself, and if it alters the subjective effects ENDS products within a drug-discrimination paradigm.

Methods

The pharmacodynamics of β-Nic were examined in vitro, and a nicotine discrimination paradigm was used to determine if β-Nic (0 - 5.0 mg/kg) shares discriminative stimulus properties with Nic (0.2 mg/kg) in male (n = 13) and female (n = 14) rats after 10- & 60-min β-Nic pretreatment delays. A second group of rats was trained to discriminate β-Nic and Nornicotine (Nornic) from saline to determine if β-Nic alone has interoceptive properties and whether they are similar to Nornic.

Results

β-Nic had similar binding affinity and efficacy at the α4β2 nicotinic receptor subtype as Nornic, ~50% of Nic efficacy. However, β-Nic only weakly substituted for Nic during substitution testing in female rats, but not males, whereas Nornic fully substituted for Nic. Combination testing at the 10 and 60-min pretreatment intervals showed that β-Nic dose-dependently increased the duration of nicotine's discriminative stimulus effects, especially at the 60-min delay. Drug naïve rats could reliably discriminate Nornic, but not β-Nic, from Sal.

Conclusion

β-Nic increased and prolonged the interoceptive stimulus properties of Nic, suggesting it may alter to the abuse liability of ENDS through its ability to slow Nic metabolism.

Effects of acute and chronic methylphenidate on prepulse inhibition: A sex difference study in Wistar rats

BACKGROUND

The utilization of methylphenidate (MPH) is experiencing a notable surge within the adult population. This growth can be attributed to two key factors: its recreational and cognitive enhancement purposes, as well as the rising prevalence of ADHD diagnoses within this population. This study examined acute and chronic oral MPH effects on attention in male and female Wistar rats. To this end, we used a prepulse inhibition (PPI) task, which is widely used to assess psychoactive drug effects in both humans and rodents. This task allowed us to evaluate changes in attention by analyzing sensorimotor gating associated with stimulus selection process.

METHODS

Animals were administered a clinically relevant dose of MPH (5 mg/kg) daily for seven days. The estrous cycle phases of the female rats were measured during behavioral sessions. The PPI task was conducted 20 min after drug administration on day 1 (acute), day 7 (chronic), and 48 h post-treatment.

RESULTS

Results indicated that both acute and chronic MPH treatment impaired PPI expression in male rats, but not in female rats, regardless of their estrous cycle phase. Furthermore, a differential effect of chronic MPH treatment on the PPI task was found in male rats. Specifically, on the seventh treatment day, the PPI effect was observed when animals undertook the PPI task for the first time but was impaired in those animals in which the initial PPI session occurred under the acute influence of the drug (day 1).

CONCLUSIONS

These findings suggest that the impact of MPH on sensorimotor gating responses may vary based on sex and task experience, possibly leading to state-dependent effects in healthy individuals.

Estradiol and Mu opioid-mediated reward: The role of estrogen receptors in opioid use

Opioid use and opioid use disorder are characterized by sex and gender differences, and some of these differences may be mediated by differences in the hormonal milieu within and across individuals. This review focuses on the role of ovarian hormones, and particularly estradiol, on the endogenous mu opioid receptor system. There is an abundance of data indicating that estradiol influences the activity of endogenous mu opioid peptides, the activation of mu opioid receptors, and the internalization and desensitization of mu opioid receptors. These effects have functional consequences on behaviors mediated by endogenous mu opioid receptor activity and on sensitivity to mu opioid agonists and antagonists. Recent behavioral data suggest these consequences extend to mu opioid reward, and preclinical studies report that estradiol decreases self-administration of mu opioid receptor agonists across a range of experimental conditions. Data collected in human laboratory studies suggest that estradiol may have functionally similar effects in clinical populations, and thus estrogen receptors may be a potential target in the development of novel therapeutics. This review summarizes data from cellular assays to clinical trials to explore how estradiol influences mu opioid receptor activity, as well as potential ways in which estrogen receptors may be targeted to address the problems of opioid use.

Oxycodone: A Current Perspective on Its Pharmacology, Abuse, and Pharmacotherapeutic Developments

Oxycodone, a semisynthetic derivative of naturally occurring thebaine, an opioid alkaloid, has been available for more than 100 years. Although thebaine cannot be used therapeutically due to the occurrence of convulsions at higher doses, it has been converted to a number of other widely used compounds that include naloxone, naltrexone, buprenorphine, and oxycodone. Despite the early identification of oxycodone, it was not until the 1990s that clinical studies began to explore its analgesic efficacy. These studies were followed by the pursuit of several preclinical studies to examine the analgesic effects and abuse liability of oxycodone in laboratory animals and the subjective effects in human volunteers. For a number of years oxycodone was at the forefront of the opioid crisis, playing a significant role in contributing to opioid misuse and abuse, with suggestions that it led to transitioning to other opioids. Several concerns were expressed as early as the 1940s that oxycodone had significant abuse potential similar to heroin and morphine. Both animal and human abuse liability studies have confirmed, and in some cases amplified, these early warnings. Despite sharing a similar structure with morphine and pharmacological actions also mediated by the μ-opioid receptor, there are several differences in the pharmacology and neurobiology of oxycodone. The data that have emerged from the many efforts to analyze the pharmacological and molecular mechanism of oxycodone have generated considerable insight into its many actions, reviewed here, which, in turn, have provided new information on opioid receptor pharmacology. SIGNIFICANCE STATEMENT: Oxycodone, a μ-opioid receptor agonist, was synthesized in 1916 and introduced into clinical use in Germany in 1917. It has been studied extensively as a therapeutic analgesic for acute and chronic neuropathic pain as an alternative to morphine. Oxycodone emerged as a drug with widespread abuse. This article brings together an integrated, detailed review of the pharmacology of oxycodone, preclinical and clinical studies of pain and abuse, and recent advances to identify potential opioid analgesics without abuse liability.

Role of sex hormones in the effects of sleep deprivation on methamphetamine reward memory

Sleep deficiency is known as an important risk factor for relapse to drug abuse, especially for the powerful psychostimulant methamphetamine (METH). On the other hand, both drug addiction and sleep neurobiology are affected by sex hormones. We, therefore, aimed to examine the probable effects of sleep deprivation (SD) on methamphetamine (METH) reward memory in male and female rats. Moreover, we asked if sex hormones influence the effects of SD on METH reward memory. Adult male and female Wistar rats were divided into two main groups, sham and gonadectomized groups. Three weeks later, they were conditioned to receive METH (2 mg/kg, i.p.) in the conditioned place preference. METH reward memory was then reinstated following a 10-day extinction period. SD was induced for 72 h, either before or after extinction, in different groups. In gonadectomized animals, they daily received either subcutaneous administration of estrogen (5 μg/0.1 ml oil) or progesterone (2 mg/0.1 ml oil) or dihydrotestosterone (25 mg/0.1 ml oil) for thirteen days, from post-conditioning day to reinstatement session. We found that SD facilitated relapse to METH reward memory, depending on the time interval between SD and METH reinstatement. Furthermore, we found that estrogen and SD showed synergistic effects to facilitate METH reward memory, whereas testosterone and progesterone revealed inhibitory effects in the controls, but not in the SD, animals. Our findings would seem to suggest that sex hormones should be considered as determinant factors to manage METH abuse and relapse to METH seeking/taking behavior, especially for those with sleep deficiency.

Matrix metalloproteinase activity during methamphetamine cued relapse

Relapse to drug seeking involves transient synaptic remodelling that occurs in response to drug-associated cues. This remodelling includes activation of matrix metalloproteinases (MMPs) to initiate catalytic signalling in the extracellular matrix in the nucleus accumbens core (NAcore). We hypothesized that MMP activity would be increased in the NAcore during cue-induced methamphetamine (meth) seeking in a rat model of meth use and relapse. Male and female rats had indwelling jugular catheters and bilateral intracranial cannula targeting the NAcore surgically implanted. Following recovery, rats underwent meth or saline self-administration (6 h/day for 15 days) in which active lever responding was paired with a light + tone stimulus complex, followed by home cage abstinence. Testing occurred after 7 or 30 days of abstinence. On test day, rats were microinjected with a fluorescein isothiocyanate (FITC)-quenched gelatin substrate that fluoresces following cleavage by MMP-2,9, allowing for the quantification of gelatinase activity during cued-relapse testing. MMP-2,9 activity was significantly increased in the NAcore by meth cues presentation after 7 and 30 days of abstinence, indicating that remodelling by MMPs occurs during presentation of meth associated cues. Surprisingly, although cue-induced seeking increased between Days 7 and 30, MMP-2,9 activity did not increase. These findings indicate that although MMP activation is elicited during meth cue-induced seeking, MMP activation did not parallel the meth seeking that occurs during extended drug abstinence.

Sex/Gender Differences in the Time-Course for the Development of Substance Use Disorder: A Focus on the Telescoping Effect

Sex/gender effects have been demonstrated for multiple aspects of addiction, with one of the most commonly cited examples being the "telescoping effect" where women meet criteria and/or seek treatment of substance use disorder (SUD) after fewer years of drug use as compared with men. This phenomenon has been reported for multiple drug classes including opioids, psychostimulants, alcohol, and cannabis, as well as nonpharmacological addictions, such as gambling. However, there are some inconsistent reports that show either no difference between men and women or opposite effects and a faster course to addiction in men than women. Thus, the goals of this review are to evaluate evidence for and against the telescoping effect in women and to determine the conditions/populations for which the telescoping effect is most relevant. We also discuss evidence from preclinical studies, which strongly support the validity of the telescoping effect and show that female animals develop addiction-like features (e.g., compulsive drug use, an enhanced motivation for the drug, and enhanced drug-craving/vulnerability to relapse) more readily than male animals. We also discuss biologic factors that may contribute to the telescoping effect, such as ovarian hormones, and its neurobiological basis focusing on the mesolimbic dopamine reward pathway and the corticomesolimbic glutamatergic pathway considering the critical roles these pathways play in the rewarding/reinforcing effects of addictive drugs and SUD. We conclude with future research directions, including intervention strategies to prevent the development of SUD in women. SIGNIFICANCE STATEMENT: One of the most widely cited gender/sex differences in substance use disorder (SUD) is the "telescoping effect," which reflects an accelerated course in women versus men for the development and/or seeking treatment for SUD. This review evaluates evidence for and against a telescoping effect drawing upon data from both clinical and preclinical studies. We also discuss the contribution of biological factors and underlying neurobiological mechanisms and highlight potential targets to prevent the development of SUD in women.

Global brain c-Fos profiling reveals major functional brain networks rearrangements after alcohol reexposure

Many fundamental questions on alcohol use disorder (AUD) are frequently difficult to address by examining a single brain structure, but should be viewed from the whole brain perspective. c-Fos is a marker of neuronal activation. Global brain c-Fos profiling in rodents represents a promising platform to study brain functional networks rearrangements in AUD. We used a mouse model of alcohol drinking in IntelliCage. We trained mice to voluntarily drink alcohol, next subjected them to withdrawal and alcohol reexposure. We have developed a dedicated image computational workflow to identify c-Fos-positive cells in three-dimensional images obtained after whole-brain optical clearing and imaging in the light-sheet microscope. We provide a complete list of 169 brain structures with annotated c-Fos expression. We analyzed functional networks, brain modularity and engram index. Brain c-Fos levels in animals reexposed to alcohol were different from both control and binge drinking animals. Structures involved in reward processing, decision making and characteristic for addictive behaviors, such as precommissural nucleus, nucleus Raphe, parts of colliculus and tecta stood out particularly. Alcohol reexposure leads to a massive change of brain modularity including a formation of numerous smaller functional modules grouping structures involved in addiction development. Binge drinking can lead to substantial functional remodeling in the brain. We provide a list of structures that can be used as a target in pharmacotherapy but also point to the networks and modules that can hold therapeutic potential demonstrated by a clinical trial in patients.

Feasibility of Remotely Assessing Hormonal Contraceptive Use and Smoking-Related Symptomatology: Evidence from a Preliminary Prospective Cohort Study

Background

Half of women who smoke cigarettes also use hormonal contraceptives (HCs). Prior research suggests that variations in ovarian hormones may undermine smoking cessation efforts made by premenopausal women. However, clinical findings of these hormonal effects are inconsistent, potentially due to methodological limitations. The goal of this preliminary prospective cohort study is to determine the feasibility and acceptability of a fully remote protocol to longitudinally examine changes in smoking-related behavior and symptoms in relation to hormone use in women of reproductive age.

Methods

Eligible participants (n = 60) were biologically female, current age 18-35 years old, smokes ≥ 5 cigarettes/day, and classified into three groups: naturally-cycling (NC; n = 17), using a monophasic oral contraceptive (OC; n = 21), or using depot medroxyprogesterone acetate (DMPA; n = 22). Participants completed daily surveys and weekly dried blood spot collections.

Results

Overall, 92% (55/60) participants completed the study with 90% of daily surveys completed and 87% of participants collecting at least 5 of the 6 dried blood spot samples. Participants were "somewhat" (13%) or "extremely" (87%) likely to participate in the study again. Preliminary observations also suggested differences in self-reported cigarettes/day and premenstrual pain over time by study group.

Conclusions

This study outlines a fully remote protocol that may be used to clarify the relationships between hormonal contraceptive use and smoking-related outcomes over time. Preliminary results add to existing evidence that HC use may reduce relapse risk for premenopausal women.

Net gain and loss: influence of natural rewards and drugs of abuse on perineuronal nets

Overindulgence, excessive consumption, and a pattern of compulsive use of natural rewards, such as certain foods or drugs of abuse, may result in the development of obesity or substance use disorder, respectively. Natural rewards and drugs of abuse can trigger similar changes in the neurobiological substrates that drive food- and drug-seeking behaviors. This review examines the impact natural rewards and drugs of abuse have on perineuronal nets (PNNs). PNNs are specialized extracellular matrix structures that ensheathe certain neurons during development over the critical period to provide synaptic stabilization and a protective microenvironment for the cells they surround. This review also analyzes how natural rewards and drugs of abuse impact the density and maturation of PNNs within reward-associated circuitry of the brain, which may contribute to maladaptive food- and drug-seeking behaviors. Finally, we evaluate the relatively few studies that have degraded PNNs to perturb reward-seeking behaviors. Taken together, this review sheds light on the complex way PNNs are regulated by natural rewards and drugs and highlights a need for future studies to delineate the molecular mechanisms that underlie the modification and maintenance of PNNs following exposure to rewarding stimuli.

Involvement of GABAA receptors of lateral habenula in the acquisition and expression phases of morphine-induced place preference in male rats

The lateral habenula (LHb) is a critical brain structure involved in the aversive response to drug abuse. It has been determined that the gamma-aminobutyric acid (GABA)-ergic system plays the main role in morphine dependency. The role of GABA type A receptors (GABAARs) in LHb on morphine-induced conditioned place preference (CPP) remains unknown. In this study, the effect of bilateral intra-LHb microinjection of GABAAR agonist and antagonist on the acquisition and expression phases of CPP, utilizing a 5-day CPP paradigm in male rats, was evaluated. Subcutaneous administration of different doses of morphine caused a dose-dependent CPP. Intra-LHb microinjection of the GABAAR agonist, muscimol, in combination with morphine (5 mg/kg; subcutaneously) enhanced CPP scores in the acquisition phase of morphine CPP, whereas the GABAAR antagonist, bicuculline, significantly reduced the conditioning scores in the acquisition phase. Furthermore, pretreatment with a high dose of bicuculline reversed the additive effect of muscimol during the acquisition phase, yet the low dose of antagonist had no significant effect on agonist-induced CPP scores. On the other hand, muscimol (3 µg/rat) significantly increased CPP scores in the expression phase but bicuculline did not induce a significant effect on CPP scores. Bicuculline and muscimol microinjections did not affect locomotor activity in the testing sessions. Our results confirm that GABAARs in LHb play an active role in morphine reward. In addition, microinjections of bicuculline/muscimol may alter the morphine response through the GABAergic system.

Nicotinic receptors promote susceptibility to social stress in female mice linked with neuroadaptations within VTA dopamine neurons

There are about twice as many women as men who experience depression during their lifetime. Although life circumstances and especially exposure to stressful situations constitute a major risk factor to develop depression, the underlying mechanisms have yet to be unraveled. We employed the chronic social defeat procedure to elicit depressive-like symptoms in females and ketamine to validate the model. We performed ex-vivo patch clamp recordings to assess cellular adaptations and used pharmacological agents to dissect these deregulations. Chronic social defeat exposure triggers a hyperactivity of VTA putative dopamine (DA) neurons in females susceptible to stress but not resilient ones. This hyperactivity was fully reversed by a single administration of ketamine. In virally-identified brain circuits of both susceptible and resilient females, we found a hypercholinergic tone to the VTA arising from the laterodorsal tegmentum. Application of puffs of nicotine revealed a decreased sensitivity of DA neurons in resilient mice when compared to naive or susceptible ones. The in vivo acute administration of the positive allosteric modulator for α7 nicotinic acetylcholine receptors (nAChRs) not only increased susceptibility to stress by enhancing activity of VTA DA neurons, but also triggered a switch in phenotype from resilient to susceptible. Our data unravel dysregulations of VTA DA neurons activity exclusively in females exhibiting depressive-like symptoms and identify VTA nAChRs as key molecular substrates that exacerbate susceptibility to stress.

Estrogen receptors observed at extranuclear neuronal sites and in glia in the nucleus accumbens core and shell of the female rat: Evidence for localization to catecholaminergic and GABAergic neurons

Estrogens affect dopamine-dependent diseases/behavior and have rapid effects on dopamine release and receptor availability in the nucleus accumbens (NAc). Low levels of nuclear estrogen receptor (ER) α and ERβ are seen in the NAc, which cannot account for the rapid effects of estrogens in this region. G-protein coupled ER 1 (GPER1) is observed at low levels in the NAc shell, which also likely does not account for the array of estrogens' effects in this region. Prior studies demonstrated membrane-associated ERs in the dorsal striatum; these experiments extend those findings to the NAc core and shell. Single- and dual-immunolabeling electron microscopy determined whether ERα, ERβ, and GPER1 are at extranuclear sites in the NAc core and shell and whether ERα and GPER1 were localized to catecholaminergic or γ-aminobutyric acid-ergic (GABAergic) neurons. All three ERs are observed, almost exclusively, at extranuclear sites in the NAc, and similarly distributed in the core and shell. ERα, ERβ, and GPER1 are primarily in axons and axon terminals suggesting that estrogens affect transmission in the NAc via presynaptic mechanisms. About 10% of these receptors are found on glia. A small proportion of ERα and GPER1 are localized to catecholaminergic terminals, suggesting that binding at these ERs alters release of catecholamines, including dopamine. A larger proportion of ERα and GPER1 are localized to GABAergic dendrites and terminals, suggesting that estrogens alter GABAergic transmission to indirectly affect dopamine transmission in the NAc. Thus, the localization of ERs could account for the rapid effects of estrogen in the NAc.

Sex- and Dose-Dependent Differences in the Development of an Addiction-Like Phenotype Following Extended-Access Fentanyl Self-Administration

Opioid use disorder (OUD) is a major epidemic in the United States, and fentanyl is a major culprit. The National Institute on Drug Abuse has highlighted an urgent need for research on the risks and outcomes of OUD with fentanyl; a better understanding of sex/gender differences is also critically needed given that the opioid epidemic has been particularly impactful on women. In response to this need, we developed a rat model of OUD with fentanyl and showed that sex impacts relapse vulnerability following extended-access self-administration under a low fentanyl dose. Here, our goal was to determine sex differences across a broad dose range, including high doses expected to maximize the expression of addiction-like features (e.g., vulnerability to relapse and physical dependence). Male and female rats were assigned to self-administer one of four fentanyl doses (0.25, 0.75, 1.5, and 3.0 µg/kg/infusion), and once they acquired, they were given extended (24-h/day), intermittent access (2, 5 min trials/h, fixed-ratio 1) to fentanyl for 10 days. Physical dependence (spontaneous weight loss) was assessed during early withdrawal, and relapse vulnerability was assessed on withdrawal day 15 using an extinction/cue-induced reinstatement procedure. Despite markedly higher intake in the high- versus low-dose groups, each group responded similarly during relapse testing (extinction and cue-induced reinstatement). However, number of infusions, or frequency of use, during extended access was predictive of later vulnerability to relapse, whereas total intake impacted physical dependence given that weight loss only occurred following the discontinuation of fentanyl self-administration at the three highest doses. Females self-administered more fentanyl each day and within each binge (active trial), and had longer lasting weight loss during withdrawal than males. Relapse vulnerability was also higher in females than males and highest in females tested during estrus. These findings indicate that sex is an important risk factor for patterns and levels of fentanyl intake, relapse, and physical dependence, and while fentanyl intake predicts physical dependence, frequency of use predicts relapse.

FACTORS CONTRIBUTING TO THE ESCALATION OF ALCOHOL CONSUMPTION

Understanding factors that contribute to the escalation of alcohol consumption is key to understanding how an individual transitions from non/social drinking to AUD and to providing better treatment. In this review, we discuss how the way ethanol is consumed as well as individual and environmental factors contribute to the escalation of ethanol consumption from intermittent low levels to consistently high levels. Moreover, we discuss how these factors are modelled in animals. It is clear a vast array of complex, interacting factors influence changes in alcohol consumption. Some of these factors act early in the acquisition of ethanol consumption and initial escalation, while others contribute to escalation of ethanol consumption at a later stage and are involved in the development of alcohol dependence. There is considerable need for more studies examining escalation associated with the formation of dependence and other hallmark features of AUD, especially studies examining mechanisms, as it is of considerable relevance to understanding and treating AUD.

Sex-dependent Effects of the Drugs of Abuse Amphetamine and the Smart Drug 3,4-Methylenedioxypyrovalerone on Fear Memory Generalization in Rats

In recent years there has been an increase in the development of new synthetic drugs, among which the "bath salt" 3,4-methylenedioxypyrovalerone (MDPV), a psychostimulant with a mechanism of action similar to those of cocaine and amphetamine, stands out. Drugs of abuse have been consistently shown to affect memory function in male rodents. We have recently shown that amphetamine and MDPV induce generalization of fear memory in an inhibitory avoidance discrimination task in male rats. Although abuse of illicit drugs is more prevalent in men than in women, several studies have demonstrated that females are more vulnerable to the effects of drugs of abuse than males and the effects caused by substance dependence on memory in females are still under-investigated. Thus, we examined the effects of subchronic amphetamine or MDPV administrations on memory in a contextual fear conditioning/generalization paradigm in adult male and female rats. Animals were given daily subchronic injections of the drugs, starting 6 days prior the beginning of the behavioral procedures until the end of the paradigm. On day 1 of the experimental protocol, all rats were exposed to a safe context and, the day after, to a slightly different chamber where they received an unsignaled footshock. Twenty-four and forty-eight hours later, freezing behavior and emission of 22 kHz-ultrasonic vocalizations (USVs) were measured in the two different contexts to assess fear memory retention and generalization. Our results indicate that MDPV treatment altered freezing in both sexes, USVs were affected by amphetamine in males while by MDPV in females.

The Buprenorphine Analogue BU10119 Attenuates Drug-Primed and Stress-Induced Cocaine Reinstatement in Mice

There are no Food and Drug Administration-approved medications for cocaine use disorder, including relapse. The μ-opioid receptor (MOPr) partial agonist buprenorphine alone or in combination with naltrexone has been shown to reduce cocaine-positive urine tests and cocaine seeking in rodents. However, there are concerns over the abuse liability of buprenorphine. Buprenorphine's partial agonist and antagonist activity at the nociception receptor (NOPr) and κ-opioid receptor (KOPr), respectively, may contribute to its ability to inhibit cocaine seeking. Thus, we hypothesized that a buprenorphine derivative that exhibits antagonist activity at MOPr and KOPr with enhanced agonist activity at the NOPr could provide a more effective treatment. Here we compare the pharmacology of buprenorphine and two analogs, BU10119 and BU12004, in assays for antinociception and for cocaine- and stress-primed reinstatement in the conditioned place preference paradigm. In vitro and in vivo assays showed that BU10119 acts as an antagonist at MOPr, KOPr, and δ-opioid receptor (DOPr) and a partial agonist at NOPr, whereas BU12004 showed MOPr partial agonist activity and DOPr, KOPr, and NOPr antagonism. BU10119 and buprenorphine but not BU12004 lessened cocaine-primed reinstatement. In contrast, BU10119, BU12004, and buprenorphine blocked stress-primed reinstatement. The selective NOPr agonist SCH221510 but not naloxone decreased cocaine-primed reinstatement. Together, these findings are consistent with the concept that NOPr agonism contributes to the ability of BU10119 and buprenorphine to attenuate reinstatement of cocaine-conditioned place preference in mice. The findings support the development of buprenorphine analogs lacking MOPr agonism with increased NOPr agonism for relapse prevention to cocaine addiction. SIGNIFICANCE STATEMENT: There are no Food and Drug Administration-approved medications for cocaine use disorder. Buprenorphine has shown promise as a treatment for cocaine relapse prevention; however, there are concerns over the abuse liability of buprenorphine. Here we show a buprenorphine analogue, BU10119, which lacks μ-opioid receptor agonism and inhibits cocaine-primed and stress-primed reinstatement in a conditioned place-preference paradigm. The results suggest the development of BU10119 for the management of relapse to cocaine seeking.

Sex-specific role for prefrontal cortical protein interacting with C kinase 1 in cue-induced cocaine seeking

Disruption of prefrontal glutamate receptor interacting protein (GRIP), which anchors GluA2-containing AMPA receptors (AMPARs) into the synaptic membrane, potentiates cue-induced cocaine seeking in both males and females. Protein interacting with C kinase 1 (PICK1) plays an opposing role to that of GRIP, removing AMPARs from the synapse. Consistent with our hypothesis that disruption of PICK1 in the mPFC would lead to a decrease in addiction-like behaviour, we found that conditional deletion of PICK1 in the mPFC attenuates cue-induced cocaine seeking in male mice. However, prefrontal PICK1 deletion had the opposite effect in females, leading to an increase in cue-induced reinstatement of cocaine seeking. We did not see any effects of PICK1 knockdown on sucrose taking or seeking, suggesting the sex-specific effects do not generalise to natural reinforcers. These findings suggest the role of PICK1 in the prefrontal cortex of females may not be consistent with its accepted role in males. To determine whether these sex differences were influenced by gonadal hormones, we gonadectomised a cohort of males and found that removal of circulating androgens eliminated the effect of prefrontal PICK1 knockdown. As there was no effect of gonadectomy on its own on any of the behavioural measures collected, our results suggest that androgens may be involved in compensatory downstream effects of PICK1 knockdown. Taken together, these results highlight the need for consideration of sex as a biological variable when examining mechanisms underlying all behaviours, as convergent sex differences can reveal different mechanisms where behavioural sex differences do not exist.

Addiction among women and sexual minority groups

Gender-related alcohol and drug abuse problems are related not only to biologic differences but also to social and environment factors, all of which can influence the clinical presentation, consequences of use, and treatment approaches. The number of women becoming addicted to alcohol or drugs of abuse has significantly increased with women becoming the fastest-growing group of substance abusers in the United States. Given that women experience a more rapid progression of their addiction than men, it is important that we understand and address the differences to help develop prevention and treatment programs that are tailored for women, incorporating trauma assessment and management, comorbidities, financial independence, pregnancy, and child care.

Animal Models of Drug Relapse and Craving after Voluntary Abstinence: A Review

Relapse to drug use during abstinence is a defining feature of addiction. During the last several decades, this clinical scenario has been studied at the preclinical level using classic relapse/reinstatement models in which drug seeking is assessed after experimenter-imposed home-cage forced abstinence or extinction of the drug-reinforced responding in the self-administration chambers. To date, however, results from studies using rat relapse/reinstatement models have yet to result in Food and Drug Administration-approved medications for relapse prevention. The reasons for this state of affairs are complex and multifaceted, but one potential reason is that, in humans, abstinence is often self-imposed or voluntary and occurs either because the negative consequences of drug use outweigh the drug's rewarding effects or because of the availability of nondrug alternative rewards that are chosen over the drug. Based on these considerations, we and others have recently developed rat models of relapse after voluntary abstinence, achieved either by introducing adverse consequences to drug taking (punishment) or seeking (electric barrier) or by providing mutually exclusive choices between the self-administered drug and nondrug rewards (palatable food or social interaction). In this review, we provide an overview of these translationally relevant relapse models and discuss recent neuropharmacological findings from studies using these models. We also discuss sex as a biological variable, future directions, and clinical implications of results from relapse studies using voluntary abstinence models. Our main conclusion is that the neuropharmacological mechanisms controlling relapse to drug seeking after voluntary abstinence are often different from the mechanisms controlling relapse after home-cage forced abstinence or reinstatement after extinction. SIGNIFICANCE STATEMENT: This review describes recently developed rat models of relapse after voluntary abstinence, achieved either by introducing adverse consequences to drug taking or seeking or by providing mutually exclusive choices between the self-administered drug and nondrug rewards. This review discusses recent neuropharmacological findings from studies using these models and discusses future directions and clinical implications.

S-Equol mitigates motivational deficits and dysregulation associated with HIV-1

Motivational deficits (e.g., apathy) and dysregulation (e.g., addiction) in HIV-1 seropositive individuals, despite treatment with combination antiretroviral therapy, necessitates the development of innovative adjunctive therapeutics. S-Equol (SE), a selective estrogen receptor β agonist, has been implicated as a neuroprotective and/or neurorestorative therapeutic for HIV-1 associated neurocognitive disorders (HAND); its therapeutic utility for motivational alterations, however, has yet to be systematically evaluated. Thus, HIV-1 transgenic (Tg) and control animals were treated with either a daily oral dose of SE (0.2 mg) or vehicle and assessed in a series of tasks to evaluate goal-directed and drug-seeking behavior. First, at the genotypic level, motivational deficits in HIV-1 Tg rats treated with vehicle were characterized by a diminished reinforcing efficacy of, and sensitivity to, sucrose. Motivational dysregulation was evidenced by enhanced drug-seeking for cocaine relative to control animals treated with vehicle. Second, treatment with SE ameliorated both motivational deficits and dysregulation in HIV-1 Tg rats. Following a history of cocaine self-administration, HIV-1 Tg animals treated with vehicle exhibited lower levels of dendritic branching and a shift towards longer dendritic spines with decreased head diameter. Treatment with SE, however, led to long-term enhancements in dendritic spine morphology in HIV-1 Tg animals supporting a potential underlying basis by which SE exerts its therapeutic effects. Taken together, SE restored motivated behavior in the HIV-1 Tg rat, expanding the potential clinical utility of SE to include both neurocognitive and affective alterations.

Activation of G-protein coupled estradiol receptor 1 in the dorsolateral striatum attenuates preference for cocaine and saccharin in male but not female rats

There are sex differences in the response to psychomotor stimulants, where females exhibit a greater response than males, due to the presence of the gonadal hormone estradiol (E2). Extensive research has shown that E2 enhances drug-seeking and the rewarding properties of cocaine for females. The role of E2 in male drug-seeking, however, is not well understood. The current study investigated pharmacological manipulation of E2 receptors in the dorsolateral striatum (DLS) on preference for cocaine in gonad-intact male and female rats. In males, activation of G-protein coupled E2 receptor 1 (GPER1), via administration of ICI 182,780 or G1, attenuated conditioned place preference for 10 mg/kg cocaine, while inhibition of GPER1, via G15, enhanced preference at a 5 mg/kg cocaine dose. Similarly, GPER1 activation, via G1, prevented males from forming a preference for 0.1% saccharin (SACC) versus plain water. Surprisingly, activation of GPER1 did not alter preference for cocaine or SACC in females. These studies also examined the quantity of E2 receptor mRNA in the dorsal striatum, using qPCR. No sex differences in relative mRNA expression of ERα, ERβ, and GPER1 were observed. However, there was greater GPER1 mRNA, relative to ERα and ERβ, in both males and females. The results presented here indicate that E2, acting via GPER1, may be protective against drug preference in male rats.

Regulation of risky decision making by gonadal hormones in males and females

Psychiatric diseases characterized by dysregulated risky decision making are differentially represented in males and females. The factors that govern such sex differences, however, remain poorly understood. Using a task in which rats make discrete trial choices between a small, "safe" food reward and a large food reward accompanied by varying probabilities of footshock punishment, we recently showed that females are more risk averse than males. The objective of the current experiments was to test the extent to which these sex differences in risky decision making are mediated by gonadal hormones. Male and female rats were trained in the risky decision-making task, followed by ovariectomy (OVX), orchiectomy (ORX), or sham surgery. Rats were then retested in the task, under both baseline conditions and following administration of estradiol and/or testosterone. OVX increased choice of the large, risky reward (increased risky choice), an effect that was attenuated by estradiol administration. In contrast, ORX decreased risky choice, but testosterone administration was without effect in either ORX or sham males. Estradiol, however, decreased risky choice in both groups of males. Importantly, none of the effects of hormonal manipulation on risky choice were due to altered shock sensitivity or food motivation. These data show that gonadal hormones are required for maintaining sex-typical profiles of risk-taking behavior in both males and females, and that estradiol is sufficient to promote risk aversion in both sexes. The findings provide novel information about the mechanisms supporting sex differences in risk taking and may prove useful in understanding sex differences in the prevalence of psychiatric diseases associated with altered risk taking.

Effects of early life stress on cocaine intake in male and female rhesus macaques

RATIONALE

It is critical to identify potential risk factors, such as a history of early life stress (ELS), that may confer specific vulnerabilities to increased drug intake.

OBJECTIVE

In this study, we examined whether male and female rhesus monkeys with a history of ELS (infant maltreatment; MALT) demonstrated significantly greater cocaine intake compared with controls.

METHODS

Monkeys were trained to self-administer cocaine during 4-h sessions at a peak dose (0.003-0.1 mg/kg/infusion; extended access, "EA peak") and a dose of 0.1 mg/kg/infusion (EA 0.1) of cocaine. These data were compared with data obtained previously in monkeys trained during 1-h limited access (LA) sessions at the same peak dose of cocaine used here (Wakeford et al. Psychopharmacology, 236:2785-2796, 2019).

RESULTS

Monkeys significantly increased total number of infusions earned in EA compared with LA, but total session response rates significantly decreased in EA compared with LA. There was no evidence of escalation in drug intake when we compared response rates to obtain the first 20 cocaine infusions between LA and EA peak conditions. Moreover, there was no evidence of escalation in drug intake during an additional 7 weeks of self-administration at 0.1 mg/kg/injection.

CONCLUSIONS

The current study expands on previous reports demonstrating that rhesus macaques did not escalate cocaine intake under the experimental conditions employed and extended these findings by using a unique population of nonhuman primates with a history of infant MALT to test the hypothesis that ELS is a risk factor for escalation of cocaine intake in nonhuman primates. There was no clear evidence of escalation in cocaine intake as a consequence of ELS.

Sex differences in pregabalin-seeking like behavior in a conditioned place preference paradigm

Substance abuse is a chronic, relapsing disorder characterized by compulsive drug use regardless of negative consequences. Incremental increases in pregabalin abuse have been observed in Saudi Arabia and throughout the world. In previous studies, the potential for pregabalin abuse with escalating doses of the drug (30, 60, 90, and 120 mg/kg) were investigated in male mice. Notably, researchers have argued that women may exhibit a greater tendency to consume drugs without a prescription to alleviate stress and depression. Moreover, female subjects are more prone to impulsivity in drug intake or abuse than their male counterparts. Therefore, in the present study, we compared the potential for pregabalin abuse between male and female mice using a conditioned place preference paradigm. Male and female BALB/c mice were divided into four groups based on the pregabalin dose administered (30, 60, 90, or 120 mg/kg, intraperitoneal). Preference scores were then calculated and compared between male and female mice in each dosage group. Interestingly, preference scores were significantly higher in female mice than in male mice at dosages of 30 and 120 mg/kg. These findings indicate that female mice may be more prone to pregabalin abuse and tolerance than male mice. These results might be helpful to the healthcare providers and policymakers to consider these sex differences in choosing therapeutic plans and consider alternatives to the misused prescription medications.

Sex and strain differences in dynamic and static properties of the mesolimbic dopamine system

Sex is a biological variable that contributes to the incidence, clinical course, and treatment outcome of brain disorders. Chief among these are disorders associated with the dopamine system. These include Parkinson's disease, ADHD, schizophrenia, and mood disorders, which show stark differences in prevalence and outcome between men and women. In order to reveal the influence of biological sex as a risk factor in these disorders, there is a critical need to collect fundamental information about basic properties of the dopamine system in males and females. In Long Evans rats, we measured dynamic and static properties related to the mesolimbic dopamine system. Static measures included assessing ventral tegmental area (VTA) dopamine cell number and volume and expression of tyrosine hydroxylase and dopamine transporter. Dynamic measures in behaving animals included assessing (1) VTA neuronal encoding during learning of a cue-action-reward instrumental task and (2) dopamine release in the nucleus accumbens in response to electrical stimulation of the VTA, vesicular depletion of dopamine, and amphetamine. We found little or no sex difference in these measures, suggesting sexual congruency in fundamental static and dynamic properties of dopamine neurons. Thus, dopamine related sex-differences are likely mediated by secondary mechanisms that flexibly influence the function of the dopamine cells and circuits. Finally, we noted that most behavioral sex differences had been reported in Sprague-Dawley rats and repeated some of the above measures in that strain. We found some sex differences in those animals highlighting the importance of considering strain differences in experimental design and result interpretation.

Administration of Exogenous Hormones and the Implications for Cigarette Smoking-Related Behaviors

PURPOSE OF REVIEW

Preclinical evidence indicates progesterone and estrogen influence drug-taking behaviors, including nicotine/tobacco. However, clinical research on this relationship is less clear. This lack of clarity may be due to measuring naturally occurring endogenous hormones to examine this relationship, which introduces substantial error. Therefore, the goal of this review is to examine the link between the delivery of exogenous hormones and cigarette smoking-related behavior.

RECENT FINDINGS

Exogenous progesterone may have favorable effects on cognition, symptomatology, consumption, and smoking cessation. Hormonal replacement therapy does not have a clear relationship with smoking-related behaviors. Oral contraceptive use may have adverse effects on stress response, nicotine metabolism, and symptomatology. Additional research is needed to explore how the administration of exogenous hormones may (a) strengthen research methodology on this topic, (b) enhance our understanding of the role of progesterone/estrogen on smoking-related behaviors, and (c) improve smoking cessation outcomes.

Effect of short-term intake of high- and low-concentrations of sucrose solution on the neurochemistry of male and female mice

The effect of short-term intake of high- and low-concentrations of sucrose solution on the neurochemistry of male and female mice was studied. The body weight, feed intake, sucrose solution consumption and brain monoamine neurotransmitters were determined after 34 days' intake of 1% and 8% sucrose solutions. The gene expression and protein levels related to dopamine and opioids were also determined. The results showed that the intake of 1% and 8% sucrose solution for 34 days did not cause significant changes in the weight development of both male and female mice. The preference for sucrose varies with sex. Both males and females had greater preference for the high concentration sucrose solution than the low concentration sucrose solution. The continuous intake of sucrose stimulated the release of monoamine neurotransmitters (DA, 5-HT, NE) in the brains of mice, and the reward effect of 8% sucrose solution is significantly higher than that of 1% sucrose solution. The sex of mice did not affect the release of neurotransmitters. The gene expressions of D1 and D2 were up-regulated in the 1% sucrose group of male mice, while the OPRM1 gene expression was down-regulated. The expression of these three genes in the 8% sucrose group of male mice was all down-regulated, while the gene expressions of D1 and D2 in the 1% and 8% sucrose group (p < 0.05) of female mice were both up-regulated.

Swimming exercise during morphine abstinence in parents-to-be attenuated morphine-induced conditioned place preference and locomotor sensitization only in male rat offspring

This study was designed to examine the effects of swimming exercise during morphine abstinence in parents-to-be before mating on morphine-induced conditioned place preference (CPP) and locomotor sensitization in the pubertal male and female rat offspring. Male and female Wistar rats were injected with bi-daily doses (10 mg/kg, 12 h intervals) of morphine for 14 days. The exercising rats exposed to a regular swimming exercise (45 min/d, five days per a week) during 30 days of morphine abstinence before mating. Then, the pubertal male and female rat offspring were tested for morphine-induced CPP and locomotor sensitization (using the open field). The results showed that the pubertal male offspring of the morphine-abstinent parents-to-be exhibited an increase in CPP to morphine and locomotor activity after morphine challenge than the offspring from the control group. While, swimming exercise in morphine-abstinent parents-to-be decreased CPP score and locomotor activity in the pubertal male offspring than control offspring. Thus, exposure to swimming exercise in morphine-abstinent parents-to-be before mating may exert a protective effect against morphine-induced reward and locomotor sensitization in their pubertal offspring which may prevent the vulnerability of the first generation to drug abuse following opiate-addicted parents before mating.

The role of catecholamines in modulating responses to stress: Sex-specific patterns, implications, and therapeutic potential for post-traumatic stress disorder and opiate withdrawal

Emotional arousal is one of several factors that determine the strength of a memory and how efficiently it may be retrieved. The systems at play are multifaceted; on one hand, the dopaminergic mesocorticolimbic system evaluates the rewarding or reinforcing potential of a stimulus, while on the other, the noradrenergic stress response system evaluates the risk of threat, commanding attention, and engaging emotional and physical behavioral responses. Sex-specific patterns in the anatomy and function of the arousal system suggest that sexually divergent therapeutic approaches may be advantageous for neurological disorders involving arousal, learning, and memory. From the lens of the triple network model of psychopathology, we argue that post-traumatic stress disorder and opiate substance use disorder arise from maladaptive learning responses that are perpetuated by hyperarousal of the salience network. We present evidence that catecholamine-modulated learning and stress-responsive circuitry exerts substantial influence over the salience network and its dysfunction in stress-related psychiatric disorders, and between the sexes. We discuss the therapeutic potential of targeting the endogenous cannabinoid system; a ubiquitous neuromodulator that influences learning, memory, and responsivity to stress by influencing catecholamine, excitatory, and inhibitory synaptic transmission. Relevant preclinical data in male and female rodents are integrated with clinical data in men and women in an effort to understand how ideal treatment modalities between the sexes may be different.

Influences of the Menstrual Phase on Cortisol Response to Stress in Nicotine Dependent Women: A Preliminary Examination

INTRODUCTION

Evidence indicates that menstrual cycle phase plays a role in smoking withdrawal symptoms and craving. Stress increases these symptoms. Whether the stress regulatory mechanism is associated with menstrual phase and withdrawal symptoms is not well understood.

METHODS

Thirty-seven female smokers and 16 female nonsmokers were asked to complete a laboratory session. In each group, approximately half of the participants were tested when they were in the follicular phase and the other half was tested in the luteal phase. The session included resting baseline, stress, and recovery periods. Saliva samples for the measurement of cortisol and subjective measures of craving and withdrawal symptoms were collected at the end of each period.

RESULTS

A series of repeated measures analysis of covariance found a significant smoking group × menstrual phase × sampling time interaction in cortisol levels (p < .05). Follow-up analyses indicated a reduced cortisol stress response in the luteal group relative to the follicular group in smokers (p < .02). This difference was not found in nonsmokers.

CONCLUSIONS

Menstrual cycle phase is related to hormonal stress response and smoking withdrawal symptomatology.

IMPLICATIONS

We show influences of the menstrual cycle phase on stress response among smokers. This is demonstrated by a reduced cortisol response to stress in the luteal group relative to the follicular group among smokers. This menstrual phase difference was not found in nonsmokers.

The therapeutic potential of exercise for neuropsychiatric diseases: A review

Exercise is known to have a myriad of health benefits. There is much to be learned from the effects of exercise and its potential for prevention, attenuation and treatment of multiple neuropsychiatric diseases and behavioral disorders. Furthermore, recent data and research on exercise benefits with respect to major health crises, such as, that of opioid and general substance use disorders, make it very important to better understand and review the mechanisms of exercise and how it could be utilized for effective treatments or adjunct treatments for these diseases. In addition, mechanisms, epigenetics and sex differences are examined and discussed in terms of future research implications.

Effect of exogenous progesterone administration on cigarette smoking-related symptomology in oral contraceptive users who smoke

Cigarette smoking-related symptomatology (e.g., craving; SRS) is linked to relapse after a quit attempt. SRS varies by menstrual phase, possibly due to variations in sex hormones (e.g., progesterone), though much of the research to-date has relied on observations from the menstrual cycle acting as a proxy for hormone levels. The goal of this study was to examine the effect of exogenous progesterone on SRS during ad libitum smoking and following overnight abstinence. Oral contraceptive users who smoked completed two 9-day crossover testing periods (7 days of ad libitum smoking and 2 days following overnight abstinence) while taking double-blind active/placebo exogenous progesterone. Participants completed questionnaires to measure SRS. The effect of exogenous progesterone and endogenous hormones (progesterone, estradiol, and progesterone-to-estradiol [P/E₂] ratio) on SRS was assessed with paired t-tests and linear mixed effect models. Participants (n = 53) were, on average, 24 years old and smoked 11 cigarettes per day. During ad libitum smoking, a doubling of the P/E₂ ratio was associated with 0.09 points lower anticipated relief from negative affect (95% confidence interval [CI]: 0.03-0.15 points lower; p = 0.008) and 0.11 points lower psychological reward (95% CI: 0.03-0.18 points lower; p = 0.006). After correction for multiple testing, these associations were not statistically significant: anticipated relief from negative effect (p = 0.10) and psychological reward (p = 0.09). No other significant associations were observed. Although substantial previous literature indicates that progesterone influences SRS, exogenous progesterone administration did not alter SRS here. Additional research is needed to elucidate alternative mechanisms involved in menstrual phase effects on SRS.

Neurochemical and Behavioral Profiling in Male and Female Rats of the Psychedelic Agent 25I-NBOMe

4-Iodo-2,5-dimethoxy-N-(2-methoxybenzyl)phenethylamine (25I-NBOMe), commonly called “N-Bomb,” is a synthetic phenethylamine with psychedelic and entactogenic effects; it was available on the Internet both as a legal alternative to lysergic acid diethylamide (LSD) and as a surrogate of 3,4-methylenedioxy-methamphetamine (MDMA), but now it has been scheduled among controlled substances. 25I-NBOMe acts as full agonist on serotonergic 5-HT2A receptors. Users are often unaware of ingesting fake LSD, and several cases of intoxication and fatalities have been reported. In humans, overdoses of “N-Bomb” can cause tachycardia, hypertension, seizures, and agitation. Preclinical studies have not yet widely investigated the rewarding properties and behavioral effects of this compound in both sexes. Therefore, by in vivo microdialysis, we evaluated the effects of 25I-NBOMe on dopaminergic (DA) and serotonergic (5-HT) transmissions in the nucleus accumbens (NAc) shell and core, and the medial prefrontal cortex (mPFC) of male and female rats. Moreover, we investigated the effect of 25I-NBOMe on sensorimotor modifications as well as body temperature, nociception, and startle/prepulse inhibition (PPI). We showed that administration of 25I-NBOMe affects DA transmission in the NAc shell in both sexes, although showing different patterns; moreover, this compound causes impaired visual responses in both sexes, whereas core temperature is heavily affected in females, and the highest dose tested exerts an analgesic effect prominent in male rats. Indeed, this drug is able to impair the startle amplitude with the same extent in both sexes and inhibits the PPI in male and female rats. Our study fills the gap of knowledge on the behavioral effects of 25I-NBOMe and the risks associated with its ingestion; it focuses the attention on sex differences that might be useful to understand the trend of consumption as well as to recognize and treat intoxication and overdose symptoms.

Subjective response to intranasal nicotine administration in oral contraceptive users and naturally-cycling women

INTRODUCTION

Approximately half of premenopausal women who smoke cigarettes also use hormonal contraceptives, with most using oral contraceptives (OCs). While research on the effects of endogenous hormones on smoking-related outcomes continues to expand, little is known about the influence of OCs on similar outcomes. We sought to explore differences in the subjective response to nicotine by OC use after stratifying by testing condition (e.g., smoking status).

METHODS

Participants were regular (≥5 cigarettes/day) smokers, classified into OC and naturally cycling (NC) groups. All participants completed four total lab sessions by smoking status (ad libitum smoking, acute smoking abstinence) and anticipated progesterone level (low progesterone week (LPW), high progesterone week (HPW)). Each lab session included self-administration of intranasal nicotine (Time 0 min), assessment of subjective response via the Subjective State Scale (-30 and + 5 min).

RESULTS

Compared to the NC group (n = 28), the OC group (n = 14) was younger (26.2 ± 1.1 versus 24.2 ± 1.1; p < 0.001) and had a lower Fagerström Test for Nicotine Dependence score (3.4 ± 0.5 versus 2.6 ± 0.5; p = 0.011). Progesterone-to-estradiol ratios varied significantly by group at three of the four time points (p < 0.05). During ad libitum smoking, the OC group had significantly lower craving after nicotine administration than the NC group (1.93 ± 0.33 versus 2.89 ± 0.23; p = 0.024). No other significant differences in subjective response were identified.

CONCLUSIONS

Despite significantly different hormone levels, group differences in subjective response to nicotine were relatively few. Additional research is needed to elucidate the mechanisms involved in these observations, as well as explore how they may influence cessation in women.

Age- and sex-related changes in the severity of physical and psychological dependence in morphine-dependent rats

Gender- and age-dependent effects on the severity of morphine dependence are still controversial. The aim of this study was to investigate the effects of age and sex on the severity of physical and psychological dependence in morphine-dependent rats. The adult/aged male and female Wistar rats were chronically treated with bi-daily doses (10 mg/kg, at 12 h intervals) of morphine for 14 days. Then, rats were tested for the severity of physical dependence on morphine (spontaneous withdrawal signs), anxiety-like (the elevated plus maze), depressive-like (sucrose preference test) and grooming behaviors after spontaneous morphine withdrawal. We found that the morphine withdrawal signs decreased after 3 and 7 days of withdrawal in female and male rats respectively, while there was no significant difference in overall dependence severity between the two sexes or ages. Also, we found that the withdrawal of morphine led to increased anxiety, depression and obsessive-compulsive behavior in the D (dependent)/Adult male and female rats. Also, the D/aged female and male rats exhibited a reduction in depressive-like behavior than the D/Adult rats. Moreover, the D/female rats exhibited a decreased obsessive-compulsive behavior in both age groups than male rats. We conclude that age has no effect on the duration of withdrawal from morphine and overall dependence severity. While, the duration of withdrawal from morphine was lower in female than male rats. Our results showed a sex difference on the duration of morphine withdrawal and an age difference in the expression of psychological dependence on morphine. Thus, therapeutic strategies may be different for opiate-dependent individuals in physical and psychological dimensions.

Voluntary wheel running effects on intra-accumbens opioid driven diet preferences in male and female rats

Palatability driven feeding and voluntary physical activity are mediated by and influence similar neural mechanisms, notably through the actions of opioids within the nucleus accumbens. Recent studies suggest that access to a voluntary running wheel results in sex dependent behavioral and physiological adaptations related to opioid mediated palatability-driven feeding. To explore this relationship, male and female Wistar rats were given either access to a voluntary running wheel (RUN group) or no access (SED group) for one week prior to being stereotaxically implanted with bilateral cannulae targeting the nucleus accumbens. Following 7 days of recovery, with RUN or SED conditions continuing the duration of the experiment, all rats were assessed daily (2 h/day) for feeding behavior of concurrently accessible high-carbohydrate and high-fat diet for one week. Following this week, all rats were administered the μ-opioid receptor agonist D-Ala2, NMe-Phe4, Glyol5-enkephalin (DAMGO) (0.0025  μg, 0.025  μg, or 0.25 μg/0.5 μl/side) or the opioid antagonist naloxone (20 μg/0.5 μl/side) into the nucleus accumbens and given concurrent access (2 h) to both diets. All groups expressed a significant baseline preference for the high-carbohydrate diet. DAMGO administration, compared to saline treatment, led to significant increased consumption of the high-carbohydrate diet in all treatment groups. While high-fat diet consumption also increased following DAMGO administration, the influence of DAMGO was much more robust for the preferred high-carbohydrate diet in all groups. Compared to males, females consumed significantly more of both diets at baseline and following DAMGO treatment. Both male and female rats in the RUN condition consumed more high-carbohydrate diet compared to rats in the SED condition. While males exhibited similar increased consumption of both diets regardless of RUN or SED condition, females in the RUN condition displayed a greater sensitivity to DAMGO-driven consumption of the preferred high-carbohydrate, compared to SED females.

Women and Addiction: An Update

Gender-related alcohol and drug abuse problems are related not only to biological differences, but also to social and environmental factors, which can influence the clinical presentation, consequences of use, and treatment approaches. Women are becoming the fastest-growing population of substance abusers in the United States. Given that women experience a more rapid progression of their addiction than men, it is important that we understand and address the differences to help develop prevention and treatment programs that are tailored for women, incorporating trauma assessment and management, identification and intervention for medical and psychiatric comorbidities, financial independence, pregnancy, and child care.

Sex differences in the intensity of cross-sensitization between methylphenidate and amphetamine in adolescent rats

Chronic use of psychostimulants such as methylphenidate (MPD) and amphetamine (Amph) leads to abuse and dependence. Cross-sensitization occurs when exposure to a drug causes a significant intensified response to a different drug as compared to the effect of the drug in subjects with no previous exposure. Cross-sensitization is used as an experimental correlate for a drug's potential to elicit dependence. The present study uses male and female adolescent rats to examine whether cross-sensitization occurs with MPD, a drug not traditionally considered to elicit dependence, and Amph, a drug considered to elicit dependence. The results showed that there is cross-sensitization with MPD to Amph in adolescent rats and that there is a significant difference in male and female responses. Cross-sensitization between MPD and Amph was observed in a linear dose dependent manner in males and in an inverted U-shape pattern in females. Males treated with the highest dose of 10.0 mg/kg MPD and females treated with the mid-dose of 2.5 mg/kg MPD showed the most robust cross-sensitization. Overall, adolescent female rodents had a greater intensity of response to MPD, Amph, and cross-sensitization between MPD and Amph. This study shows that there are significant sex differences in psychostimulant cross-sensitization in adolescence, indicating the maturity of the gonadal system is not the predominant reason for differences between male and female responses to psychostimulant drugs.

Effects of noncontingent ethanol, DHEA, and pregnanolone administration on ethanol self-administration in outbred female rats

Previous research from this laboratory demonstrated that male outbred rats (Long-Evans) can be trained to prefer ethanol (10% v/v) over water during 30-min home-cage sessions and that higher ethanol concentrations (18-32% v/v) can serve as a reinforcer under various operant schedules. Further, we have shown that two neurosteroids, dehydroepiandrosterone (DHEA) and pregnanolone, can readily decrease ethanol self-administration in males. The present study used the same procedures in an attempt to systematically replicate the previous findings in female outbred rats. Rats were first trained to self-administer ethanol in the home cage using a saccharin-fading procedure. Subsequently, a two-bottle preference test was initiated by substituting different ethanol concentrations after subjects reliably consumed 10% ethanol alone. Water was always available during this phase. Next, subjects were transitioned to a fixed-ratio 10 (FR-10) schedule of reinforcement with 0.1 mL of ethanol (18% v/v) serving as the reinforcer so that a concentration-effect curve could be established. Upon completion, subjects were transitioned to an FR-10 FR-20 multiple schedule of ethanol (32% v/v) and food reinforcement to determine whether noncontingent ethanol, DHEA, and pregnanolone could selectively decrease ethanol intake. Not surprisingly, female subjects preferentially consumed ethanol over water at concentrations of 3.2-18% (v/v) during the home-cage procedure, and significantly increased the mean dose of ethanol consumed and blood ethanol concentration (BEC). Similarly, increasing concentrations under an FR-10 schedule significantly increased the dose of ethanol presented and BEC compared to control (water). Finally, under the multiple schedule, noncontingent injections of ethanol (0.32-1.8 g/kg), DHEA (10-100 mg/kg), and pregnanolone (1.8-32 mg/kg) dose-dependently decreased food- and ethanol-maintained responding and the dose of ethanol presented. BEC was significantly decreased by the neurosteroids, but increased by ethanol due to its noncontingent administration. Together, these data replicate only a subset of the data previously obtained in males, suggesting there are sex differences particularly with respect to the effects of DHEA and pregnanolone.

Trying to make sense of rodents' drug choice behavior

Since the first experimental hint for the existence of "an actual desire or striving for the drug" in nonhuman animals by Sidney Spragg in the late 1930s, much effort has been expended by lab researchers to try to model in a valid manner the key behavioral aspects and signs of addiction in animals, typically in rodents (i.e., mainly rats and, to a lesser extent, mice). Despite much advances, there still remains a lingering doubt about the disordered status of drug use in rodents. This is mainly because drug use occurs in a particular setting where animals have access to a drug for self-administration but without access to other valuable behavioral options that could compete with and divert from drug use. Here I review evidence showing that enriching the drug setting with other behavioral options can dramatically influence the pattern of drug choices in rodents. Overall, access to other options during drug access can divert the vast majority of rats from continued drug use. Only few individuals continue to engage in drug use despite access to and at the expense of other options. However, there exist certain high-risk settings in which virtually all animals are vulnerable to develop a harmful pattern of exclusive drug use that can even become fatal in the long run if not discontinued by an outside intervention. Paradoxically, it appears that the behavioral trait that is hypothesized to uniquely render rodents vulnerable to the latter settings (i.e., a narrow focus on the local, current choice, with no consideration of the global pattern of choice) would also protect most of them from using drugs in other choice settings. I conclude with an attempt to make sense of this peculiar setting-specific behavior and with some general propositions for future research.

Effect of enriched environment during adolescence on spatial learning and memory, and voluntary consumption of morphine in maternally separated rats in adulthood

This study was designed to examine the effect of environmental enrichment (EE) during adolescence on spatial learning and memory and voluntary morphine consumption in maternally separated (MS) male and female rats in adulthood. Male Wistar rats were allowed to mate with female virgin Wistar rats. Pups were separated from the dams daily for 180 min during postnatal days 2-14. All pups were weaned on day 21. The pups of both sexes were reared in a standard (SE) or enriched (EE) environment during postnatal days 21-50. Then, adulthood rats were tested for spatial learning and memory (Morris Water Maze), and voluntary consumption of morphine using a two-bottle choice paradigm (TBC). We found that the MS/SE rats showed longer escape latencies to find the platform on the third (the male) and fourth (the female) days of training than No MS/SE rats. Also, exposure to EE shortened the latency to escape in the male and female MS rats as training progressed than MS/SE rats. Moreover, the No MS/EE and MS/EE male rats spent significantly more time in the target zone compared with the SE control groups in the probe test. We also found that voluntary morphine consumption was higher in the male and female MS/SE than No MS/SE rats, while it was lower in the male and female MS/EE rats. The present results have shown that EE treatment may have potential therapeutic application for the prevention of the development of drug addiction and recovery from cognitive deficits following neonatal MS during adulthood.

The Modulating Role of Sex and Anabolic-Androgenic Steroid Hormones in Cannabinoid Sensitivity

Cannabis is the most commonly used illicit drug worldwide. Although its use is associated with multiple adverse health effects, including the risk of developing addiction, recreational and medical cannabis use is being increasing legalized. In addition, use of synthetic cannabinoid drugs is gaining considerable popularity and is associated with mass poisonings and occasional deaths. Delineating factors involved in cannabis use and addiction therefore becomes increasingly important. Similarly to other drugs of abuse, the prevalence of cannabis use and addiction differs remarkably between males and females, suggesting that sex plays a role in regulating cannabinoid sensitivity. Although it remains unclear how sex may affect the initiation and maintenance of cannabis use in humans, animal studies strongly suggest that endogenous sex hormones modulate cannabinoid sensitivity. In addition, synthetic anabolic-androgenic steroids alter substance use and further support the importance of sex steroids in controlling drug sensitivity. The recent discovery that pregnenolone, the precursor of all steroid hormones, controls cannabinoid receptor activation corroborates the link between steroid hormones and the endocannabinoid system. This article reviews the literature regarding the influence of endogenous and synthetic steroid hormones on the endocannabinoid system and cannabinoid action.

Social defeat stress and escalation of cocaine and alcohol consumption: Focus on CRF

Both the ostensibly aversive effects of unpredictable episodes of social stress and the intensely rewarding effects of drugs of abuse activate the mesocorticolimbic dopamine systems. Significant neuroadaptations in interacting stress and reward neurocircuitry may underlie the striking connection between stress and substance use disorders. In rodent models, recurring intermittent exposure to social defeat stress appears to produce a distinct profile of neuroadaptations that translates most readily to the repercussions of social stress in humans. In the present review, preclinical rodent models of social defeat stress and subsequent alcohol, cocaine or opioid consumption are discussed with regard to: (1) the temporal pattern of social defeat stress, (2) male and female protocols of social stress-escalated drug consumption, and (3) the neuroplastic effects of social stress, which may contribute to escalated drug-taking. Neuroadaptations in corticotropin-releasing factor (CRF) and CRF modulation of monoamines in the ventral tegmental area and the bed nucleus of the stria terminalis are highlighted as potential mechanisms underlying stress-escalated drug consumption. However, the specific mechanisms that drive CRF-mediated increases in dopamine require additional investigation as do the stress-induced neuroadaptations that may contribute to the development of compulsive patterns of drug-taking.

Interactions between estrogen receptors and metabotropic glutamate receptors and their impact on drug addiction in females

Contribution to Special Issue on Fast effects of steroids. Estrogen receptors α and β (ERα and ERβ) have a unique relationship with metabotropic glutamate receptors (mGluRs) in the female rodent brain such that estradiol is able to recruit intracellular G-protein signaling cascades to influence neuronal physiology, structure, and ultimately behavior. While this association between ERs and mGluRs exists in many cell types and brain regions, its effects are perhaps most striking in the nucleus accumbens (NAc). This review will discuss the original characterization of ER/mGluR signaling and how estradiol activity in the NAc confers increased sensitivity to drugs of abuse in females through this mechanism.

Social Defeat Stress, Sex, and Addiction-Like Behaviors

Social confrontation is a form of social interaction in animals where two conspecific individuals confront each other in dispute over territory, during the formation of hierarchies, and during breeding seasons. Typically, a social confrontation involves a prevailing individual and a yielding individual. The prevailing individual often exhibits aggressive postures and launches attacks, whereas the yielding individual often adopts postures of defeat. The yielding or defeated animals experience a phenomenon known as social defeat stress, in which they show exaggerated stress as well as autonomic and endocrine responses that cause impairment of both the brain and body. In laboratory settings, one can reliably generate social defeat stress by allowing a naïve (or already defeated) animal to intrude into a home cage in which its resident has already established a territory or is nursing. This resident-intruder paradigm has been widely used in both males and females to study mechanisms in the brain that underlie the stress responses. Stress has profound effects on drug reward for cocaine, methamphetamine, alcohol, and opioids. Particularly, previous experiences with social defeat can exaggerate subsequent addiction-like behaviors. The extent of these addiction-like behaviors depends on the intensity, duration, frequency, and intermittency of the confrontation episodes. This chapter describes four types of social defeat stress: acute, repeated, intermittent, and chronic. Specifically, it focuses on social defeat stress models used in laboratories to study individual, sex, and animal strain differences in addiction-like behaviors.