Gender differences in response to intranasal cocaine administration to humans

Overdose mortality rates for opioids and stimulant drugs are substantially higher in men than in women: state-level analysis

Drug overdoses from opioids and stimulants are a major cause of mortality in the United States. It is unclear if there are stable sex differences in overdose mortality for these drugs across states, whether these differ across the lifespan, and if so, whether they can be accounted for by different levels of drug misuse. This was a state-level analysis of epidemiological data on overdose mortality, across 10-year age bins (age range: 15-74), using the CDC WONDER platform for decedents in the United States in 2020-1. The outcome measure was rate of overdose death (per 100,000) for: synthetic opioids (e.g., fentanyl), heroin, psychostimulants with potential for misuse (e.g., methamphetamine), and cocaine. Multiple linear regressions controlled for ethnic-cultural background, household net worth, and sex-specific rate of misuse (from NSDUH, 2018-9). For all these drug categories, males had greater overall overdose mortality than females, after controlling for rates of drug misuse. The mean male/female sex ratio of mortality rate was relatively stable across jurisdictions: synthetic opioids (2.5 [95% CI, 2.4-7]), heroin, (2.9 [95% CI, 2.7-3.1], psychostimulants (2.4 [95% CI, 2.3-5]), and cocaine (2.8 [95% CI, 2.6-9]). With data stratified in 10-year age bins, the sex difference generally survived adjustment (especially in the 25-64 age range). Results indicate that males are significantly more vulnerable than females to overdose deaths caused by opioid and stimulant drugs, taking into account differing state-level environmental conditions and drug misuse levels. These results call for research into diverse biological, behavioral, and social factors that underlie sex differences in human vulnerability to drug overdose.

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.

Overdose mortality rates for opioids or stimulants are higher in males than females, controlling for rates of drug misuse: State-level data

Importance

Drug overdoses from opioids like fentanyl and heroin and stimulant drugs such as methamphetamine and cocaine are a major cause of mortality in the United States, with potential sex differences across the lifespan.

Objective

To determine overdose mortality for specific drug categories across the lifespan of males and females, using a nationally representative state-level sample.

Design

State-level analyses of nationally representative epidemiological data on overdose mortality for specific drug categories, across 10-year age bins (age range: 15-74).

Setting

Population-based study of Multiple Cause of Death 2020-2021 data from the Centers of Disease Control and Prevention (CDC WONDER platform).

Participants

Decedents in the United States in 2020-2021.

Main outcome measures

The main outcome measure was sex-specific rates of overdose death (per 100,000) for: synthetic opioids excluding methadone (ICD-10 code: T40.4; predominantly fentanyl), heroin (T40.1), psychostimulants with potential for misuse, excluding cocaine (T43.6, predominantly methamphetamine; labeled "psychostimulants" hereafter), and cocaine (T40.5). Multiple regression analyses were used to control for ethnic-cultural background, household net worth, and sex-specific rate of misuse of the relevant substances (from the National Survey on Drug Use and Health, 2018-2019).

Results

For each of the drug categories assessed, males had greater overall overdose mortality than females, after controlling for rates of drug misuse. The mean male/female sex ratio of mortality rate for the separate drug categories was relatively stable across jurisdictions: synthetic opioids (2.5 [95%CI, 2.4-2.7]), heroin, (2.9 [95%CI, 2.7-3.1], psychostimulants (2.4 [95%CI, 2.3-2.5]), and cocaine (2.8 [95%CI, 2.6-2.9]). With data stratified in 10-year age bins, the sex difference generally survived adjustment for state-level ethnic-cultural and economic variables, and for sex-specific misuse of each drug type (especially for bins in the 25-64 age range). For synthetic opioids, the sex difference survived adjustment across the lifespan (i.e., 10-year age bins ranging from 15-74), including adolescence, adulthood and late adulthood.

Conclusions and Relevance

The robustly greater overdose mortality in males versus females for synthetic opioids (predominantly fentanyl), heroin, and stimulant drugs including methamphetamine and cocaine indicate that males who misuse these drugs are significantly more vulnerable to overdose deaths. These results call for research into diverse biological, behavioral, and social factors that underlie sex differences in human vulnerability to drug overdose.

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

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

A mechanistic overview of approaches for the treatment of psychostimulant dependence

Psychostimulant use disorder is a major health issue around the world with enormous individual, family-related and societal consequences, yet there are no effective pharmacological treatments available. In this review, a target-based overview of pharmacological treatments toward psychostimulant addiction will be presented. We will go through therapeutic approaches targeting different aspects of psychostimulant addiction with focus on three major areas; 1) drugs targeting signalling, and metabolism of the dopamine system, 2) drugs targeting either AMPA receptors or metabotropic glutamate receptors of the glutamate system and 3) drugs targeting the severe side-effects of quitting long-term psychostimulant use. For each of these major modes of intervention, findings from pre-clinical studies in rodents to clinical trials in humans will be listed, and future perspectives of the different treatment strategies as well as their potential side-effects will be discussed. Pharmaceuticals modulating the dopamine system, such as antipsychotics, DAT-inhibitors, and disulfiram, have shown some promising results. Cognitive enhancers have been found to increase aspects of behavioural control, and drugs targeting the glutamate system such as modulators of metabotropic glutamate receptors and AMPA receptors have provided interesting changes in relapse behaviour. Furthermore, CRF-antagonists directed toward alleviating the symptoms of the withdrawal stage have been examined with interesting resulting changes in behaviour. There are promising results investigating therapeutics for psychostimulant addiction, but further preclinical work and additional human studies with a more stratified patient selection are needed to prove sufficient evidence of efficacy and tolerability.

Bidirectional influence of heroin and cocaine escalation in persons with dual opioid and cocaine dependence diagnoses

Persons with dual severe opioid and cocaine use disorders are at risk of considerable morbidity, and the bidirectional relationship of escalation of mu-opioid agonists and cocaine use is not well understood. The aim of this study was to examine the bidirectional relationship between escalation of heroin and cocaine use in volunteers dually diagnosed with opioid and cocaine dependence (OD + CD). Volunteers from New York with OD + CD (total n = 295; male = 182, female = 113; age ≥ 18 years) were interviewed with the Structured Clinical Interview for the DSM-IV Axis I Disorders and Kreek-McHugh-Schluger-Kellogg scales for dimensional measures of drug exposure, which also collect ages of 1st use and onset of heaviest use. Time of escalation was defined as age of onset of heaviest use minus age of 1st use in whole years. Times of escalation of heroin and cocaine were positively correlated in both men (Spearman r = .34, 95% confidence interval [CI: .17, .48], p < .0001) and women (Spearman r = .51, [.27, .50], p < .0001) volunteers. After we adjusted for demographic variables, a Cox regression showed that time of cocaine escalation was a predictor of time of heroin escalation (hazard ratio [HR] = 0.97, 95% CI [0.95, 0.99], p = .003). Another Cox regression showed that this relationship is bidirectional, because time of heroin escalation was also a predictor of time of cocaine escalation (HR = 0.98, [0.96-0.99], p = .016). In these adjusted models, gender was not a significant predictor of time of escalation of either heroin or cocaine. Therefore, escalation did not differ robustly by gender when adjusting for demographics and other major variables. Overall, rapid escalation of cocaine use was a predictor of rapid escalation of heroin use, and vice versa, in persons with dual severe opioid and cocaine use disorders. These findings suggest a shared vulnerability to rapid escalation of these 2 drugs in persons with dual severe opioid and cocaine use disorders. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

Sex differences in cocaine-associated memory: The interplay between CB1, mGluR5, and estradiol

We know surprisingly little about the sex differences in the neurobiology of cocaine addiction, except females are more susceptible to the rewarding effects of cocaine than their male counterparts. Only a handful of recent studies have examined the neurobiology of cocaine-induced conditioned place preference (CPP) memory among female rodents. We contribute to this emerging line of research by documenting sex differences in cocaine-associated memory and illustrating the underlying signaling pathways in five experiments. Rimonabant (Rim), a cannabinoid CB₁ antagonist and inverse agonist, exerted a facilitating effect for low-dose cocaine and an impairing effect for high-dose cocaine CPP memory in male mice, as in our previous study, but not in female mice. Nor did we observe the effect exist among CB₁ knockout male mice, which indicated that the CB₁ receptors played a mediating role. We also found that the metabotropic glutamate receptor 5 (mGluR5) was located in the same signaling pathway as CB₁ in male mice. To clarify the mechanisms behind the sex differences, we used ovariectomized (OVX) female mice with estradiol benzoate (EB) replacement. In the OVX female mice, we showed that Rim-alone and EB-alone, but not Rim-and-EB-combined, facilitated the low-dose cocaine CPP memory. Moreover, 4-hydroxytamoxifen (4-OHT), an estrogen receptor (ER) antagonist, blocked Rim's and EB's facilitating effect. Finally, 2-methyl-6-(phenylethynyl)pyridine (MPEP), an mGluR5 antagonist, partially blocked EB's facilitating effect. In sum, we identified sex-specific effects of Rim on cocaine-induced CPP memory and the respective signaling pathways: mGluR5-CB₁ for male mice and ER-mGluR5-CB₁ for female mice. These findings may have merits for the development of sex-specific treatment for cocaine addiction.

Sex-related differences in subjective, but not neural, cue-elicited craving response in heavy cannabis users

BACKGROUND

Studies indicate that female cannabis users progress through the milestones of cannabis use disorder (CUD) more quickly than male users, likely due to greater subjective craving response in women relative to men. While studies have reported sex-related differences in subjective craving, differences in neural response and the relative contributions of neural and behavioral response remain unclear.

METHODS

We examined sex-related differences in neural and behavioral response to cannabis cues and cannabis use measures in 112 heavy cannabis users (54 females). We used principal component analysis to determine the relative contributions of neural and behavioral response and cannabis use measures.

RESULTS

We found that principal component (PC) 1, which accounts for the most variance in the dataset, was correlated with neural response to cannabis cues with no differences between male and female users (p = 0.21). PC2, which accounts for the second-most variance, was correlated with subjective craving such that female users exhibited greater subjective craving relative to male users (p = 0.003). We also found that CUD symptoms correlated with both PC1 and PC2, corroborating the relationship between craving and CUD severity.

CONCLUSIONS

These results indicate that neural activity primarily underlies response to cannabis cues and that a complex relationship characterizes a convergent neural response and a divergent subjective craving response that differs between the sexes. Accounting for these differences will increase efficacy of treatments through personalized approaches.

Drug-induced stress responses and addiction risk and relapse

A number of studies have assessed the effects of psychoactive drugs on stress biology, the neuroadaptations resulting from chronic drug use on stress biology, and their effects on addiction risk and relapse. This review mainly covers human research on the acute effects of different drugs of abuse (i.e., nicotine, cannabis, psychostimulants, alcohol, and opioids) on the hypothalamic-pituitary-adrenal (HPA) axis and the autonomic nervous system (ANS) responses. We review the literature on acute peripheral stress responses in naïve or light recreational users and binge/heavy or chronic drug users. We also discuss evidence of alterations in tonic levels, or tolerance, in the latter relative to the former and associated changes in the phasic stress responses. We discuss the impact of the stress system tolerance in heavy users on their response to drug- and stress-related cue responses and craving as compared to control subjects. A summary is provided of the effects of glucocorticoid responses and their adaptations on brain striatal and prefrontal cortices involved in the regulation of drug seeking and relapse risk. Finally, we summarize important considerations, including individual difference factors such as gender, co-occurring drug use, early trauma and adversity and drug use history and variation in methodologies, that may further influence the effects of these drugs on stress biology.

Female rats exhibit less avoidance than male rats of a cocaine-, but not a morphine-paired, saccharin cue

Rats avoid intake of an otherwise palatable taste cue when paired with drugs of abuse (Grigson and Twining, 2002). In male rats, avoidance of drug-paired taste cues is associated with conditioned blunting of dopamine in the nucleus accumbens (Grigson and Hajnal, 2007), conditioned elevation in circulating corticosterone (Gomez et al., 2000), and greater avoidance of the drug-paired cue predicts greater drug-taking (Grigson and Twining, 2002). While female rats generally are more responsive to drug than male rats, in this self-administration model, female rats consume more of a cocaine-paired saccharin cue and take less drug than males (Cason and Grigson, 2013). What is not known, however, is whether the same is true when a saccharin cue predicts availability of an opiate, particularly when the amount of drug experienced is held constant via passive administration by the experimenter. Here, avoidance of a saccharin cue was evaluated following pairings with experimenter delivered cocaine or morphine in male and female rats. Results showed that males and females avoided intake of a taste cue when paired with experimenter administered morphine or cocaine, and individual differences emerged whereby some male and female rats exhibited greater avoidance of the drug-paired cue than others. Female rats did not drink more of the saccharin cue than males when paired with morphine in Experiment 1, however, they did drink more of the saccharin cue than male rats when paired with cocaine in Experiment 2. While no pattern with estrous cycle emerged, avoidance of the cocaine-paired cue, like avoidance of a morphine-paired cue (Gomez et al., 2000), was associated with a conditioned elevation in corticosterone in both male and female rats.

Sex differences in behavioral and PKA cascade responses to repeated cocaine administration

Previous studies have shown sex different patterns in behavioral responses to cocaine. Here, we used between-subject experiment design to study whether sex differences exist in the development of behavioral sensitization and tolerance to repeated cocaine, as well as the role of protein kinase A (PKA) signaling cascade in this process. Ambulatory and rearing responses were recorded in male and female rats after 1 to 14 days of administration of saline or cocaine (15 mg/kg; ip). Correspondent PKA-associated signaling in the nucleus accumbens (NAc) and caudate-putamen (CPu) was measured at each time point. Our results showed that females exhibited higher cocaine-induced behavioral responses and developed behavioral sensitization and tolerance faster than males. Whereas females developed behavioral sensitization to cocaine after 2 days and tolerance after 14 days, male rats developed sensitization after 5 days. In addition, cocaine induced a sexual dimorphic pattern in the progression of neuronal adaptations on the PKA cascade signaling in region (NAc vs. CPu) and time (days of cocaine administration)-dependent manners. In general, more PKA signaling cascade changes were found in the NAc of males on day 5 and in the CPu of females with repeated cocaine injection. In addition, in females, behavioral activities positively correlated with FosB levels in the NAc and CPu and negatively correlated with Cdk5 and p35 in the CPu, while no correlation was observed in males. Our studies suggest that repeated cocaine administration induced different patterns of behavioral and molecular responses in the PKA cascade in male and female rats.

Sex differences in cocaine conditioned place preference in C57BL/6J mice

Men and women respond differently to the subjective effects of cocaine and cocaine-associated cues, which has implications for the development and maintenance of cocaine addiction. Preclinical studies performed in rats, modeling various aspects of cocaine addiction, have largely validated these results, indicating that female rats may be more sensitive to the rewarding properties of cocaine. The molecular mechanisms leading to sex differences in cocaine reward have largely not been determined, although sex hormones are thought to play a role. The mouse is commonly used as a model organism to study the molecular and genetic factors that influence a variety of psychiatric disorders. In particular, the inbred C57BL/6 mouse strain is often used for behavioral studies related to substance abuse. To begin to understand the hormonal, molecular and genetic mechanisms that might affect cocaine reward, we directly compared male and female C57BL/6J mice in cocaine conditioned place preference (CPP), a test that examines the rewarding and cue-associated properties of drugs of abuse. We conditioned mice at three doses of cocaine and examined preference and extinction of preference. We found that the acquisition of cocaine CPP did not differ between male and female mice. However, extinction of cocaine CPP was delayed in male mice compared with females at the lowest dose of cocaine. We conclude that sex differences in cocaine CPP can be observed in C57BL/6J mice at very low doses of cocaine.

Digital holographic microscopy discriminates sex differences in medial prefrontal cortex GABA neurons following amphetamine sensitization

Sex differences have been noted in patterns of drug use and relapse, and in particular with amphetamine abuse, implicating estradiol in mediating female neurobehavioral responses. To investigate the interaction of estradiol with amphetamine-induced hyperactivity, we compared male, intact female (INTACT), ovariectomized (OVX) and ovariectomized estradiol-treated (OVX+EB) female rats receiving repeated amphetamine (AMPH) treatment. All rats received intermittent AMPH injections for three days, and baseline and post-injection locomotor activity as well as fine-motor movements were recorded. Upon completion of behavioral experiments, immunohistochemistry was performed to assess parvalbumin-immunoreactive (PV-IR) GABAergic neurons in the medial prefrontal cortex (mPFC). Results indicate that AMPH induced greater behavioral response during habituation among the INTACT animals, and post-injection hyperactivity was apparent on days 2 and 3, among INTACT and OVX+EB females. For INTACT animals, the hyperactivity was most pronounced when estrogen levels were high. Immunohistochemical analysis using digital holographic microscopy revealed INTACT and OVX+EB females had less expression and smaller somatic area of PV-IR neurons in the mPFC. These data provide evidence for rapid development of sex differences in response to AMPH that correlates with sexually dimorphic alterations in a subset of mPFC GABAergic neurons implicated in modulating forebrain dopamine projections.

Genders and the concurrent use of cocaine and alcohol: Pharmacological aspects

AIMS

Gender-related differences in the pharmacological effects of addictive drug are an emerging issue. This review examines gender differences in both pharmacokinetic and pharmacodynamic aspects of alcohol and cocaine intake since they cause complex pharmacological interactions, not least the formation of the active metabolite cocaethylene.

METHODS

The MEDLINE database was searched from 1990 to 2014 in order to find articles related to gender differences in alcohol, cocaine and cocaethylene pharmacokinetics and pharmacodynamics.

RESULTS

Besides the well known gender differences in alcohol pharmacokinetics, women appear more susceptible to alcohol-mediated brain damage and seem to suffer more than men the acute effects of alcohol on hepatic and gonadal hormones. No significant gender differences have been found in the pharmacokinetics of cocaine taken alone; yet, in women pharmacological sensitivity to the drug seems to vary in relation to menstrual cycle; moreover, progesterone attenuates subjective effects of cocaine in women. Higher ratings at a subjective measure of mental/physical well-being have been observed in women when given cocaine and alcohol, alone or in combination. Finally, among subjects dependent on both alcohol and cocaine, men only benefit from naltrexone, whereas women used more cocaine during the trial and were less compliant to therapy than men.

CONCLUSIONS

The observed subtle gender differences in the pharmacokinetics and pharmacodynamics of both alcohol and cocaine may have no subtle influence on the natural history of the co-abuse of the two drugs by women.

An evaluation of the pharmacokinetics of methylphenidate for the treatment of attention-deficit/ hyperactivity disorder

INTRODUCTION

Methylphenidate (MPH) plays a principal role in the multimodal treatment of attention-deficit/hyperactivity disorder (ADHD). Controlled studies have demonstrated an effective reduction in the core symptoms of the disorder following MPH therapy, although long-term studies also demonstrate that the therapeutic benefits dissipate in the absence of combined psychosocial interventions.

AREAS COVERED

This review article focuses on the pharmacological characteristics of MPH, examining its effects on brain metabolism and the neurotransmitter system. Neuropsychological and clinical effects of different immediate and extended release MPH formulations are discussed to aid clinicians in choosing the appropriate formulation. The drug's addictive potency and abuse potential is also discussed. Data came from a literature search of relevant studies performed using the PubMed database up to June 2013.

EXPERT OPINION

MPH is effective in the treatment of the core symptoms of ADHD. Considerable clinical expertise is required to identify an individually well-adapted dosage which will produce the optimal clinical effects with potential side effects minimized. Due to low adherence to medication, especially in adolescents, motivation to treatment and attentive clinical monitoring is mandatory, as is the consideration of risks of abuse or the presence of a comorbid addictive disorder.

Demographic and socioeconomic correlates of powder cocaine and crack use among high school seniors in the United States

OBJECTIVES

Rates of powder cocaine and crack use have fluctuated among adolescents over recent decades. Little attention has been paid to recent trends, particularly regarding differences between users of powder cocaine and crack-two forms of the substance that are commonly reported together as "cocaine" use, despite having different effects and rates of adverse outcomes.

METHODS

We examined data from nationally representative samples of high school seniors who participated in the Monitoring the Future study during years 2005-2011 (weighted N = 65 717).

RESULTS

Many demographic and socioeconomic variables were similarly correlated with lifetime use of powder cocaine and crack. Income of >$50/week from job increased the odds for use, and income of >$50/week from sources other than a job more than doubled the odds for use. High religiosity, high parent education, identifying as black, and residing with one or two parents reduced odds for use. Hispanic students were at higher odds for use of crack and females were at lower odds for using powder cocaine. Among cocaine users, residing with one or two parents lowered odds for using both forms, and more religious students and Hispanics were at higher odds for crack-only use.

CONCLUSIONS

Those interested in preventing initiation and adverse consequences of cocaine use should take into account the overlapping, yet different risk profiles of powder cocaine and crack users when developing programming. This is particularly important when considering differences in legal consequences for these pharmacologically similar forms of cocaine.

Effects of menstrual cycle phase on cocaine self-administration in rhesus macaques

Epidemiological findings suggest that men and women vary in their pattern of cocaine use resulting in differences in cocaine dependence and relapse rates. Preclinical laboratory studies have demonstrated that female rodents are indeed more sensitive to cocaine's reinforcing effects than males, with estrous cycle stage as a key determinant of this effect. The current study sought to extend these findings to normally cycling female rhesus macaques, a species that shares a nearly identical menstrual cycle to humans. Dose-dependent intravenous cocaine self-administration (0.0125, 0.0250, and 0.0500 mg/kg/infusion) using a progressive-ratio schedule of reinforcement was determined across the menstrual cycle. The menstrual cycle was divided into 5 discrete phases - menses, follicular, periovulatory, luteal, and late luteal phases - verified by the onset of menses and plasma levels of estradiol and progesterone. Dependent variables including number of infusions self-administered per session, progressive ratio breakpoint, and cocaine intake were analyzed according to cocaine dose and menstrual cycle phase. Analysis of plasma hormone levels verified phase-dependent fluctuations of estradiol and progesterone, with estrogen levels peaking during the periovulatory phase, and progesterone peaking during the luteal phase. Progressive ratio breakpoint, infusions self-administered, and cocaine intake did not consistently vary based on menstrual cycle phase. These findings demonstrate that under the current experimental parameters, the reinforcing effects of cocaine did not vary across the menstrual cycle in a systematic fashion in normally cycling rhesus macaques.

Dissociating behavioral, autonomic, and neuroendocrine effects of androgen steroids in animal models

Developments in behavioral assessment, autonomic and/or baseline reactivity, psychopharmacology, and genetics, have contributed significantly to the assessment of performance-enhancing drugs in animal models. Particular classes of steroid hormones: androgenic steroids are of interest. Anecdotally, the performance enhancing effects of androgens are attributed to anabolic events. However, there is a discrepancy between anecdotal evidence and investigative data. While some androgen steroids may promote muscle growth (myogenesis), effects of androgens on performance enhancement are not always seen. Indeed, some effects of androgens on performance may be attributable to their psychological and cardiovascular effects. As such, we consider androgen effects in terms of their behavioral, autonomic, and neuroendocrine components. Techniques are discussed in this chapter, some of which are well established, while others have been more recently developed to study androgen action. Androgens may be considered for their positive impact, negative consequence, or psychotropic properties. Thus, this review aims to elucidate some of the effects and/or mechanisms of androgens on behavioral, autonomic, and/or neuroendocrine assessment that may underlie their controversial performance enhancing effects.

Blunted accumbal dopamine response to cocaine following chronic social stress in female rats: exploring a link between depression and drug abuse

RATIONALE

Women have twice the risk as men to develop depression. Approximately, 24% of major depression disorder cases have comorbid disorders with substance abuse. Several central systems, including dopaminergic and serotonergic pathways, are thought to be involved in such comorbidity.

OBJECTIVES

The present study established a chronic social stress model in female rats, which produces some cardinal features of depressive-like symptoms. Further, we examined the effects of acute cocaine on dopamine (DA) and serotonin (5-HT) in the nucleus accumbens (NAc) using this model.

METHODS

Female Long-Evans rats confronted a nursing dam in its home cage for 30 min twice daily for 21 days. The non-stressed control group was handled daily throughout the experiment. During the 21 days of stress, behaviors during confrontations, weight, preference for saccharin, and estrous cycles were measured. Ten days after the last confrontation, the experimental rat was challenged with 10 mg/kg of cocaine, and levels of DA and 5-HT in the NAc were measured using in vivo microdialysis.

RESULTS

During the course of daily confrontations for 21 days, the experimental females significantly increased the duration of immobility, reduced weight gain and the preference for saccharin, and disrupted estrous cycles during the stress. Chronic social stress significantly attenuated cocaine-induced DA levels, and to some extent, attenuated a percent change of 5-HT compared to the non-stressed control group.

CONCLUSIONS

Chronic social defeat stress for 21 days induced physiological and behavioral depression-relevant deficits and blunted response of dopaminergic and to some extent, serotonergic neurons to cocaine challenge in females.

Corticotrophin releasing factor (CRF) induced reinstatement of cocaine seeking in male and female rats

Significant sex differences have been demonstrated in clinical and preclinical studies of cocaine addiction, with some of the most consistent differences noted in regard to the role of stress and craving. The current study examined stress-induced reinstatement of cocaine seeking in male and female rats in an animal model of relapse using corticotropin-releasing factor (CRF) administration. Both male and female rats demonstrated increased cocaine seeking in response to CRF. CRF-induced reinstatement was highly variable across both male and female rats, and further analysis revealed a subpopulation that was particularly sensitive to CRF (high responders). Female high responders displayed significantly increased responding to CRF compared to males. Individual differences in stress responsivity could thus contribute to the likelihood of relapse, with females showing greater heterogeneity to stress-induced relapse.

Enhancement of cue-induced reinstatement of cocaine-seeking in rats by yohimbine: sex differences and the role of the estrous cycle

RATIONALE

Previous studies have shown that female rats exhibit enhanced cocaine-seeking across several phases of the addiction cycle when compared to males. Drug-seeking in females is also estrous cycle dependent and inversely associated with plasma progesterone. Although sex and estrous cycle-dependent differences have been reported in the reinstatement of cocaine-seeking triggered by cocaine injections or drug-paired cues, it is not yet known what role the estrous cycle may have on stress-induced reinstatement, either alone or in combination with drug-paired cues.

OBJECTIVES

Here, we examined male and female rats for reinstatement of extinguished cocaine-seeking produced by cocaine-paired cues or the stress-activating drug, yohimbine.

METHODS

Male and female Sprague-Dawley rats self-administered intravenous cocaine (0.5 mg/kg/infusion) paired with a light + tone stimulus for 10-14 days. Lever responding was then allowed to extinguish, with subsequent reinstatement testing occurring 30 min following an injection of yohimbine (1.25 or 2.5 mg/kg, intraperitoneal) or vehicle either in the presence or absence of the conditioned stimulus.

RESULTS

While males and females showed similar cue- and yohimbine-induced reinstatement (3-4 times over "No Cue"-vehicle responding), combining these stimuli resulted in a robust enhancement in cocaine-seeking in both groups, with a greater increase in females (10-12 vs. 14-15 times over "No Cue"-vehicle responding for the males and females, respectively). When examined as a function of the estrous cycle, females in proestrus demonstrated higher levels of responding during yohimbine + cues reinstatement.

CONCLUSIONS

This cycle-dependent enhanced sensitivity to stress enhancement of cocaine-paired cues may generalize to greater relapse susceptibility under stressful conditions.

Hormonal regulation of delta opioid receptor immunoreactivity in interneurons and pyramidal cells in the rat hippocampus

Clinical and preclinical studies indicate that women and men differ in relapse vulnerability to drug-seeking behavior during abstinence periods. As relapse is frequently triggered by exposure of the recovered addict to objects previously associated with drug use and the formation of these associations requires memory systems engaged by the hippocampal formation (HF), studies exploring ovarian hormone modulation of hippocampal function are warranted. Previous studies revealed that ovarian steroids alter endogenous opioid peptide levels and trafficking of mu opioid receptors in the HF, suggesting cooperative interaction between opioids and estrogens in modulating hippocampal excitability. However, whether ovarian steroids affect the levels or trafficking of delta opioid receptors (DORs) in the HF is unknown. Here, hippocampal sections of adult male and normal cycling female Sprague-Dawley rats were processed for quantitative immunoperoxidase light microscopy and dual label fluorescence or immunoelectron microscopy using antisera directed against the DOR and neuropeptide Y (NPY). Consistent with previous studies in males, DOR-immunoreactivity (-ir) localized to select interneurons and principal cells in the female HF. In comparison to males, females, regardless of estrous cycle phase, show reduced DOR-ir in the granule cell layer of the dentate gyrus and proestrus (high estrogen) females, in particular, display reduced DOR-ir in the CA1 pyramidal cell layer. Ultrastructural analysis of DOR-labeled profiles in CA1 revealed that while females generally show fewer DORs in the distal apical dendrites of pyramidal cells, proestrus females, in particular, exhibit DOR internalization and trafficking towards the soma. Dual label studies revealed that DORs are found in NPY-labeled interneurons in the hilus, CA3, and CA1. While DOR colocalization frequency in NPY-labeled neuron somata was similar between animals in the hilus, proestrus females had fewer NPY-labeled neurons that co-labeled with DOR in stratum oriens of CA1 and CA3 when compared to males. Ultrastructural analysis of NPY-labeled axon terminals within stratum radiatum of CA1 revealed that NPY-labeled axon terminals contain DORs that are frequently found at or near the plasma membrane. As no differences were noted by sex or estrous cycle phase, DOR activation on NPY-labeled axon terminals would inhibit GABA release probability equally in males and females. Taken together, these findings suggest that ovarian steroids can impact hippocampal function through direct effects on DOR levels and trafficking in principal cells and broad indirect effects through reductions in DOR-ir in NPY-labeled interneurons, particularly in CA1.

Influence of sex on reinstatement of cocaine-conditioned place preference

To explore sex differences in reinstatement of conditioned place preference, we subjected intact male and female Long Evans rats to an extended conditioned place preference (CPP) paradigm, which included observations of acquisition, extinction, and reinstatement of a preference to cocaine-paired stimuli. In a series of experiments, separate groups of animals were given six 30-min pairings of one chamber with cocaine (3, 5, 10, 15, 20, 25mg/kg) and six of the other with saline on alternate days. Overall, there were no sex differences in acquisition of cocaine CPP at any of the six doses tested (p>0.05). All animals established cocaine CPP at each of the six doses tested during the acquisition test, with the exception of the group of females conditioned with 5mg/kg. Preferences for the cocaine-paired chamber were successfully extinguished for both males and females after an extinction-training period. CPP reinstatement was achieved by the groups of males and females given training and priming doses of 10, 15, 20, and 25mg/kg (p<0.05). Overall, our reinstatement data demonstrate that reinstatement of cocaine CPP is greater for female versus male animals. Females showed a greater magnitude of reinstatement of cocaine CPP when trained and primed with 15 and 25mg/kg as compared to males (p<0.05). Further, at the three highest doses tested (15, 20, and 25mg/kg), females showed a greater magnitude of CPP in the reinstatement phase of CPP compared to that of the initial acquisition phase (p<0.05). The reinstatement data for the males show that the 20mg/kg dose resulted in the highest levels of reinstatement preference for male rats. These results indicate that sex differences in reinstatement to conditioned behavior maybe due, in part, to females forming a stronger association for the salience of the drug and the environment in which it was administered.

Estradiol: a key biological substrate mediating the response to cocaine in female rats

A consistent finding in drug abuse research is that males and females show differences in their response to drugs of abuse. In women, increased plasma estradiol is associated with increased vulnerability to the psychostimulant and reinforcing effects of drugs of abuse. Our laboratory has focused on the role of estradiol in modulating the response to cocaine. We have seen that ovariectomy increases the locomotor response to a single cocaine injection, whereas estradiol exacerbates the locomotor response to repeated cocaine administration. Cocaine-induced sensitization of brain activity, as measured by fMRI, is also dependent on plasma estradiol. Moreover, we observed that although all ovariectomized rats show conditioned place preference to cocaine, it is more robust in ovariectomized rats with estradiol. Opioid receptors are enriched in brain regions associated with pleasure and reward. We find that in females, the effectiveness of kappa opioid agonists in decreasing the locomotor response to repeated cocaine varies with plasma estradiol. We also find that estradiol regulates the density of mu opioid receptors in brains areas associated with reward. These data hint that in females, estradiol modulates the behavioral effects of cocaine by regulating mu and kappa opioid signaling in mesocorticolimbic brain structures. Identifying the mechanisms that mediate differences in vulnerability to drugs of abuse may lead to effective therapeutic strategies for the treatment and prevention of addiction and relapse. We encourage health practitioners treating persons addicted to drugs to consider gender differences in response to particular pharmacotherapies, as well the sex steroid milieu of the patient.

Sensitization enhances acquisition of cocaine self-administration in female rats: estradiol further enhances cocaine intake after acquisition

Cocaine self-administration in rodents has been used widely as a preclinical model of cocaine use in humans. In laboratory animals, estradiol enhances behavioral sensitization to cocaine and the acquisition of cocaine self-administration in female rats. The rewarding effect of cocaine has been shown to be enhanced following behavioral sensitization in male rats. This experiment examined whether behavioral sensitization to cocaine would promote cocaine-taking behavior in female rats, and whether estradiol could further modulate cocaine-taking behavior in cocaine-sensitized rats. Ovariectomized female rats were pretreated with either cocaine or saline for 4 days per week for 3 weeks. Self-administration sessions started 2 weeks after the last dose of drug. Female Sprague-Dawley rats received either estradiol or oil 30 min prior to the start of each session and self-administration was carried out 5 days per week for 4 weeks. The dose of cocaine self-administered each week was as follows (in mg/kg/infusion): week 1, 0.1; week 2, 0.1; week 3, 0.15; and week 4, 0.4. The rats that received cocaine pretreatment took fewer days to acquire cocaine self-administration and took more cocaine than rats that received saline pretreatment. Estradiol enhanced cocaine intake during the last six self-administration sessions after acquisition but did not affect acquisition of self-administration at the lowest doses of cocaine used. In conclusion, cocaine sensitization promotes the acquisition of cocaine self-administration in female rats. Furthermore, prior cocaine experience is more powerful than estradiol at enhancing acquisition, while estradiol enhances intake of cocaine after acquisition of self-administration.

Does the response to cocaine differ as a function of sex or hormonal status in human and non-human primates?

Stimulant abuse continues to be a growing problem among women. Over the last 10-15 years, an increasing number of studies have focused on factors that may be implicated in stimulant abuse in women as compared to men, including the role of hormonal fluctuations across the menstrual cycle. Numerous preclinical studies have documented that female rodents are more sensitive than male rodents to the behavioral effects of stimulant administration and the hormone estradiol is involved in the enhanced response to stimulants observed in females. In contrast, fewer studies have been conducted in humans and non-human primates addressing the role of sex and gonadal hormones on the effects of cocaine. This review paper presents a recent update on data collected in our Human Cocaine Challenge Laboratory and our Non-human Primate Laboratory, including analysis of cocaine pharmacokinetics, sex differences, the menstrual cycle, and the role of progesterone in modulating the response to cocaine. Our studies indicate that there is minimal evidence that the response to intranasal cocaine varies across the menstrual cycle or between men and women. In contrast, the response to smoked cocaine is greater in the follicular phase than the luteal phase and differences between men and women generally only emerge when men are compared to women in the luteal phase. In terms of potential hormonal mechanisms for these differences, the hormone progesterone attenuates the subjective response to cocaine. With respect to cocaine self-administration, there are minimal changes across the menstrual cycle in both humans and non-human primates. Thus, there is converging evidence across a range of species that the behavioral effects of cocaine (1) differ between males and females, (2) differ in relation to hormonal fluctuations, (3) can be attenuated by progesterone (at least in females), and (4) do not appear to be related to differences in cocaine pharmacokinetics.

Cocaine withdrawal-induced anxiety in females: impact of circulating estrogen and potential use of delta-opioid receptor agonists for treatment

Sex differences in cocaine addiction warrants further research focused on examining the growing population of female cocaine addicts. As demonstrated in both clinical and preclinical research, females are more susceptible to drug relapse with anxiety being a contributing factor. In support of this, a recent clinical study from our laboratory highlights the importance of menstrual cycle phase and anxiety at treatment admission for cocaine addiction on treatment retention. In support of these trends in the clinical population, the purpose of the present study was to design an animal model to directly test the role of circulating hormone levels during cocaine withdrawal. To directly measure the influence of estrogen on anxiety-like behavior during early stages of withdrawal, both ovariectomized and intact female rodent models were employed. The elevated-plus maze and elevated-zero maze were used to assess anxiety-like behavior. Recent evidence in male rodents highlights a potential role for the delta opioid-receptor (DOR) system in the modulation of cocaine withdrawal-induced anxiety. In addition to the evaluation of hormonal effects, a potential anxiolytic specific for DOR was tested for its efficacy in females withdrawn from cocaine. Our results support the use of DOR agonists as a potential anxiolytic in females and highlight the importance of estrogen and other circulating hormones during all phases of cocaine addiction.

Attenuation of estradiol on the reduction of striatal dopamine by amphetamine in ovariectomized rats

Amphetamine (AMPH) is a highly addictive drug of abuse which exhibits toxicity to dopaminergic neurons in long-term abusers. Estrogen seems to show neuroprotection in dopamine (DA) deficit caused by AMPH. The present study was to investigate the effects of estradiol on the levels of striatal DA in ovariectomized (Ovx) rats treated with or without AMPH. Female rats were Ovx for 2 weeks before administration of AMPH (5 mg/kg/day, i.p.) with or without 17beta-estradiol benzoate (EB) (25 microg/kg/day, s.c.) for 7 days. The striatal tissues were collected, homogenized with DA mobile phase, and centrifuged. The concentrations of DA in the supernatants were detected by HPLC. The protein expressions of dopamine transporter (DAT), vesicular monoamine transporter 2 (VMAT-2), and tyrosine hydroxylase (TH) were analyzed by Western blotting. The results indicated that AMPH could attenuate DA level significantly in striatum (P < 0.01). Comparing to control groups, administration of either EB or EB plus AMPH increased DA level (P < 0.01). The protein expression of striatal DAT was significant greater (P < 0.01) in rats treated with AMPH plus EB than AMPH treated animals. These results suggest that the DA levels in striatum can be enhanced by EB via an increase of DAT expression following administration of AMPH.

Sex differences in basal and cocaine-induced alterations in PKA and CREB proteins in the nucleus accumbens

INTRODUCTION

Alterations in protein kinase (PKA) protein levels have been implicated in the regulation of responses to and development of cocaine addiction. However, the contribution of differences in PKA intracellular cascade to the known sex differences in responses to cocaine is not well understood. This study examined whether there are intrinsic or cocaine-induced alterations in PKA-mediated responses, such as phosphorylation of cyclic AMP response element binding protein, in male and female rats.

MATERIALS AND METHODS

To this end, protein levels of PKA and phosphorylated CREB (pCREB) in the caudate putamen (CPu) and nucleus accumbens (NAc) of male and female rats were measured basally or after acute (one 30-mg/kg intraperitoneal injection) or chronic (twice-daily 15-mg/kg injections for 14 days) cocaine administration. Behavioral responses to both cocaine administration paradigms were also studied.

RESULTS

Similar to previous findings, ambulatory, rearing, and stereotypic activities were higher in female rats after acute cocaine administration. Sex differences in cocaine-induced responses were also observed after chronic cocaine administration: While males developed a robust sensitization in ambulatory activities to cocaine, females developed tolerance in cocaine-induced rearing and stereotypic activities. In the basal group, females had significantly higher PKA protein levels in the NAc. Regardless of the cocaine administration paradigm, PKA protein levels in the NAc were higher overall in females than in males. Furthermore, after cocaine administration, while pCREB protein levels in male rats were induced for a longer amount of time than in female rats, the magnitude of change on pCREB levels were higher in female than male rats. However, in the CPu, no sex differences in PKA or pCREB protein levels were observed either in the basal group or after acute or chronic cocaine administration.

DISCUSSION

Taken together, these findings suggest that sex differences in basal and cocaine-induced alterations in the PKA signaling regulation in the NAc may contribute to sex differences in the psychomotor responses to cocaine.

Attenuation of cocaine-seeking by progesterone treatment in female rats

Clinical research suggests that gender differences exist in cocaine dependence. Similarly, preclinical studies have shown that female rats exhibit higher response rates during cocaine self-administration, early extinction, and cocaine-primed reinstatement of drug-seeking. These effects are also estrous cycle dependent and inversely related to plasma progesterone, in that proestrus females (high progesterone) exhibit less cocaine-seeking, while estrous females (low progesterone) show the greatest cocaine-seeking. Based on these findings, we hypothesized that progesterone would attenuate cocaine-seeking behavior in intact, freely cycling animals. The role of the estrous cycle on cocaine-seeking behavior during early (first acquisition day) versus late (last maintenance day) cocaine self-administration was also examined. Female, Sprague-Dawley rats self-administered cocaine (0.5 mg/kg/infusion, IV) along a FR1 schedule, followed by daily extinction sessions in the absence of cocaine reinforcement. Once responding was extinguished, rats received an injection of cocaine (10 mg/kg, IP) immediately prior to reinstatement testing. Progesterone (2 mg/kg, SC) or vehicle was administered 20 and 2h prior to the first day of extinction (early cocaine withdrawal) and the reinstatement trials. To determine estrous cycle phase, we assessed vaginal cytology prior to the first acquisition and last maintenance days of cocaine self-administration, the first day of extinction training, and each reinstatement test. During early and late cocaine self-administration, proestrus and estrous females exhibited the greatest levels of active lever responding, respectively. A significant increase in responding also occurred during cocaine-primed reinstatement for estrous versus nonestrous females, an effect that was selectively attenuated by progesterone. However, progesterone was not effective at reducing cocaine-primed reinstatement for females in other phases of the estrous cycle, nor was it effective at reducing cocaine-seeking during early withdrawal. Taken together, these results suggest that progesterone may be a useful therapeutic for preventing relapse in abstinent female cocaine users, especially when the likelihood of relapse is greatest.

Sex differences in drug addiction: a review of animal and human studies

Addiction research has historically neglected research on women, and most studies have been conducted on men only, with the concluding results generalized to the female population. The role of sex differences in vulnerability to drug abuse, their repercussions on prevention and treatment strategies all require detailed studies, as does the progression from recreational drug use to dependence. This review synthesizes evidence of gender differences in drug addiction, with particular emphasis on women's health and implications. We first reviewed behavioral studies showing sex differences in the preference for and self-administration of licit (i.e., alcohol and nicotine) and illicit (i.e., cocaine, amphetamine, heroin and cannabis) substances as revealed by animal models of addiction. Clinical studies demonstrating differences between men and women in craving, drug use, abstinence and relapse will then be examined. For both animal and human studies, the effects of hormones and estrous/menstrual cycle will be reviewed. Finally, neurobiological factors underlying gender differences in vulnerability to drug addiction (i.e., brain morphology and neurotransmission) and need for gender-specific detoxification treatments will be discussed.

Basal and cocaine-induced sex differences in the DARPP-32-mediated signaling pathway

RATIONALE

Behavioral and dopamine responses to cocaine are sexually dimorphic: Female rats exhibit higher levels of locomotor and reward-associated behaviors after cocaine administration and dopamine release than do males. Activation of the dopamine- and cAMP-regulated phosphoprotein of Mr 32 kDa (DARPP-32) intracellular cascade mediates responses to cocaine.

OBJECTIVE

To examine the possibility that acute cocaine administration alters the DARPP-32 cascade in a sexually dimorphic pattern.

MATERIALS AND METHODS

Male and female rats received either saline or cocaine (30 mg/kg). Protein levels of DARPP-32, phosphorylation of DARPP-32 at the Thr34 site (P-Thr34-DARPP-32), protein phosphatase 1 (PP-1), and protein phosphatase 2B (PP-2B) in nucleus accumbens were measured via Western blot analysis.

RESULTS

Females had higher protein levels of DARPP-32, P-Thr34-DARPP-32, calcineurin A (CaN-A; catalytic subunit of PP-2B), and calcineurin B (CaN-B; regulatory subunit of PP-2B) than males 5 min after saline treatment. In females, CaN-A protein levels were also higher at 15 min and PP-1 protein levels were higher 30 min after saline administration than males. In male rats, cocaine significantly increased CaN-A protein levels at 30 min and CaN-B protein levels at 15 min. In females, cocaine administration significantly decreased protein levels of DARPP-32, P-Thr34-DARPP-32, and CaN-A at 45 min but increased PP-1 protein levels at 30 min. Overall, males had higher activation of the DARPP-32 pathway after cocaine administration than did females.

CONCLUSION

These novel results show that basal and cocaine-induced sex differences in the DARPP-32/PP-1 cascade may be responsible for the sexual dimorphism in acute cocaine-induced behavioral responses.

Sex differences in drug-related stress-system changes: implications for treatment in substance-abusing women

Extensive research indicates that chronic substance abuse disrupts stress and reward systems of the brain. Gender variation within these stress-system alterations, including the impact of sex hormones on these changes, may influence sex-specific differences in both the development of, and recovery from, dependency. As such, gender variations in stress-system function may also provide a viable explanation for why women are markedly more vulnerable than men to the negative consequences of drug use. This article therefore initially reviews studies that have examined gender differences in emotional and biophysiological changes to the stress and reward system following the acute administration of drugs, including cocaine, alcohol, and nicotine. The article then reviews studies that have examined gender differences in response to various types of stress in both healthy and drug-abusing populations. Studies examining the impact of sex hormones on these gender-related responses are also reported. The implications of these sex-specific variations in stress and reward system function are discussed in terms of both comorbid psychopathology and treatment outcome.

Individual differences in initial low-dose cocaine-induced locomotor activity and locomotor sensitization in adult outbred female Sprague-Dawley rats

Sex and individual differences are important considerations when studying cocaine responsiveness. We have previously shown that male Sprague-Dawley (S-D) rats can be classified as low or high cocaine responders (LCRs or HCRs, respectively) based on their locomotor activity following a single dose of cocaine (10 mg/kg, i.p.). Further, this distinction was found to predict dopamine transporter function, cocaine-induced locomotor sensitization, cocaine conditioned place preference and motivation to self-administer cocaine. Here we investigated whether or not individual differences in cocaine-induced locomotor activity and locomotor sensitization exist in female S-D rats. Female rats exhibited a broad range of locomotor activation following either a 5 or 10 mg/kg cocaine injection, allowing for classification as LCRs or HCRs. When administered over 7 days, both doses induced locomotor sensitization in female LCRs/HCRs. However, the magnitude of effects produced by 5 mg/kg cocaine in female LCRs/HCRs was more comparable to that produced by 10 mg/kg in male LCRs/HCRs, both of which, interestingly, developed sensitization in this study. These findings suggest that female S-D rats, like male S-D rats, can be classified as LCRs/HCRs and highlight the importance of accounting for dose when studying sex and individual differences to the effects of cocaine.

Subjective responses and cardiovascular effects of self-administered cocaine in cocaine-abusing men and women

This study aimed to examine sex differences in cocaine self-administration and cocaine-induced subjective and cardiovascular measures. The research was based on secondary analysis of data collected in our human laboratory in which subjects self-administered cocaine infusions (8, 16 and 32 mg/70 kg) over a 2-hour period under a fixed ratio 1, 5 minute time out schedule in three test sessions. Subjects were 10 women and 21 men with a history of either cocaine abuse or dependence who were not currently seeking treatment. Women and men self-administered similar amounts of cocaine. None of the subjective effects measures showed a significant main effect of sex during the cocaine self-administration session. Significant interactions were observed for subjective ratings of 'high' (sex x time) and 'stimulated' (sex x time x dose), with women reporting lower ratings over time/doses than men. Relative to men, cocaine produced dose- and time-dependent increases in feelings of hunger (i.e., reduced appetite suppression) in women. Systolic and diastolic blood pressures showed different patterns of change in men and women, with women showing less robust cocaine-induced increases than men. Taken together, these findings suggest that women and men may differ in their subjective and cardiovascular responses to self-administered cocaine. Further research that prospectively controls for hormonal influences upon these measures is needed.

Sex differences in non-reinforced responding for cocaine

Prior studies report no sex differences in cocaine consumption during maintenance of self-administration. We find female rats show poorer lever discrimination during acquisition of self-administration. Now, we test whether female rats show greater non-reinforced or ineffective responding (presses during infusion and time-out periods as well as inactive lever presses) than male rats during maintenance of cocaine self-administration (.0625-1.0 mg/kg/infusion) in Experiment 1. Persistence of responding during extinction when saline-replaced cocaine was also examined. Whether response differences reflect sex differences in movements under a non-drug condition was tested in Experiment 2. Because cocaine may affect lever press rates differentially between sexes, we examined the effects of cocaine (.3-30 mg/kg; IP) on responding for food in Experiment 3. Cocaine consumption does not differ between female and male rats. However, females respond more during infusion and time-out periods and during extinction than males. There is no sex difference in movements and high cocaine doses decrease responding for food more in female vs. male rats. That females engage in more ineffective responding may represent heightened "craving" and cannot be explained by increased movements or cocaine-stimulated increases in lever pressing. In contrast, responding for cocaine in males appears driven by drug delivery.

Gender differences in zebrafish responses to cocaine withdrawal

The acute responses to cocaine and its withdrawal contribute to cocaine dependence and potentiate relapse, with gender being one of the genetic factors affecting the outcome. Here we report that in both male and female zebrafish (Danio rerio, AB strain), an initial low-dose cocaine treatment (1.5 muM, immersion) does not acutely change their behavior. The cocaine withdrawal, however, is associated with an anxiety-like state that develops earlier in female zebrafish but is more robust and persistent in males, and can be acutely attenuated by cocaine administration. This is not a result of gender differences in the expression of anxiety-like state, since behavioral responses to an anxiogenic drug, FG-7142, are similar in male and female zebrafish. The basal brain dopamine (DA) levels and the expression of dopamine transporter mRNA (zDAT) show no significant sexual dimorphism. Acute cocaine exposure does not significantly change DA or zDAT. Withdrawal from repeated cocaine administration results in an overall reduction in zDAT, as well as an increase in DA levels. Neither treatment leads to significant gender differences in brain DA or zDAT. The common and gender-specific effects of cocaine on zebrafish, a well-characterized model of vertebrate development and genetics, should help in understanding the mechanisms involved in the anxiety associated with cocaine withdrawal and provide new opportunities in search for therapeutic solutions.

Gonadal steroids mediate the opposite changes in cocaine-induced locomotion across adolescence in male and female rats

Evidence from both human studies and animal models indicates that cocaine elicits more behavioral stimulation in females than males. The present study sought to determine whether sex-specific responses to cocaine emerge during adolescence and to determine if gonadal steroid action during puberty affects adult responsiveness to cocaine. We administered cocaine using an escalating dose model in male and female rats at ages postnatal (PN) 28, 42, and 65 days. To assess the effects of pubertal gonadal steroid action, we compared the effects of binge cocaine administration on intact and prepubertally gonadectomized male and female rats in adulthood. Cocaine responses changed in opposite directions in males and females as they progressed through adolescence. At most doses, adolescent males were more responsive than adult males whereas adult females were more responsive than adolescent females. Ambulatory activity was age-dependent in males whereas non-ambulatory activity was age-dependent in females. Prepubertal gonadectomy increased behavioral responsiveness to the highest dose of cocaine in males whereas it decreased behavioral responsiveness to lower doses of cocaine in females. We conclude that sex differences in behavioral responses to cocaine arise during adolescence from a concurrent decrease in male responsiveness and increase in female responsiveness. Our results suggest that gonadal steroids exert lasting and opposing effects on the sensitivity of males and females to psychostimulants during development.

Mechanisms of acute cocaine toxicity

Patients with acute cocaine poisoning present with life-threatening symptoms involving several organ systems. While the effects of cocaine are myriad, they are the result of a limited number of cocaine-protein interactions, including monoamine transporters, neurotransmitter receptors and voltage-gated ion channels. These primary interactions trigger a cascade of events that ultimately produce the clinical effects. The purpose of this article is to review the primary interactions of cocaine and the effects that these interactions trigger. We also describe the progression of symptoms observed in cocaine poisoning as they relate to serum cocaine concentrations.

Altered levels of sex and stress steroid hormones assessed daily over a 28-day cycle in early abstinent cocaine-dependent females

RATIONALE

There is growing evidence of alterations in brain stress and reward circuits associated with cocaine dependence. Sex differences are also documented and sex steroid hormones have been linked to cocaine reinforcement.

OBJECTIVES

The current study therefore assessed daily fluctuations in stress and sex hormones in cocaine-dependent females compared with healthy females.

METHOD

Daily salivary samples of cortisol, progesterone, and estradiol were collected at waking across 28 days from 12 cocaine-dependent females receiving inpatient treatment and 10 healthy females. Participants also completed mood-rating scales each week corresponding to four phases of the menstrual cycle and cocaine craving was monitored in cocaine patients at each phase.

RESULTS

Cocaine-dependent females in their first month of abstinence demonstrated significantly higher levels of both cortisol and progesterone across the menstrual cycle and significantly lower estradiol/progesterone (E2/P) ratios compared to healthy controls. They also showed significantly increased negative mood compared with controls, but no variation in cocaine craving across the menstrual cycle.

CONCLUSIONS

Findings indicate altered stress and sex hormones suggestive of an overactive stress system during the first month of cocaine abstinence after chronic cocaine abuse. These increased levels of cortisol and progesterone could impact both abstinence-related symptoms such as negative mood and susceptibility to drug-seeking behavior in cocaine-dependent females.

Sex and menstrual cycle effects on progressive ratio measures of cocaine self-administration in cynomolgus monkeys

Fluctuations in ovarian steroid hormones across the menstrual/estrous cycle influence the abuse-related effects of acute cocaine administration in women and chronic cocaine self-administration in rodents, but there have been no comparable studies in non-human primates. The interactions among sex, menstrual cycle phase, and cocaine self-administration (0.0032, 0.01, and 0.032 mg/kg/injection (inj)) under a progressive ratio schedule were investigated in four female and two male cynomolgus monkeys. Females were given unrestricted access to cocaine across 54 menstrual cycles, and males were studied over 23 pseudo-cycles of 30 days duration. Ovulatory cycles were defined by luteal phase elevations in progesterone and 44 cycles were ovulatory. During ovulatory menstrual cycles, females reached significantly higher progressive ratio break points than males at all three unit doses of cocaine (P<0.001). During anovulatory cycles, females also reached significantly higher break points than males for 0.032 mg/kg/inj cocaine (P<0.01). Progressive ratio break points for cocaine (0.01 and 0.032 mg/kg/inj) did not vary significantly as a function of ovarian steroid hormone levels during the follicular and the luteal phase of ovulatory menstrual cycles, or during anovulatory cycles. Progressive ratio break points for 0.0032 mg/kg/inj cocaine were significantly higher during the follicular phase than during the late luteal phase (P<0.05-0.001). There were no systematic changes in progressive ratio break points in male pseudo-cycles. Significant cocaine dose-related sex differences were observed, but no consistent changes in cocaine self-administration as a function of menstrual cycle phase, or levels of estradiol and progesterone, were detected in female cynomolgus monkeys.

Similar discriminative-stimulus effects of D-amphetamine in women and men

The results of controlled non-human animal and human laboratory studies are mixed regarding whether women and men respond differently to stimulant drugs. In order to assess potential gender differences in the effects of D-amphetamine, we conducted a retrospective analysis of six studies conducted in our laboratory that used identical procedures and measures. Thirteen women and fourteen men learned to discriminate 15 mg oral D-amphetamine. After acquiring the discrimination (i.e., >or=80% correct responding on 4 consecutive sessions), the effects of a range of doses of D-amphetamine (0, 2.5, 5, 10, and 15 mg) alone and in combination with other drugs, were assessed. Only data from sessions in which D-amphetamine was administered alone were included in this analysis. D-amphetamine functioned as a discriminative stimulus and dose-dependently increased drug-appropriate responding. Women and men did not differ in their ability to discriminate D-amphetamine. Women and men differed on participant-ratings of high (women<men), nausea (women>men) and sluggish (women<men), women also experienced greater increases in diastolic pressure than men. Because the results of this study may have been confounded by the training procedures, future research should use other behavioral arrangements (e.g. drug self-administration) to determine if women and men respond differently to the effects of D-amphetamine.

Progestins influence motivation, reward, conditioning, stress, and/or response to drugs of abuse

Progesterone (pregn-4-ene-3,20-dione; P) and its metabolite 5alpha-pregnan-3alpha-ol-20-one (3alpha,5alpha-THP) are secreted by ovaries, adrenals, and glial cells. 3alpha,5alpha-THP in the midbrain ventral tegmental area mediates sexual receptivity of rodents through its actions at GABA(A), NMDA, and/or D(1) receptors. The extent to which 3alpha,5alpha-THP may influence anti-anxiety/anti-stress effects, conditioning and/or reward through these substrates and/or by altering hypothalamic pituitary adrenal axis function is discussed. Biosynthesis of 3alpha,5alpha-THP occurs in responses to mating and may underlie some of the rewarding aspects of sexual behavior. Recent findings from our laboratory which demonstrate that progestins can enhance approach to novel stimuli, conditioning, and reinforcement are reviewed. How progestins' effects on these processes may underlie response to drugs of abuse is considered and new findings which demonstrate interactions between progestins and cocaine are presented.

Gender and stimulus difference in cue-induced responses in abstinent heroin users

BACKGROUND

Environmental stimuli associated with drug taking have been known to elicit drug craving and increase the likelihood of relapse, and sex differences have been observed in the development of drug addiction and relapse to drug taking. Differential cue paradigms (drug-related imagery scripts and drug-related paraphernalia) have been used to investigate cue-induced drug craving. However, there is little research on the possible gender differences in responses to drug cues in heroin-dependent individuals. This study examined whether two different stimuli, drug-related imagery scripts and drug-related paraphernalia, produce similar or different patterns of cue reactivity in heroin-dependent men and women.

METHODS

In the laboratory sessions, 26 male and 23 female heroin-dependent subjects were exposed to script-guided imagery of heroin-related cue situations and to heroin-related paraphernalia (e.g., needles, syringes, spoons, cigarette filters, and aluminum foil). Heroin craving, subjective anxiety, emotion state ratings, and cardiovascular changes were assessed.

RESULTS

Significant increases in heroin craving were seen with drug-imagery scripts or drug paraphernalia but not with neutral-relaxing imagery or neutral-item handling. In addition, drug imagery and paraphernalia produced significant increases in subjective anxiety, negative emotions, systolic and diastolic blood pressure, and heart rate, as well as decreases in positive emotion. Paraphernalia exposure was somewhat more effective than imagery scripts in inducing heroin craving, primarily reflecting a lower response to imagery scripts among men. Most other dependent measures also differed by gender, and each gender difference occurred with imagery scripts only or with paraphernalia only.

CONCLUSIONS

The present results indicate that heroin-imagery scripts and heroin paraphernalia each induce heroin craving and emotional and cardiovascular changes, but that the changes show a complex pattern of gender differences that may need to be taken into account in future laboratory studies.