Sex differences and ovarian hormones in animal models of drug dependence

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.

Sex steroid hormones, the estrous cycle, and rapid modulation of glutamatergic synapse properties in the striatal brain regions with a focus on 17β-estradiol and the nucleus accumbens

The striatal brain regions encompassing the nucleus accumbens core (NAcc), shell (NAcs) and caudate-putamen (CPu) regulate cognitive functions including motivated behaviors, habit, learning, and sensorimotor action, among others. Sex steroid hormone sensitivity and sex differences have been documented in all of these functions in both normative and pathological contexts, including anxiety, depression and addiction. The neurotransmitter glutamate has been implicated in regulating these behaviors as well as striatal physiology, and there are likewise documented sex differences in glutamate action upon the striatal output neurons, the medium spiny neurons (MSNs). Here we review the available data regarding the role of steroid sex hormones such as 17β-estradiol (estradiol), progesterone, and testosterone in rapidly modulating MSN glutamatergic synapse properties, presented in the context of the estrous cycle as appropriate. Estradiol action upon glutamatergic synapse properties in female NAcc MSNs is most comprehensively discussed. In the female NAcc, MSNs exhibit development period-specific sex differences and estrous cycle variations in glutamatergic synapse properties as shown by multiple analyses, including that of miniature excitatory postsynaptic currents (mEPSCs). Estrous cycle-differences in NAcc MSN mEPSCs can be mimicked by acute exposure to estradiol or an ERα agonist. The available evidence, or lack thereof, is also discussed concerning estrogen action upon MSN glutamatergic synapse in the other striatal regions as well as the underexplored roles of progesterone and testosterone. We conclude that there is strong evidence regarding estradiol action upon glutamatergic synapse function in female NAcs MSNs and call for more research regarding other hormones and striatal regions.

Subregion specific neuroadaptations in the female rat striatum during acute and protracted withdrawal from nicotine

Epidemiological studies and clinical observations suggest that nicotine, a major contributor of the global burden of disease, acts in a partially sex specific manner. Still, preclinical research has primarily been conducted in males. More research is thus required to define the effects displayed by nicotine on the female brain. To this end, female rats received 15 injections of either nicotine (0.36mg/kg) or saline, over a 3-week period and were then followed for up to 3 months. Behavioral effects of nicotine were assessed using locomotor activity measurements and elevated plus maze, while neurophysiological changes were monitored using ex vivo electrophysiological field potential recordings conducted in subregions of the dorsal and ventral striatum. Behavioral assessments demonstrated a robust sensitization to the locomotor stimulatory properties of nicotine, but monitored behaviors on the elevated plus maze were not affected during acute (24 h) or protracted (3 months) withdrawal. Electrophysiological recordings revealed a selective increase in excitatory neurotransmission in the nucleus accumbens shell and dorsomedial striatum during acute withdrawal. Importantly, accumbal neuroadaptations in nicotine-treated rats correlated with locomotor behavior, supporting a role for the nucleus accumbens in behavioral sensitization. While no sustained neuroadaptations were observed following 3 months withdrawal, there was an overall trend towards reduced inhibitory tone. Together, these findings suggest that nicotine produces selective transformations of striatal brain circuits that may drive specific behaviors associated with nicotine exposure. Furthermore, our observations suggest that sex-specificity should be considered when evaluating long-term effects by nicotine on the brain.

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.

Synaptic remodeling of GluA1 and GluA2 expression in the nucleus accumbens promotes susceptibility to cognitive deficits concomitant with downstream GSK3β mediated neurotoxicity in female mice during abstinence from voluntary oral methamphetamine

Stimulant-use disorders can present with long-term cognitive and mental health deficits. Little is known about the underlying molecular mechanisms perpetuating sex differences in cognitive and behavioral deficits in preclinical models of addiction to stimulants such as methamphetamine (MA). The current study investigated the neurochemical shifts underlying sex disparities in MA-induced working memory deficits and an addictive phenotype following abstinence from chronic MA abuse. We used our previously reported mouse model of voluntary oral methamphetamine administration (VOMA) consisting of an acquisition phase (days 1-14) characterized by escalating doses of MA and a binge phase (days 14-28) characterized by static doses. Female VOMA mice exhibited sustained MA consumption during the binge phase, demonstrating sex-specific vulnerabilities to the maintenance of MA addiction. The 8-arm radial maze was used to test spatial working memory performance following abstinence from VOMA. Results indicate working memory deficits correlated to higher MA consumption in females only. Hippocampal and accumbal tissue were collected and analyzed by immunoblotting. Female VOMA mice had decreased GluA1, but not GluA2, in the hippocampus, which may perpetuate synaptic destabilization and working memory deficits. Female-specific increases in GluA1 and p-GSK3β expression in accumbal tissue suggest vulnerability toward abstinence-induced drug craving and heightened downstream neurotoxicity. Our study reveals female-specific neurochemical shifts in hippocampal and accumbal AMPA receptor signaling following abstinence from chronic MA consumption that may perpetuate female susceptibility to MA-induced cognitive deficits. These data demonstrate a novel molecular pathway that would exacerbate memory deficits and perpetuate an addictive phenotype in female populations following MA abuse.

Preliminary evidence of increased alcohol use associated with ethinyl estradiol levels in women using oral contraceptives

Alcohol use is highly prevalent in young adult women and rates of alcohol use disorder are rising rapidly in this population. Further, emerging evidence suggests that circulating levels of ovarian hormones influence alcohol consumption, with increased consumption associated with higher estradiol and lower progesterone levels. However, less is known about the influence of synthetic hormones (contained in oral contraceptive (OC) pills) on alcohol use. The current study examined the influence of OC pill phase, ethinyl estradiol (EE) levels, and progestin levels on self-reported alcohol consumption in healthy female drinkers. Young adult female drinkers using OCs (N = 21) reported alcohol use across one OC pill pack using the Timeline Followback and provided blood samples during both pill phases to measure synthetic hormone levels. We compared alcohol use between OC pill phases (active vs. inactive) using linear mixed effects models for repeated measures and examined correlations between alcohol use and EE and progestin levels. Results showed that women with higher EE levels reported increased alcohol consumption (r = 0.56, p = 0.01) and binge drinking (r = 0.45, p = 0.04) in the active pill phase. Progestin levels and pill phase were not significantly associated with alcohol consumption. These findings provide preliminary data suggesting increased levels of EE from OC pills are associated with excessive alcohol consumption in women. Further research is needed to determine if EE plays a causal role in increased alcohol consumption. This line of research could inform female-specific AUD prevention and treatment strategies among the large subpopulation of women using hormonal contraceptives.

Methodological approach for an integrated female-specific study of anxiety and smoking comorbidity

Two primary ovarian hormones that fluctuate across the female menstrual cycle-estradiol and progesterone-have been independently linked in separate literatures to nicotine reinforcement and anxiety psychopathology. We identify existing methodological limitations in these literatures, describe an example protocol that was developed to address such limitations, highlight case examples, and offer insights on the resulting advantages and challenges. This protocol was an observational, prospective, within-subjects study of female cigarette smokers who were followed over the course of a complete menstrual cycle. Non-treatment seeking, female cigarette smokers (N = 50), between the ages of 18-40 who have a normal menstrual cycle (25-35 days in length) were recruited from the community. Females with anxiety or mood psychopathology represented 38.0% of the sample. Salivary progesterone and estradiol were assessed each morning via at-home saliva collection methods. Self-reported within-day momentary ratings of anxiety and nicotine reinforcement were collected using ecological momentary assessment (EMA) via a mobile app. Protocol compliance was >85%. Within- and between-subjects heterogeneity was observed in the progesterone and estradiol, anxiety, and nicotine craving measures, especially in the context of anxiety psychopathology. We aimed to integrate the anxiety and nicotine dependence literatures and advance the empirical study of the role of ovarian hormones. This protocol reflects an intensive, yet feasible approach to collecting daily-level naturalistic data related to estradiol, progesterone, anxiety, and nicotine reinforcement.

Stress and gonadal steroid influences on alcohol drinking and withdrawal, with focus on animal models in females

Sexually dimorphic effects of alcohol, following binge drinking, chronic intoxication, and withdrawal, are documented at the level of the transcriptome and in behavioral and physiological responses. The purpose of the current review is to update and to expand upon contributions of the endocrine system to alcohol drinking and withdrawal in females, with a focus on animal models. Steroids important in the hypothalamic-pituitary-gonadal and hypothalamic-pituitary-adrenal axes, the reciprocal interactions between these axes, the effects of chronic alcohol use on steroid levels, and the genomic and rapid membrane-associated effects of steroids and neurosteroids in models of alcohol drinking and withdrawal are described. Importantly, comparison between males and females highlight some divergent effects of sex- and stress-steroids on alcohol drinking- and withdrawal-related behaviors, and the distinct differences in response emphasize the importance of considering sex in the development of novel pharmacotherapies for the treatment of alcohol use disorder.

Aversion-associated drug and alcohol seeking in females

Compulsive drug intake is characterized by the continuation of use regardless of negative consequences. This is modeled preclinically using procedures where a negative stimulus is delivered contingently with consumption of the reinforcer. In humans, women and men exhibit different drug taking behavior as it pertains to overall use, withdrawal symptoms, and rate of dependence. In substance use research, females have often been excluded from many studies due to concerns that circulating sex hormones may affect drug seeking behavior. However, the more recent inclusion of females in preclinical studies has identified interesting sex differences in aversion-resistant intake of drugs and alcohol. This review will serve to summarize key findings in aversion-related intake of alcohol, psychostimulants, and opioids in females by examining studies that have included female subjects. Further discussion will examine the effect of intake model, neuroanatomical pathways, and sex hormones in the expression of aversion-resistant drug and alcohol consumption.

Estrous cycle dependent expression of oxycodone conditioned reward in rats

Oxycodone is one of the most widely prescribed and misused opioid painkillers in the United States. Evidence suggests that biological sex and hormonal status can impact drug reward in humans and rodents, but the extent to which these factors can influence the rewarding effects of oxycodone is unclear. The purpose of this study was to utilize place conditioning to determine the effects of sex and female hormonal status on the expression of oxycodone conditioned reward in rats. Gonadally intact adult Sprague-Dawley male and female rats were used to test: (1) whether both sexes express conditioned reward to oxycodone at similar doses, (2) the impact of conditioning session length on oxycodone conditioned reward expression in both sexes, and (3) the influence of female estrous cycle stage on oxycodone conditioned reward expression. Both sexes expressed conditioned reward at the same doses of oxycodone. Increasing the length of conditioning sessions did not reveal an effect of sex and resulted in lower magnitude conditioned reward expression. Importantly however, female stage of estrous cycle significantly influenced oxycodone conditioned reward expression. These results suggest that female hormonal status can impact the rewarding effects of opioids and thus have important implications for prescription opioid treatment practices.

The importance of translationally evaluating steroid hormone contributions to substance use

Clinically, women appear to be more susceptible to certain aspects of substance use disorders (SUDs). The steroid hormones 17β-estradiol (E2) and progesterone (Pg) have been linked to women-specific drug behaviors. Here, we review clinical and preclinical studies investigating how cycling ovarian hormones affect nicotine-, cocaine-, and opioid-related behaviors. We also highlight gaps in the literature regarding how synthetic steroid hormone use may influence drug-related behaviors. In addition, we explore how E2 and Pg are known to interact in brain reward pathways and provide evidence of how these interactions may influence drug-related behaviors. The synthesis of this review demonstrates the critical need to study women-specific factors that may influence aspects of SUDs, which may play important roles in addiction processes in a sex-specific fashion. It is important to understand factors that impact women's health and may be key to moving the field forward toward more efficacious and individualized treatment strategies.

Effects of the estrous cycle on impulsive choice and interval timing in female rats

Research in humans and animals shows differences in impulsive choice, which is a failure to wait for larger, delayed rewards, when comparing males and females. It is possible that fluctuations in sex hormones (estradiol and progesterone) across the reproductive cycle contribute to sex differences in impulsive choice. The current study delivered an impulsive choice task with peak interval trials to female rats while estrous cycles, the rodent reproductive cycle, were tracked over the course of the task. Female rats were more sensitive to changes in delay in the proestrus phase of the estrous cycle and made more larger-later choices when in estrus, particularly when the delay to the smaller reward was short. Estradiol increases dramatically during proestrus while progesterone peaks during estrus, suggesting that estradiol and progesterone may affect impulsive choice through mechanisms such as delay discounting, delay aversion, and/or timing processes. Analyses of timing of the choice task delays showed inconsistent effects of the estrous cycle across delays, suggesting that reward-timing interactions may have complicated how hormone fluctuations affected interval timing. Further research is needed to determine the mechanism underlying increased larger-later choices during the estrus phase, increased delay sensitivity during the proestrus phase, and variability in interval timing across delays and estrous cycle stages.

Elucidating the reinforcing effects of nicotine: a tribute to Nadia Chaudhri

Nadia Chaudhri worked with us as a graduate student in the Center for Neuroscience at the University of Pittsburgh from 1999 until she earned her PhD in 2005, a time that coincided with the discovery in our lab of the dual reinforcing actions of nicotine, a concept that she played an important role in shaping. The research that was described in her doctoral thesis is among the foundational pillars of the now well-accepted notion that nicotine acts as both a primary reinforcer and an amplifier of other reinforcer stimuli. This reinforcement-enhancing action of nicotine is robust and likely to be a powerful driver of nicotine use. Below, we discuss the evidence that these two actions of nicotine - primary reinforcement and reinforcement enhancement - are distinct and dissociable, a finding that Nadia was closely associated with. We go on to address two other topics that greatly interested Nadia during that time, the generalizability of the reinforcement-enhancing action of nicotine to multiple classes of reinforcing stimuli and potential sex differences in the dual reinforcing actions of nicotine. The research has greatly expanded since Nadia's involvement, but the core ideas that she helped to develop remain central to the concept of the dual reinforcing actions of nicotine and its importance for understanding the drivers of nicotine use.

ERα Stimulation Rapidly Modulates Excitatory Synapse Properties in Female Rat Nucleus Accumbens Core

INTRODUCTION

The nucleus accumbens core (NAcc) is a sexually differentiated brain region that is modulated by steroid hormones such as 17β-estradiol (estradiol), with consequential impacts on relevant motivated behaviors and disorders such as addiction, anxiety, and depression. NAcc estradiol levels naturally fluctuate, including during the estrous cycle in adult female rats, which is analogous to the menstrual cycle in adult humans. Across the estrous cycle, excitatory synapse properties of medium spiny neurons rapidly change, as indicated by analysis of miniature excitatory postsynaptic currents (mEPSCs). mEPSC frequency decreases during estrous cycle phases associated with high estradiol levels. This decrease in mEPSC frequency is mimicked by acute topical exposure to estradiol. The identity of the estrogen receptor (ER) underlying this estradiol action is unknown. Adult rat NAcc expresses three ERs, all extranuclear: membrane ERα, membrane ERβ, and GPER1.

METHODS

In this brief report, we take a first step toward addressing this challenge by testing whether activation of ERs via acute topical agonist application is sufficient for inducing changes in mEPSC properties recorded via whole-cell patch clamp.

RESULTS

An agonist of ERα induced large decreases in mEPSC frequency, while agonists of ERβ and GPER1 did not robustly modulate mEPSC properties.

CONCLUSIONS

These data provide evidence that activation of ERα is sufficient for inducing changes in mEPSC frequency and is a likely candidate underlying the estradiol-induced changes observed during the estrous cycle. Overall, these findings extend our understanding of the neuroendocrinology of the NAcc and implicate ERα as a primary target for future studies.

Reducing short- and long-term cocaine craving with voluntary exercise in male rats

BACKGROUND

In a previous study in female rats, voluntary wheel running attenuated incubation of cocaine craving after 30 but not 3 days (Zlebnik and Carroll Zlebnik and Carroll, Psychopharmacology 232:3507-3413, 2015). The present study in male rats, using the same procedure, showed that wheel running reduced incubated craving after both 30 and 3 days of abstinence.

METHODS

Male rats self-administered i.v. cocaine (0.4 mg/kg) during 6-h sessions for 10 days. They were then moved from the operant chamber to a home cage with an attached running wheel or stationary wheel, for 6 h daily for a 3- or 30-day period when cocaine craving was hypothesized to incubate. Rats were then returned to the operant chamber for a 30-min test of cocaine seeking, or "craving," indicated by responses on the former "drug" lever was formerly associated with drug stimulus lights and responses (vs. no drug stimuli), and lever responding was compared to responses on the "inactive" that was illuminated and counted lever pressing.

RESULTS

Mean wheel revolutions were similar across the 3- and 30-day incubation groups, when both groups of rats were given access to wheel running vs. access to a stationary wheel in controls. Subsequently, when rats were tested in the operant chamber for "relapse" responding (drug-lever responding) on the lever formerly associated with drug access, cocaine craving was reduced by recent running wheel access (vs. stationary wheel access) in both the 3- and 30-day wheel exposure groups.

CONCLUSION

Voluntary, self-initiated, and self-sustained physical exercise reduced cocaine craving after short- (3 days) and long-term (30 days) abstinence periods in male rats that previously self-administered cocaine. This was contrasted with reduction of cocaine seeking in females after 30-day, but not 3-day, incubation periods under the wheel running vs. stationary wheel conditions in a previous study (Zlebnik and Carroll Zlebnik and Carroll, Psychopharmacology 232:3507-3413, 2015). These initial findings suggest males may be more sensitive to incubated craving for cocaine than females.

Ranking the contribution of behavioral measures comprising oxycodone self-administration to reinstatement of drug-seeking in male and female rats

Introduction

Rates of relapse to drug use during abstinence are among the highest for opioid use disorder (OUD). In preclinical studies, reinstatement to drug-seeking has been extensively studied as a model of relapse-but the work has been primarily in males. We asked whether biological sex contributes to behaviors comprising self-administration of the prescription opioid oxycodone in rats, and we calculated the relative contribution of these behavioral measures to reinstatement in male and female rats.

Materials and methods

Rats were trained to self-administer oxycodone (8 days, training phase), after which we examined oxycodone self-administration behaviors for an additional 14 days under three conditions in male and female rats: short access (ShA, 1 h/d), long access (LgA, 6 h/d), and saline self-administration. All rats were then tested for cue-induced reinstatement of drug-seeking after a 14-d forced abstinence period. We quantified the # of infusions, front-loading of drug intake, non-reinforced lever pressing, inter-infusion intervals, escalation of intake, and reinstatement responding on the active lever.

Results

Both male and female rats in LgA and ShA conditions escalated oxycodone intake to a similar extent. However, males had higher levels of non-reinforced responding than females under LgA conditions, and females had greater levels of reinstatement responding than males. We then correlated each addiction-related measure listed above with reinstatement responding in males and females and ranked their respective relative contributions. Although the majority of behavioral measures associated with oxycodone self-administration did not show sex differences on their own, when analyzed together using partial least squares regression, their relative contributions to reinstatement were sex-dependent. Front-loading behavior was calculated to have the highest relative contribution to reinstatement in both sexes, with long and short inter-infusion intervals having the second greatest contribution in females and males, respectively.

Discussion

Our results demonstrate sex differences in some oxycodone self-administration measures. More importantly, we demonstrate that a sex- dependent constellation of self-administration behaviors can predict the magnitude of reinstatement, which holds great promise for relapse prevention in people.

Energy drinks and alcohol in a binge drinking protocol in Wistar rats: Male and female behavioral and reproductive effects

The consumption of energy drinks is common among adolescents and young adults. The possible effects (mainly behavioral and reproductive) of ingestion in this population remain unknown. For this reason, this study aimed to evaluate the behavioral and reproductive effects of energy drinks and their main constituents (caffeine and taurine), as well as their combinations with alcohol, via a binge drinking protocol in male and female Wistar rats during puberty. In this study, 100 male and 100 female rats were treated with a binge drinking protocol 3 days a week over 4 weeks from postnatal day (PND) 28 to PND 60, which included 10 mL/kg by oral gavage of distilled water, energy drink, caffeine (3.2 mg/kg), taurine (40 mg/kg), and their combinations with alcohol (2 g/kg). The animals were evaluated by behavioral tests from PND 56 to PND 60 (open field, plus maze and object recognition) and reproductive parameters (estrous cycle regularity, weight of sexual organs, oocyte quality, spermatid and sperm count, sperm morphology and testosterone level). Locomotor activity was increased in females in the groups combined with alcohol (except alcohol + caffeine) and in the caffeine group. Long-term memory was increased in males in the caffeine and taurine groups even when combined with alcohol. The combination of energy drinks and alcohol did not have significant effects on the reproductive parameters of either sex of rats during puberty. We concluded that energy drinks (and their main constituents) and alcohol combinations did not cause alterations in reproductive profiles, and locomotor activity and long-term memory were increased in females and males, respectively.

Genetics and epigenetics: paternal adolescent ethanol consumption in serotonin transporter knock-out rats and offspring sensitivity to ethanol

RATIONALE

Alcohol use disorder (AUD) is shown to have an overall heritability of around 50%. One of the genes associated with AUD is SLC6A4 (solute carrier family 6 member A4) which codes for the serotonin transporter (SERT). The study looked at serotonin dysfunction on ethanol consumption in adolescents and the subsequent intergenerational effects of drinking by using a rat model: SERT^+/+ (regular functioning), SERT^+/- (50% transporter reduction) and SERT^-/- (complete reduction).

OBJECTIVES

We investigated sex and genotype differences in ethanol consumption in SERT knock-out Wistar rats (F0) followed by studying behaviour in the offspring (F1) of the male drinkers to assess effects of paternal alcohol consumption.

METHODS

An intermittent access two-bottle choice paradigm (IA2BC) was used to yield ethanol drinking behaviour in F0 adolescent Wistar rats. The highest drinking males were mated to alcohol-naive females and their offspring were compared with controls. Drinking behaviour (IA2BC) and ethanol-induced motor coordination effects (via rotarod) were measured in the F1s.

RESULTS

F0 drinking saw no SERT genotype differences in males. However, females consumed higher volumes of ethanol compared to males, with SERT^-/- females showing the highest intake. A clearer genotype effect was seen in the F1 animals, with reduction in SERT activity leading to enhanced ethanol intake in both sexes. Importantly, paternal exposure to ethanol significantly reduced the ethanol induced motor side effects in offspring, independent of sex and genotype.

CONCLUSIONS

These indicate a difference in the way genetic factors may act across sexes and suggest the involvement of epigenetic mechanisms in the intergenerational effects of alcohol.

Regulation of sex differences in risk-based decision making by gonadal hormones: Insights from rodent models

Men and women differ in their ability to evaluate options that vary in their rewards and the risks that are associated with these outcomes. Most studies have shown that women are more risk averse than men and that gonadal hormones significantly contribute to this sex difference. Gonadal hormones can influence risk-based decision making (i.e., risk taking) by modulating the neurobiological substrates underlying this cognitive process. Indeed, estradiol, progesterone and testosterone modulate activity in the prefrontal cortex, amygdala and nucleus accumbens associated with reward and risk-related information. The use of animal models of decision making has advanced our understanding of the intersection between the behavioral, neural and hormonal mechanisms underlying sex differences in risk taking. This review will outline the current state of this literature, identify the current gaps in knowledge and suggest the neurobiological mechanisms by which hormones regulate risky decision making. Collectively, this knowledge can be used to understand the potential consequences of significant hormonal changes, whether endogenously or exogenously induced, on risk-based decision making as well as the neuroendocrinological basis of neuropsychiatric diseases that are characterized by impaired risk taking, such as substance use disorder and schizophrenia.

The estrous cycle and 17β-estradiol modulate the electrophysiological properties of rat nucleus accumbens core medium spiny neurons

The nucleus accumbens core is a key nexus within the mammalian brain for integrating the premotor and limbic systems and regulating important cognitive functions such as motivated behaviors. Nucleus accumbens core functions show sex differences and are sensitive to the presence of hormones such as 17β-estradiol (estradiol) in normal and pathological contexts. The primary neuron type of the nucleus accumbens core, the medium spiny neuron (MSN), exhibits sex differences in both intrinsic excitability and glutamatergic excitatory synapse electrophysiological properties. Here, we provide a review of recent literature showing how estradiol modulates rat nucleus accumbens core MSN electrophysiology within the context of the estrous cycle. We review the changes in MSN electrophysiological properties across the estrous cycle and how these changes can be mimicked in response to exogenous estradiol exposure. We discuss in detail recent findings regarding how acute estradiol exposure rapidly modulates excitatory synapse properties in nucleus accumbens core but not caudate-putamen MSNs, which mirror the natural changes seen across estrous cycle phases. These recent insights demonstrate the strong impact of sex-specific estradiol action upon nucleus accumbens core neuron electrophysiology.

Assessing negative affect in mice during abstinence from alcohol drinking: Limitations and future challenges

Alcohol use disorder (AUD) is frequently comorbid with mood disorders, and these co-occurring neuropsychiatric disorders contribute to the development and maintenance of alcohol dependence and relapse. In preclinical models, mice chronically exposed to alcohol display anxiety-like and depressive-like behaviors during acute withdrawal and protracted abstinence. However, in total, results from studies using voluntary alcohol-drinking paradigms show variable behavioral outcomes in assays measuring negative affective behaviors. Thus, the main objective of this review is to summarize the literature on the variability of negative affective behaviors in mice after chronic alcohol exposure. We compare the behavioral phenotypes that emerge during abstinence across different exposure models, including models of alcohol and stress interactions. The complicated outcomes from these studies highlight the difficulties of assessing negative affective behaviors in mouse models designed for the study of AUD. We discuss new behavioral assays, comprehensive platforms, and unbiased machine-learning algorithms as promising approaches to better understand the interaction between alcohol and negative affect in mice. New data-driven approaches in the understanding of mouse behavior hold promise for improving the identification of mechanisms, cell subtypes, and neurocircuits that mediate negative affect. In turn, improving our understanding of the neurobehavioral basis of alcohol-associated negative affect will provide a platform to test hypotheses in mouse models that aim to improve the development of more effective strategies for treating individuals with AUD and co-occurring mood disorders.

Feasibility and acceptability of testing a menstrual-cycle timed smoking cessation intervention for women of reproductive age (Project Phase): Results of a pilot randomized control trial

INTRODUCTION

Menstrual phase influences cigarette smoking-related outcomes. Telephone-based cessation programs (e.g., quitlines) may incorporate the role of the menstrual cycle in an effort to tailor interventions for women.

PURPOSE

The goal of this preliminary randomized clinical trial was to examine the feasibility and acceptability of timing quit date to menstrual phase in women in a quitline setting.

METHODS

We recruited treatment-seeking women with regular menstrual cycles between the ages of 18-40 years. Participants were randomized to the follicular phase (FP; quit date set 6-8 days post onset of menses) or standard of care (SC; no menstrual timing of quit date). All participants received four weeks of nicotine replacement therapy transdermal patch concurrent with six weeks of telephone-based counseling. We explored self-reported and biochemically-verified seven-day point prevalence abstinence at end-of-treatment and three-month follow-up.

RESULTS

Participants (n = 119; FP: n = 58, SC: n = 61) were, on average, 33.4 years old and smoked 13.6 cigarettes/day. The median number of counseling sessions completed was 6 out of 6 available, and 66% of participants completed the intervention. Over 90% of participants reported they would recommend this study to friends/family. Cessation rates did not significantly vary by randomization.

CONCLUSIONS

Results of this preliminary trial indicate that timing quit date to FP is an acceptable and feasible approach to address smoking cessation in women of reproductive age. While we observed similar smoking cessation rates between groups, this preliminary study was not fully powered to determine efficacy. Therefore, the feasibility and acceptability results indicate that a fully-powered efficacy trial is warranted.

Sex differences in sucrose reinforcement in Long-Evans rats

Background

There are sex differences in addiction behaviors. To develop a pre-clinical animal model to investigate this, the present study examined sex differences in sucrose taking and seeking using Long-Evans rats.

Methods

Five experiments were conducted using separate groups of subjects. The first two examined sucrose or saccharin preference in two-bottle home cage choice tests. Experiment three assessed sucrose intake in a binge model with sucrose available in home cage bottles. Experiments four and five utilized operant-based procedures. In experiment four rats responded for sucrose on fixed and progressive ratio (FR, PR) schedules of reinforcement over a range of concentrations of sucrose. A final component of experiment four was measuring seeking in the absence of sucrose challenged with the dopamine D1 receptor antagonist SCH23390. Experiment five assessed responding for water on FR and PR schedules of reinforcement.

Results

When accounting for body weight, female rats consumed more sucrose than water; but there was no sex difference in saccharin preference over a range of saccharin concentrations. When accounting for body weight, females consumed more sucrose than males in the binge model, and only females increased binge intake over 14 days of the study. Females responded at higher rates for sucrose under both FR and PR schedules of reinforcement. Females responded at higher rates in extinction (seeking); SCH23390 reduced sucrose seeking of both females and males. Females responded at higher rates for water on FR and PR schedules than males, although rates of responding were low and decreased over sessions.

Conclusions

Across bottle-choice, binge intake, and operant procedures, female Long-Evans rats consumed more sucrose and responded at higher rates for sucrose. Although females also responded more for water, the vigor of responding did not explain the consistent sex difference in sucrose taking and seeking. The sex difference in sucrose taking was also not explained by sweet preference, as there was no sex difference in saccharin preference. These data provide a pre-clinical model to further evaluate sex differences in addiction behaviors and manipulations designed to reduce them.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13293-022-00412-8.

Factors modulating the incubation of drug and non-drug craving and their clinical implications

It was suggested in 1986 that cue-induced cocaine craving increases progressively during early abstinence and remains high during extended periods of time. Clinical evidence now supports this hypothesis and that this increase is not specific to cocaine but rather generalize across several drugs of abuse. Investigators have identified an analogous incubation phenomenon in rodents, in which time-dependent increases in cue-induced drug seeking are observed after abstinence from intravenous drug or palatable food self-administration. Incubation of craving is susceptible to variation in magnitude as a function of biological and/or the environmental circumstances surrounding the individual. During the last decade, the neurobiological correlates of the modulatory role of biological (sex, age, genetic factors) and environmental factors (environmental enrichment and physical exercise, sleep architecture, acute and chronic stress, abstinence reinforcement procedures) on incubation of drug craving has been investigated. In this review, we summarized the behavioral procedures adopted, the key underlying neurobiological correlates and clinical implications of these studies.

Sex Differences and Exogenous Estrogen Influence Learning and Brain Responses to Prediction Errors

Animal studies show marked sex differences as well as effects of estrogen (E2) in the mesocorticolimbic dopaminergic (DA) pathways, which play a critical role in reward processing and reinforcement learning and are also implicated in drug addiction. In this computational pharmacological fMRI study, we investigate the effects of both factors, sex and estrogen, on reinforcement learning and the dopaminergic system in humans; 67 male and 64 naturally cycling female volunteers, the latter in their low-hormone phase, were randomly assigned, double-blind, to take E2 or placebo. They completed a reinforcement learning task in the MRI scanner for which we have previously shown reward prediction error (RPE)-related activity to be dopaminergic. We found RPE-related brain activity to be enhanced in women compared with men and to a greater extent when E2 levels were elevated in both sexes. However, both factors, female sex and E2, slowed adaptation to RPEs (smaller learning rate). This discrepancy of larger RPE-related activity yet smaller learning rates can be explained by organizational sex differences and activational effects of circulating E2, which both affect DA release differently to DA receptor binding capacities.

Effects of Sex and Estrous Cycle on the Time Course of Incubation of Cue-Induced Craving following Extended-Access Cocaine Self-Administration

Cocaine addiction is a devastating public health epidemic that continues to grow. Studies focused on identifying biological factors influencing cocaine craving and relapse vulnerability are necessary to promote abstinence in recovering drug users. Sex and ovarian hormones are known to influence cocaine addiction liability and relapse vulnerability in both humans and rodents. Previous studies have investigated sex differences in the time-dependent intensification or "incubation" of cue-induced cocaine craving that occurs during withdrawal from extended-access cocaine self-administration and have identified changes across the rat reproductive cycle (estrous cycle). Female rats in the estrus stage of the cycle (Estrus Females), the phase during which ovulation occurs, show an increase in the magnitude of incubated cue-induced cocaine craving compared with females in all other phases of the estrous cycle (Non-Estrus Females). Here we extend these findings by assessing incubated craving across the estrous cycle during earlier withdrawal periods (withdrawal day 1 and 15) and later withdrawal periods (withdrawal day 48). We found that this increase in the magnitude of incubated craving during estrus (Estrus Females) is present on withdrawal day 15, but not on withdrawal day 1, and further increases by withdrawal day 48. No difference in the magnitude of incubated craving was observed between Males and Non-Estrus Females. Our data indicate that the effects of hormonal fluctuations on cue-induced cocaine craving intensify during the first month and a half of withdrawal, showing an interaction among abstinence length, estrous cycle fluctuations, and cocaine craving.

Effects of Withdrawal from Cocaine Self-Administration on Rat Orbitofrontal Cortex Parvalbumin Neurons Expressing Cre recombinase: Sex-Dependent Changes in Neuronal Function and Unaltered Serotonin Signaling

The orbitofrontal cortex (OFC) is a brain region involved in higher-order decision-making. Rodent studies show that cocaine self-administration (CSA) reduces OFC contribution to goal-directed behavior and behavioral strategies to avoid drug intake. This change in OFC function persists for many weeks after cocaine withdrawal, suggesting involvement in the process of addiction. The mechanisms underlying impaired OFC function by cocaine are not well-understood. However, studies implicate altered OFC serotonin (5-HT) function in disrupted cognitive processes during addiction and other psychiatric disorders. Thus, it is hypothesized that cocaine impairment of OFC function involves changes in 5-HT signaling, and previous work shows that 5-HT_1A and 5-HT_2A receptor-mediated effects on OFC pyramidal neurons (PyNs) are impaired weeks after cocaine withdrawal. However, 5-HT effects on other contributors to OFC circuit function have not been fully investigated, including the parvalbumin-containing, fast-spiking interneurons (OFC^PV), whose function is essential to normal OFC-mediated behavior. Here, 5-HT function in naive rats and those withdrawn from CSA were evaluated using a novel rat transgenic line in which the rat parvalbumin promoter drives Cre-recombinase expression to permit identification of OFC^PV cells by fluorescent reporter protein expression. We find that whereas CSA altered basal synaptic and membrane properties of the OFC^PV neurons in a sex-dependent manner, the effects of 5-HT on these cells were unchanged by CSA. These data suggest that the behavioral effects of dysregulated OFC 5-HT function caused by cocaine experience are primarily mediated by changes in 5-HT signaling at PyNs, and not at OFC^PV neurons.

Impact of Acute and Chronic Cannabis Use on Stress Response Regulation: Challenging the Belief That Cannabis Is an Effective Method for Coping

Although research has only recently started to examine the impact of cannabis use on stress response, there is some evidence that indicates acute and chronic impacts of cannabis on these processes. In this paper, we review processes involved in regulating the stress response and we review the influence of acute and chronic exposure to cannabis on patterns and regulation of the stress response. We also highlight the role of stress as a risk factor for initiation and maintenance of cannabis use. In this context, we examine moderating variables, including sex and life adversity. In light of recent observations indicating increasing prevalence of cannabis use during pregnancy, we provide additional focus on cannabis use in this vulnerable population, including how acute and chronic stress may predispose some individuals to use cannabis during pregnancy. While this line of research is in its infancy, we review available articles that focus on the perinatal period and that examined the association between cannabis use and various life stressors, including partner violence, job loss, and lack of housing. We also review psychiatric co-morbidities (e.g., post-traumatic stress disorder, anxiety). A better understanding of the way stress and cannabis use relate within the general population, as well as within certain subgroups that may be at a greater risk of using and/or at greater risk for adverse outcomes of use, may lead to the development of novel prevention and intervention approaches.

Recent Perspectives on Sex Differences in Compulsion-Like and Binge Alcohol Drinking

Alcohol use disorder remains a substantial social, health, and economic problem and problem drinking levels in women have been increasing in recent years. Understanding whether and how the underlying mechanisms that drive drinking vary by sex is critical and could provide novel, more targeted therapeutic treatments. Here, we examine recent results from our laboratories and others which we believe provide useful insights into similarities and differences in alcohol drinking patterns across the sexes. Findings for binge intake and aversion-resistant, compulsion-like alcohol drinking are considered, since both are likely significant contributors to alcohol problems in humans. We also describe studies regarding mechanisms that may underlie sex differences in maladaptive alcohol drinking, with some focus on the importance of nucleus accumbens (NAcb) core and shell regions, several receptor types (dopamine, orexin, AMPA-type glutamate), and possible contributions of sex hormones. Finally, we discuss how stressors such as early life stress and anxiety-like states may interact with sex differences to contribute to alcohol drinking. Together, these findings underscore the importance and critical relevance of studying female and male mechanisms for alcohol and co-morbid conditions to gain a true and clinically useful understanding of addiction and neuropsychiatric mechanisms and treatment.

Cannabinoid CB1 receptor in dorsal telencephalic glutamatergic neurons drives overconsumption of palatable food and obesity

Palatable food can promote overfeeding beyond homeostatic requirements, thereby constituting a major risk to obesity. Here, the lack of cannabinoid type 1 receptor (CB1) in dorsal telencephalic glutamatergic neurons (Glu-CB1-KO) abrogated the overconsumption of palatable food and the development of obesity. On low-fat diet, no genotype differences were observed. However, under palatable food conditions, Glu-CB1-KO mice showed decreased body weight and food intake. Notably, Glu-CB1-KO mice were protected from alterations in the reward system after high-fat diet feeding. Interestingly, obese wild-type mice showed a superior olfactory detection as compared to mutant mice, suggesting a link between overconsumption of palatable food and olfactory function. Reconstitution of CB1 expression in olfactory cortex in high-fat diet-fed Glu-CB1-KO mice using viral gene delivery partially reversed the lean phenotype concomitantly with improved odor perception. These findings indicate that CB1 in cortical glutamatergic neurons regulates hedonic feeding, whereby a critical role of the olfactory cortex was uncovered as an underlying mechanism.

Repeated morphine exposure activates synaptogenesis and other neuroplasticity-related gene networks in the dorsomedial prefrontal cortex of male and female rats

BACKGROUND

Opioid abuse is a chronic disorder likely involving stable neuroplastic modifications. While a number of molecules contributing to these changes have been identified, the broader spectrum of genes and gene networks that are affected by repeated opioid administration remain understudied.

METHODS

We employed Next-Generation RNA-sequencing (RNA-seq) followed by quantitative chromatin immunoprecipitation to investigate changes in gene expression and their regulation in adult male and female rats' dorsomedial prefrontal cortex (dmPFC) after a regimen of daily injection of morphine (5.0 mg/kg; 10 days). Ingenuity Pathway Analysis (IPA) was used to analyze affected molecular pathways, gene networks, and associated regulatory factors. A complementary behavioral study evaluated the effects of the same morphine injection regimen on locomotor activity, pain sensitivity, and somatic withdrawal signs.

RESULTS

Behaviorally, repeated morphine injection induced locomotor hyperactivity and hyperalgesia in both sexes. 90 % of differentially expressed genes (DEGs) in morphine-treated rats were upregulated in both males and females, with a 35 % overlap between sexes. A substantial number of DEGs play roles in synaptic signaling and neuroplasticity. Chromatin immunoprecipitation revealed enrichment of H3 acetylation, a transcriptionally activating chromatin mark. Although broadly similar, some differences were revealed in the gene ontology networks enriched in females and males.

CONCLUSIONS

Our results cohere with findings from previous studies based on a priori gene selection. Our results also reveal novel genes and molecular pathways that are upregulated by repeated morphine exposure, with some common to males and females and others that are sex-specific.

Female rats display higher methamphetamine-primed reinstatement and c-Fos immunoreactivity than male rats

Methamphetamine (meth) dependence is often characterized by persistent and chronic relapse (i.e., return to drug use). Previous work suggests females may be at greater risk to relapse. In this study, we extended this limited evidence and identified sex-dependent neural substrates related to meth-triggered reinstatement. Male and female Sprague-Dawley rats were implanted with indwelling jugular catheters. Half of the rats were then trained to self-administer meth (0.05 mg/kg/inf); the other half self-administered saline during 21 daily sessions (2 h). Rats were then given 12 extinction sessions. Twenty-four hours after the last extinction session, rats received reinstatement testing. Half of the rats received a meth-prime (0.3 mg/kg, IP) injection and the remaining rats received a saline injection. This design resulted in 4 separate groups for each sex, allowing for careful investigation of brain regions related to meth-triggered reinstatement. Brains were harvested following the reinstatement session and c-Fos immunoreactivity was measured in multiple brain regions. Meth triggered reinstatement in both sexes and this effect was more robust in females compared to males. Significant sex differences were detected. Females showed greater c-Fos immunoreactivity in the cingulate cortex area 1, lateral orbitofrontal cortex, prelimbic cortex, caudate-putamen, nucleus accumbens core and shell, and central nucleus of the amygdala following meth-primed reinstatement.

Interactive effects of DRD2 rs6277 polymorphism, environment and sex on impulsivity in a population-representative study

Previous research has shown that dopaminergic dysregulation and early life stress interact to impact on aspects of impulse control. This study aimed to explore the potentially interactive effects of the rs6277 polymorphism of the dopamine D2 receptor gene (DRD2), stressful or supportive environment and sex on behavioural and self-reported measures of impulsivity, as well as alcohol use - a condition characterised by a deficit in impulse control. The sample consisted of the younger cohort (n = 583) of the longitudinal Estonian Children Personality, Behaviour and Health Study. The results showed that the CC homozygotes (suggested to have decreased striatal D2 receptor availability) who had experienced stressful life events (SLE) or maltreatment in the family prior to age 15 showed higher self-reported maladaptive impulsivity at age 15. The genotype-SLE interaction and further association with sex was also evident in the frequency of alcohol use at age 15. Lack of warmth in the family contributed to significantly higher levels of thoughtlessness and more frequent alcohol use in CC carriers at age 25, whereas family support was associated with lower thoughtlessness scores in CC males, which may suggest a protective effect of supportive family environment in this group. Together the findings suggest that DRD2 rs6277 polymorphism, in interaction with environmental factors experienced in childhood and youth may affect facets of impulsivity. Future work should aim to further clarify the sex and age-specific effects of stressful and supportive environment on the development of neuronal systems that are compromised in disorders characterised by deficits in impulse control.

Influence of ovarian hormones on value-based decision-making systems: Contribution to sexual dimorphisms in mental disorders

Women and men exhibit differences in behavior when making value-based decisions. Various hypotheses have been proposed to explain these findings, stressing differences in functional lateralization of the brain, functional activation, neurotransmitter involvement and more recently, sex hormones. While a significant interaction of neurotransmitter systems and sex hormones has been shown for both sexes, decision-making in women might be particularly affected by variations of ovarian hormones. In this review we have gathered information from animal and human studies on how ovarian hormones affect decision-making processes in females by interacting with neurotransmitter systems at functionally relevant brain locations and thus modify the computation of decision aspects. We also review previous findings on impaired decision-making in animals and clinical populations with substance use disorder and depression, emphasizing how little we know about the role of ovarian hormones in aberrant decision-making.

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.

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.

Sex differences in the human reward system: convergent behavioral, autonomic and neural evidence

Several studies have suggested that females and males differ in reward behaviors and their underlying neural circuitry. Whether human sex differences extend across neural and behavioral levels for both rewards and punishments remains unclear. We studied a community sample of 221 young women and men who performed a monetary incentive task known to engage the mesoaccumbal pathway and salience network. Both stimulus salience (behavioral relevance) and valence (win vs loss) varied during the task. In response to high- vs low-salience stimuli presented during the monetary incentive task, men showed greater subjective arousal ratings, behavioral accuracy and skin conductance responses (P < 0.006, Hedges' effect size g = 0.38 to 0.46). In a subsample studied with functional magnetic resonance imaging (n = 44), men exhibited greater responsiveness to stimulus salience in the nucleus accumbens, midbrain, anterior insula and dorsal anterior cingulate cortex (P < 0.02, g = 0.86 to 1.7). Behavioral, autonomic and neural sensitivity to the valence of stimuli did not differ by sex, indicating that responses to rewards vs punishments were similar in women and men. These results reveal novel and robust sex differences in reward- and punishment-related traits, behavior, autonomic activity and neural responses. These convergent results suggest a neurobehavioral basis for sexual dimorphism observed in the reward system, including reward-related disorders.

Sex-Dependent Wheel Running Effects on High Fat Diet Preference, Metabolic Outcomes, and Performance on the Barnes Maze in Rats

Excessive and prolonged intake of highly palatable, high fat (HF) foods contributes to the pathogenesis of obesity, metabolic syndrome, and cognitive impairment. Exercise can restore energy homeostasis and suppress HF diet preference in rats. However, it is unclear if exercise confers similar protection against the detrimental outcomes associated with a chronic HF diet preference and feeding in both sexes. We used our wheel running (WR) and two-diet choice (chow vs. HF) paradigm to investigate the efficacy of exercise in reversing HF diet-associated metabolic and cognitive dysregulation in rats, hypothesizing that beneficial effects of exercise would be more pronounced in males. All WR rats showed HF diet avoidance upon running initiation, and males, but not females, had a prolonged reduction in HF diet preference. Moreover, exercise only improved glucose tolerance and insulin profile in males. Compared to sedentary controls, all WR rats improved learning to escape on the Barnes maze. Only WR females increased errors made during subsequent reversal learning trials, indicating a sex-dependent effect of exercise on behavioral flexibility. Taken together, our results suggest that exercise is more effective at attenuating HF-associated metabolic deficits in males, and highlights the importance of developing sex-specific treatment interventions for obesity and cognitive dysfunction.

Cocaine-induced inheritable epigenetic marks may be altered by changing early postnatal fostering

Here, we explored the hypothesis that parental cocaine exposure could alter epigenetic machinery in their drug-naive offspring while early postnatal fostering may further modify the accompanied neurochemical and functional components. Variant drug-naive pups were produced from cocaine-exposed or unexposed C57BL/6 female mice that were matched with their male counterparts for mating. Within 3 days of birth, half of the pups were cross-fostered and nurtured by non-biological lactating dams. The pups were initially examined for locomotor activity and memory performance and subsequently for changes in DNA methylation in promoter regions of cAMP response element modulator (Crem) and Fosb in the prefrontal cortex at 48 days postnatum. The impact of postnatal fostering on these parameters was also investigated. Our results showed that cocaine exposure significantly decreased both Crem and Fosb methylation in the prefrontal cortex of progenitor mice, while similar patterns of methylation were replicated in the brains of drug-naive non-fostered offspring mice but reversed by postnatal fostering. Furthermore, offspring raised by cocaine-exposed dams were impaired in discriminative learning and exhibited memory decline, whereas locomotor activity remains unaltered in all groups of mice. Our data provide some evidence that indirect exposure to cocaine may cause marked epigenetic changes within the cortical networks of drug-naive descendants and that mediation by Crem/Fosb signalling in this brain region may be beneficial, while early postnatal fostering may further engineer molecular switching that may predispose the individual to future risky behaviours as well as accumulative potential to developing cognitive impairment later in life.

The Endocrine System and Alcohol Drinking in Females

Sexually dimorphic effects of alcohol exposure throughout life have been documented in clinical and preclinical studies. In the past, rates of alcohol use disorder (AUD) were higher in men than in women, but over the past 10 years, the difference between sexes in prevalence of AUD and binge drinking has narrowed. Recent evidence adds to historical data regarding the influence of sex steroids on alcohol drinking and the interaction with stress-related steroids. This review considers the contribution of the endocrine system to alcohol drinking in females, with a focus on the hypothalamic pituitary gonadal axis and the hypothalamic pituitary adrenal axis and their reciprocal interactions. Emphasis is given to preclinical studies that examined genomic and rapid membrane effects of estrogen, progesterone, glucocorticoids, and GABAergic neurosteroids for their effects on alcohol drinking and models of relapse. Pertinent comparisons to data in males highlight divergent effects of sex and stress steroids on alcohol drinking and emphasize the importance of considering sex in the development of novel pharmacotherapeutic targets for the treatment of AUD. For instance, pharmacological strategies targeting the corticotropin releasing factor and glucocorticoid receptor systems may be differentially effective in males and females, whereas strategies to enhance GABAergic neurosteroids may represent a biomarker of treatment efficacy in both sexes.

Response to nicotine following overnight smoking abstinence during short-term progesterone treatment in women

Preclinical and clinical literature suggest that sex hormones impact tobacco use behaviors in women. The goal of this double-blind crossover laboratory study was to examine the effect of oral exogenous progesterone (200 mg twice per day) versus placebo on nicotine response using measures of motor speed and cognitive function in women following overnight smoking abstinence. We hypothesized that increased progesterone would blunt the nicotine response whereby producing less change in motor speed and cognition in response to nicotine exposure. Female smokers, age 18-35, were randomized to participate in two 9-day crossover testing weeks. Participants completed a lab session following overnight abstinence where they were administered nicotine nasal spray and asked to complete measures of immediate memory (IMT), delayed memory (DMT), word recall (WR), and finger tapping speed (FT). After the first 9-day testing week, participants resumed smoking and returned the following month to complete the identical lab session in the crossover condition. Forty-seven women were included in this analysis (n = 47). We found no differences in the magnitude of response for IMT, DMT, and WR between conditions. For FT, women had a blunted response to nicotine during the placebo condition. When examining the association between hormone levels and relative performance, we found increases in DMT, WR, and FT but decreases in IMT during the progesterone condition. We observed differences between progesterone versus placebo in relative change in some measures of nicotine response following overnight abstinence. Future studies are needed to further characterize this response. (PsycInfo Database Record (c) 2020 APA, all rights reserved).

Oral Contraceptives and Cigarette Smoking: A Review of the Literature and Future Directions

INTRODUCTION

Evidence continues to mount indicating that endogenous sex hormones (eg, progesterone and estradiol) play a significant role in smoking-related outcomes. Although approximately one out of four premenopausal smokers use oral contraceptives (OCs), which significantly alter progesterone and estradiol levels, relatively little is known about how OCs may influence smoking-related outcomes. Thus, the goal of this review article is to describe the state of the literature and offer recommendations for future directions.

METHODS

In March 2017, we searched seven databases, with a restriction to articles written in English, using the following keywords: nicotine, smoker(s), smoking, tobacco, cigarettes, abstinence, withdrawal, and craving(s). We did not restrict on the publication date, type, or study design.

RESULTS

A total of 13 studies were identified. Three studies indicated faster nicotine metabolism in OC users compared to nonusers. Five of six laboratory studies that examined physiological stress response noted heightened response in OC users compared to nonusers. Three studies examined cessation-related symptomatology (eg, craving) with mixed results. One cross-sectional study observed greater odds of current smoking among OC users, and no studies have explored the relationship between OC use and cessation outcomes.

CONCLUSIONS

Relatively few studies were identified on the role of OCs in smoking-related outcomes. Future work could explore the relationship between OC use and mood, stress, weight gain, and brain function/connectivity, as well as cessation outcomes. Understanding the role of OC use in these areas may lead to the development of novel smoking cessation interventions for premenopausal women.

IMPLICATIONS

This is the first review of the relationship between oral contraceptives (OCs) and smoking-related outcomes. The existing literature suggests that the use of OCs is related to increased nicotine metabolism and physiological stress response. However, the relationship between OC use and smoking-related symptoms (eg, craving) is mixed. Further, no published data were available on OC use and smoking cessation outcomes. Therefore, we recommend additional research be conducted to characterize the relationship between OC use and smoking cessation outcomes, perhaps as a function of the effect of OC use on mood, stress, weight gain, and brain function/connectivity.

Distinct relationships between risky decision making and cocaine self-administration under short- and long-access conditions

Substance use is strongly associated with impaired decision making, with cocaine use particularly linked to elevated risky and impulsive choice. It is not clear, however, whether such maladaptive decision making is a consequence of cocaine use or instead precedes and predisposes individuals to cocaine use. The current study was designed to specifically address the latter possibility with respect to risky choice in both male and female rats. Rats were first trained in a "Risky Decision-making Task" (RDT), in which they made discrete choices between a small, "safe" food reward and a large, "risky" food reward accompanied by increasing probabilities of mild footshock punishment. After reaching stable performance, rats underwent jugular catheter surgery followed by either short-access cocaine self-administration sessions (2 h, 0.5 mg/kg/infusion) for 5 days or long-access cocaine self-administration sessions (6 h, 0.5 mg/kg/infusion) for 14 days. Under short-access conditions, there was no relationship between risk preference and changes in cocaine intake over time, but greater risk aversion in females predicted greater overall cocaine intake. Under long-access conditions, heightened risk taking predicted greater escalation of cocaine intake over the course of self-administration, supporting the notion that pre-existing risk-taking behavior predicts cocaine intake. Collectively, results from these experiments have implications for understanding and identifying pre-existing vulnerabilities to substance use, which may lead to strategies to prevent development of substance use disorders.

N-acetylcysteine yields sex-specific efficacy for cue-induced reinstatement of nicotine seeking

Women report greater craving during certain phases of the menstrual cycle. As well, research indicates that pharmacotherapies for smoking may be less efficacious in women compared with men, which may be due to interactions with natural fluctuations in ovarian hormone levels. N-Acetylcysteine (NAC) is a glutamatergic compound that has shown some efficacy in treating substance use disorders and aids in the prevention of relapse. However, it is unclear whether NAC has sex-specific effectiveness for nicotine relapse treatment. Given that NAC has shown promise to reduce nicotine reinstatement in preclinical models using male rats, the exploration of potential sex differences in the efficacy of NAC is warranted. Using a rat model, we first investigated the ability of NAC treatment (100 mg/kg, ip) during nicotine withdrawal with extinction training to reduce cue-induced nicotine seeking in male and female rats. Next, we assessed whether NAC's effects were estrous cycle-dependent for female rats. Results show that following NAC treatment during extinction, reinstatement of nicotine seeking was significantly decreased in males but not females, indicating a sex-specific effect of NAC. Furthermore, for females, both vehicle- and NAC-treated groups significantly reinstated nicotine-seeking behavior compared with extinction, regardless of estrous cycle phase. These results suggest that NAC is inefficacious in reducing nicotine relapse in females regardless of estrous cycle phase at the dose evaluated here. These collective findings could have important clinical implications for use and efficacy of NAC as a pharmacotherapy for freely cycling women smokers.

Oral Monosodium Glutamate Differentially Affects Open-Field Behaviours, Behavioural Despair and Place Preference in Male and Female Mice

Background:

Monosodium glutamate (MSG) is a flavour enhancer which induces behavioural changes in animals. However the influence of sex on the behavioural response to MSG has not been investigated.

Objective:

The sex-differential effects of MSG on open-field behaviours, anxiety-related behaviour, behavioural despair, place-preference, and plasma/brain glutamate levels in adult mice were assessed.

Methods:

Mice were assigned to three groups (1-3), based on the models used to assess behaviours. Animals in group 1 were for the elevated-plus maze and tail-suspension paradigms, group 2 for the open-field and forced-swim paradigms, while mice in group 3 were for observation in the conditioned place preference paradigm. Mice in all groups were further assigned into five subgroups (10 males and 10 females), and administered vehicle (distilled water at 10 ml/kg) or one of four doses of MSG (20, 40, 80 and 160 mg/kg) daily for 6 weeks, following which they were exposed to the behavioural paradigms. At the end of the behavioural tests, the animals were sacrificed, and blood was taken for estimation of glutamate levels. The brains were also homogenised for estimation of glutamate levels.

Results:

MSG was associated with a reduction in locomotion in males and females (except at 160 mg/kg, male), an anxiolytic response in females, an anxiogenic response in males, and decreased behavioural despair in both sexes (females more responsive). Postconditioning MSG-associated place-preference was significantly higher in females. Plasma/ brain glutamate was not significantly different between sexes.

Conclusion:

Repeated MSG administration alters a range of behaviours in a sex-dependent manner in mice.

Menstrual Cycle in Women Who Co-use Marijuana and Tobacco

OBJECTIVE

Marijuana is the most commonly used illicit drug in the United States and co-use with tobacco is increasing. Preliminary studies have indicated that marijuana may suppress luteinizing hormone (LH) or shorten the luteal phase. Although the literature is mixed, these sex hormones may play a role in smoking cessation outcomes. This secondary subgroup analysis aims to explore the menstrual cycle of females who co-use marijuana and tobacco compared with females who only use tobacco in a sample of tobacco treatment-seeking individuals.

METHODS

Female participants, aged 18 to 50 years, who self-reported regular menstrual cycles and co-use of marijuana and tobacco were matched 1:3 by age to participants who only use tobacco. Length of the follicular and luteal phases was determined using First Response Urine LH tests. Wilcoxon 2-sample t tests were used to determine differences in phase lengths between groups.

RESULTS

Thirteen women who co-use marijuana and tobacco, and 39 women who only use tobacco were included in this analysis. Overall, participants were 37.3 ± 8.0 (SD) years of age, mostly Caucasian (67%), and smoked 12.6 ± 5.2 (SD) cigarettes per day. The luteal phase length among participants who co-use marijuana and tobacco (11.4 days ± 2.2 [SD]) was significantly shorter than among participants who only use tobacco (16.8 days ± 11.3 [SD]; P = 0.002). No differences were found in follicular phase length or menstrual cycle length.

CONCLUSIONS

These data suggest that females who co-use marijuana and tobacco may have a shortened luteal phase in comparison with females who only use tobacco. Further studies are needed to better understand how marijuana use may impact the menstrual cycle and affect smoking outcomes.

Commentary on Tosun et al. (2019): Dynamic changes in sex hormones and smoking cessation

There is growing evidence suggesting that exogenous progesterone may improve smoking cessation outcomes among women. We hypothesize that exogenous progesterone administration can result in stable progesterone levels, and that it is the absence of dynamic hormone change that may lead to improved smoking cessation outcomes.

Exogenous progesterone for smoking cessation in men and women: a pilot double-blind, placebo-controlled randomized clinical trial

BACKGROUND AND AIMS

In some clinical studies men and women have been found to differ in their ability to quit smoking, perhaps as a result of progesterone. The primary aim of this study was to provide a preliminary test of whether progesterone (PRO), compared with placebo (PBO), was more effective for smoking cessation in men and women.

DESIGN

Pilot double-blind, placebo-controlled randomized clinical trial.

SETTING

Minneapolis/St Paul metro area, Minnesota, USA.

PARTICIPANTS

A total of 216 participants were randomized, including 113 men (18-60 years; PRO = 56, PBO = 57) and 103 women (18-50 years, pre-menopausal with self-reported regular menstrual cycles; PRO = 51, PBO = 52).

INTERVENTION

Participants were randomized (1 : 1 within sex group) to either PRO (200 mg twice daily) or PBO. Participants were assigned a quit date approximately 7 days after starting medication (luteal phase for women) and were followed for 12 weeks to assess relapse.

MEASUREMENTS

The primary outcome was self-reported 7-day point prevalence abstinence (PPA) at week 4. Secondary outcomes included 7-day PPA at weeks 8 and 12, prolonged abstinence, continuous abstinence, urine cotinine < 50 ng/ml, expired carbon monoxide ≤ 5 parts per million (p.p.m.) and days to relapse.

FINDINGS

There was a significant difference in 7-day PPA at week 4 among women [PRO: 18 (35.3%) versus PBO: 9 (17.3%), odds ratio (OR) = 2.61, 95% confidence interval (CI) = 1.04, 6.54, P = 0.041], but not among men [PRO: 13 (23.2%) versus PBO: 12 (21.1%), 1.13 (0.47, 2.76), P = 0.782]. There was some evidence that PRO delayed relapse in women (days to relapse; PRO: 20.5 ± 29.6 versus PBO: 14.3 ± 26.8, P = 0.03) but not in men (PRO: 13.4 ± 25.9 versus PBO: 13.3 ± 23.8, P = 0.69).

CONCLUSIONS

Oral micronized progesterone may aid smoking cessation in women.

Effects of early life stress on cocaine self-administration in post-pubertal male and female rhesus macaques

RATIONALE

Early life stress (ELS), including childhood maltreatment, is a predictive factor for the emergence of cocaine use disorders (CUDs) in adolescence.

OBJECTIVE

Accordingly, we examined whether post-pubertal male and female rhesus macaques that experienced infant maltreatment (maltreated, n = 7) showed greater vulnerability to cocaine self-administration in comparison with controls (controls, n = 7).

METHODS

Infant emotional reactivity was measured to assess differences in behavioral distress between maltreated and control animals as a result of early life caregiving. Animals were then surgically implanted with indwelling intravenous catheters and trained to self-administer cocaine (0.001-0.3 mg/kg/infusion) under fixed-ratio schedules of reinforcement. Days to acquisition, and sensitivity to (measured by the ED_Max dose of cocaine) and magnitude (measured by response rates) of the reinforcing effects of cocaine were examined in both groups.

RESULTS

Maltreated animals demonstrated significantly higher rates of distress (e.g., screams) in comparison with control animals. When given access to cocaine, control males required significantly more days to progress through terminal performance criteria compared with females and acquired cocaine self-administration slower than the other three experimental groups. The dose that resulted in peak response rates did not differ between groups or sex. Under 5-week, limited-access conditions, males from both groups had significantly higher rates of responding compared with females.

CONCLUSIONS

In control monkeys, these data support sex differences in cocaine self-administration, with females being more sensitive than males. These findings also suggest that ELS may confer enhanced sensitivity to the reinforcing effects of cocaine, especially in males.