Amphetamine pretreatment facilitates appetitive sexual behaviors in the female rat

Sexual effects of commonly used recreational psychostimulants in women and the female rat model

INTRODUCTION

Recreational psychostimulants have been associated with increased sexual activity or changes in sexual function in women, but every drug in this class has not shown consistent sexual effects in scientific studies. Further, some studies in female animal models may recapitulate the effects observed in humans, while others produce conflicting results. Overall, though, published studies on the sexual effects of recreational stimulants in women are lacking.

OBJECTIVES

The objective of this manuscript was to review the published sexual effects of prominent recreational psychostimulants in women and in the female rat model.

METHODS

Literature searches for "any years" were performed through PubMed and Google Scholar. Keywords for the searches included "amphetamine," "methamphetamine," "MDMA," "ecstasy," "3,4-methylenedioxymethamphetamine," "cocaine," "caffeine," "sex," "sexual," "female," and "women." Studies in humans and using animal models were included.

RESULTS

Older studies have shown that amphetamine produces a positive sexual effect in women, but often the sample size was too small to draw generalizable conclusions. Methamphetamine also has a positive effect on several sexual domains in women, as well as on vaginal lubrication. 3,4-Methylenedioxymethamphetamine may have a negative or positive effect on sexual activity, but often enhances the sensual aspects of sex. Though low doses of cocaine may heighten the sexual experience, most women who use cocaine experience negative sexual effects. Caffeine has been shown to enhance a physiological measure of arousal, vaginal blood flow, but based on our searches, no studies have investigated the subjective sexual effects of the drug.

CONCLUSION

Different recreational psychostimulants produce varying effects on sexual behavior and responses in women and female animal models, but more research is needed to understand these effects better.

Effects of cabergoline and dimethylcabergoline on the sexual behavior of male rats

RATIONALE

Cabergoline (CAB) is an ergot derivative typically prescribed for the treatment of hyperprolactinemia. It suppresses the release of prolactin through agonist actions on dopamine (DA) D2 receptors; however, it possesses binding affinity for other DA and 5-HT receptors. Side effects that exacerbate valvular heart disease can occur with high doses.

OBJECTIVE

The present study examined the acute, subchronic, and chronic dose-response effects of CAB and a derivative dimethylcabergoline (DMC) which acts as an antagonist instead of agonist at 5-HT 2B receptors, on appetitive and consummatory sexual behaviors of male rats.

METHODS

CAB (0, 0.03, 0.15, or 0.3 mg/kg/ml) was administered daily to sexually experienced male rats (N = 10/dose) by oral gavage for a total of 68 days. Sexual behavior was tested every 4 days during this period for a total of 16 trials. On the 17th trial, rats were administered their dose of CAB, and 4 h after were overdosed with sodium pentobarbital, perfused intracardially, and their brains processed for Fos immunohistochemistry. DMC (0, 0.03, 0.15, 0.3 mg/kg/ml) was administered daily to sexually experienced male rats (N = 10/dose) by oral gavage for a total of 36 days. Sexual behavior was tested every 4 days for a total of 9 trials.

RESULTS

CAB increased anticipatory level changes, intromissions, and ejaculations significantly across all timepoints, with the medium and high doses being most potent. The medium and high doses also increased Fos protein significantly within the medial preoptic area, whereas in the nucleus accumbens shell, the low and medium doses decreased Fos protein but the high dose increased it significantly from control. Similar to CAB, the medium and high doses of DMC increased the number of ejaculations significantly. Rats in all drug dose groups appeared healthy for the duration of the experiments.

CONCLUSIONS

Both CAB and DMC facilitate ejaculations, and CAB further facilitates measures of anticipatory sexual motivation and intromissions. These data suggest that both could be used as treatments for sexual arousal disorders and ejaculation/orgasm disorders with little or no untoward side effects at low doses.

Being friendly: paced mating for the study of physiological, behavioral, and neuroplastic changes induced by sexual behavior in females

Paced mating in rats is an experimental condition that allows the evaluation of sexual behavior in a way that closely resembles what occurs in seminatural and natural conditions enabling the female to control the rate of the sexual interaction. In conventional non-paced mating tests, females cannot escape from male approaches, which may lead to an unrewarding overstimulation. Paced mating is an alternative laboratory procedure that improves animal welfare and has a higher ethological relevance. The use of this procedure contributed to the identification of physiological and behavioral factors that favor reproduction. Paced mating includes motivational and behavioral components differentiating quantitative and qualitative characteristics that are critical for the induction of the rewarding properties of mating. These positive consequences ensure that the behavior will be repeated, favoring the species' survival. Sexual reward is an immediate consequence of paced mating, mediated mainly by the endogenous opioid system. Paced mating also induces long-lasting neuroplastic changes, including gene expression, synthesis of proteins, and neurogenesis in sex-relevant brain areas. The interest in paced mating is growing since the complexity of its elements and consequences at different levels in a laboratory setting resembles what occurs in natural conditions. In this review, we analyze the classic studies and recent publications demonstrating the advantages of using paced mating to evaluate different aspects of sexual behavior in females.

Experimentally altered male mating behaviour affects offspring exploratory behaviour via nongenetic paternal effects

Evidence is emerging that fathers can have nongenetic effects on the phenotypes of their offspring. Most studies have focused on the role that nongenetic modifications to sperm can have on offspring phenotype; however, fathers can also have nongenetic effects on offspring through their interactions with females, called female-mediated paternal effects. These effects can occur in situations where male phenotype, e.g. behaviour or morphology, affects female stress and/or provisioning of offspring. These effects are potentially widespread, but few studies have explicitly investigated the role of female-mediated paternal effects on offspring phenotype. Here, we asked if male mating interactions can affect offspring via female mediated paternal effects in the Trinidadian guppy, Poecilia reticulata. To do this, we manipulated mating behaviour by: (i) administering a drug known to affect the neurotransmitter dopamine, and (ii) varying the familiarity of potential mates, which affects attractiveness in this species. With these treatments, we successfully manipulated the mating behaviour of male guppies and female preference for those males. Further, we found significant effects of sire mating behaviour, sire drug treatment, and parental familiarity status on behavioural measures of offspring anxiety in response to a novel object. Because Control offspring of 'familiar' and 'unfamiliar' pairs differed in their behaviour, our results cannot be solely attributed to potential nongenetic modifications to sperm caused by the drug. These results emphasize the importance of female-mediated paternal effects, including those caused by altered male mating behaviour, in shaping offspring phenotype.

Wait and you shall see: sexual delay discounting in hypersexual Parkinson's disease

Patients with Parkinson's disease may develop impulse control disorders under dopaminergic treatments. Impulse control disorders include a wide spectrum of behaviours, such as hypersexuality, pathological gambling or compulsive shopping. Yet, the neural systems engaged in specific impulse control disorders remain poorly characterized. Here, using model-based functional MRI, we aimed to determine the brain systems involved during delay-discounting of erotic rewards in hypersexual patients with Parkinson's disease (PD+HS), patients with Parkinson's disease without hypersexuality (PD - HS) and controls. Patients with Parkinson's disease were evaluated ON and OFF levodopa (counterbalanced). Participants had to decide between two options: (i) wait for 1.5 s to briefly view an erotic image; or (ii) wait longer to see the erotic image for a longer period of time. At the time of decision-making, we investigated which brain regions were engaged with the subjective valuation of the delayed erotic reward. At the time of the rewarded outcome, we searched for the brain regions responding more robustly after waiting longer to view the erotic image. PD+HS patients showed reduced discounting of erotic delayed rewards, compared to both patients with Parkinson's disease and controls, suggesting that they accepted waiting longer to view erotic images for a longer period of time. Thus, when using erotic stimuli that motivate PD+HS, these patients were less impulsive for the immediate reward. At the brain system level, this effect was paralleled by the fact that PD+HS, as compared to controls and PD - HS, showed a negative correlation between subjective value of the delayed reward and activity of medial prefrontal cortex and ventral striatum. Consistent with the incentive salience hypothesis combining learned cue-reward associations with current relevant physiological state, dopaminergic treatment in PD+HS boosted excessive 'wanting' of rewards and heightened activity in the anterior medial prefrontal cortex and the posterior cingulate cortex, as reflected by higher correlation with subjective value of the option associated to the delayed reward when ON medication as compared to the OFF medication state. At the time of outcome, the anterior medial prefrontal/rostral anterior cingulate cortex showed an interaction between group (PD+HS versus PD - HS) and medication (ON versus OFF), suggesting that dopaminergic treatment boosted activity of this brain region in PD+HS when viewing erotic images after waiting for longer periods of time. Our findings point to reduced delay discounting of erotic rewards in PD+HS, both at the behavioural and brain system levels, and abnormal reinforcing effect of levodopa when PD+HS patients are confronted with erotic stimuli.10.1093/brain/awy298_video1awy298media15983845074001.

Repeated cocaine exposure dysregulates cognitive control over cue-evoked reward-seeking behavior during Pavlovian-to-instrumental transfer

Drug-paired cues acquire powerful motivational properties, but only lead to active drug-seeking behavior if they are potent enough to overwhelm the cognitive control processes that serve to suppress such urges. Studies using the Pavlovian-to-instrumental transfer (PIT) task have shown that rats pretreated with cocaine or amphetamine exhibit heightened levels of cue-motivated food-seeking behavior, suggesting that exposure to these drugs sensitizes the incentive motivational system. However, the PIT testing protocol can also create conflict between two competing behavioral responses to the reward-paired cue: active reward seeking (e.g., lever pressing) and passive conditioned food-cup approach behavior. We therefore investigated whether repeated cocaine exposure alters the way in which rats use cue-based reward expectations to resolve such conflict. In-depth analysis of previously published and new research confirmed that when drug-naïve rats are given a cue that signals the timing of a delayed noncontingent reward, they adaptively transition from reward seeking to conditioned approach behavior, facilitating efficient collection of the predicted reward. In contrast, cocaine-exposed rats exhibit pronounced behavioral dysregulation, increasing, rather than suppressing, their reward-seeking behavior over time, disrupting their ability to passively collect reward. Such findings speak to the important and sometimes overlooked role that cognitive control plays in determining the motivational impact of cues associated with drug and nondrug rewards.

Membrane estrogen receptor signaling impacts the reward circuitry of the female brain to influence motivated behaviors

Within the adult female, estrogen signaling is well-described as an integral component of the physiologically significant hypothalamic-pituitary-gonadal axis. In rodents, the timing of ovulation is intrinsically entwined with the display of sexual receptivity. For decades, the importance of estradiol activating intracellular estrogen receptors within the hypothalamus and midbrain/spinal cord lordosis circuits has been appreciated. These signaling pathways primarily account for the ability of the female to reproduce. Yet, often overlooked is that the desire to reproduce is also tightly regulated by estrogen receptor signaling. This lack of emphasis can be attributed to an absence of nuclear estrogen receptors in brain regions associated with reward, such as the nucleus accumbens, which are associated with motivated behaviors. This review outlines how membrane-localized estrogen receptors affect metabotropic glutamate receptor signaling within the rodent nucleus accumbens. In addition, we discuss how, as estrogens drive increased motivation for reproduction, they also produce the untoward side effect of heightening female vulnerability to drug addiction.

Does being drunk or high cause HIV sexual risk behavior? A systematic review of drug administration studies

HIV sexual risk behavior is broadly associated with substance use. Yet critical questions remain regarding the potential causal link between substance use (e.g., intoxication) and HIV sexual risk behavior. The present systematic review was designed to examine and synthesize the existing literature regarding the effects of substance administration on HIV sexual risk behavior. Randomized controlled experiments investigating substance administration and HIV sexual risk behavior (e.g., likelihood of condom use in a casual sex scenario) were included. Across five databases, 2750 titles/abstracts were examined and forty-three total peer reviewed published manuscripts qualified (few were multi-study manuscripts, and those details are outlined in the text). The majority of articles investigated the causal role of acute alcohol administration on HIV sexual risk behavior, although one article investigated the effects of acute THC administration, one the effects of acute cocaine administration, and two the effects of buspirone. The results of this review suggest a causal role in acute alcohol intoxication increasing HIV sexual risk decision-making. Although evidence is limited with other substances, cocaine administration also appears to increase sexual risk, while acute cannabis and buspirone maintenance may decrease sexual risk. In the case of alcohol intoxication, the pharmacological effects independently contribute to HIV sexual risk decision-making, and these effects are exacerbated by alcohol expectancies, increased arousal, and delay to condom availability. Comparisons across studies showed that cocaine led to greater self-reported sexual arousal than alcohol, potentially suggesting a different risk profile. HIV prevention measures should take these substance administration effects into account. Increasing the amount of freely and easily accessible condoms to the public may attenuate the influence of acute intoxication on HIV sexual risk decision-making.

Animal Models for the Study of Female Sexual Dysfunction

INTRODUCTION

Significant progress has been made in elucidating the physiological and pharmacological mechanisms of female sexual function through preclinical animal research. The continued development of animal models is vital for the understanding and treatment of the many diverse disorders that occur in women.

AIM

To provide an updated review of the experimental models evaluating female sexual function that may be useful for clinical translation.

METHODS

Review of English written, peer-reviewed literature, primarily from 2000 to 2012, that described studies on female sexual behavior related to motivation, arousal, physiological monitoring of genital function and urogenital pain.

MAIN OUTCOMES MEASURES

Analysis of supporting evidence for the suitability of the animal model to provide measurable indices related to desire, arousal, reward, orgasm, and pelvic pain.

RESULTS

The development of female animal models has provided important insights in the peripheral and central processes regulating sexual function. Behavioral models of sexual desire, motivation, and reward are well developed. Central arousal and orgasmic responses are less well understood, compared with the physiological changes associated with genital arousal. Models of nociception are useful for replicating symptoms and identifying the neurobiological pathways involved. While in some cases translation to women correlates with the findings in animals, the requirement of circulating hormones for sexual receptivity in rodents and the multifactorial nature of women's sexual function requires better designed studies and careful analysis. The current models have studied sexual dysfunction or pelvic pain in isolation; combining these aspects would help to elucidate interactions of the pathophysiology of pain and sexual dysfunction.

CONCLUSIONS

Basic research in animals has been vital for understanding the anatomy, neurobiology, and physiological mechanisms underlying sexual function and urogenital pain. These models are important for understanding the etiology of female sexual function and for future development of pharmacological treatments for sexual dysfunctions with or without pain. Marson L, Giamberardino MA, Costantini R, Czakanski P, and Wesselmann U. Animal models for the study of female sexual dysfunction. Sex Med Rev 2013;1:108-122.

Neural response to visual sexual cues in dopamine treatment-linked hypersexuality in Parkinson's disease

Hypersexuality with compulsive sexual behaviour is a significant source of morbidity for patients with Parkinson's disease receiving dopamine replacement therapies. We know relatively little about the pathophysiology of hypersexuality in Parkinson's disease, and it is unknown how visual sexual stimuli, similar to the portrayals of sexuality in the mainstream mass media may affect the brain and behaviour in such susceptible individuals. Here, we have studied a group of 12 patients with Parkinson's disease with hypersexuality using a functional magnetic resonance imaging block design exposing participants to both sexual, other reward-related and neutral visual cues. We hypothesized that exposure to visual sexual cues would trigger increased sexual desire in patients with Parkinson's disease with hypersexuality that would correspond to changes in brain activity in regions linked to dopaminergically stimulated sexual motivation. Patients with Parkinson's disease with hypersexuality were scanned ON and OFF dopamine drugs, and their results were compared with a group of 12 Parkinson's disease control patients without hypersexuality or other impulse control disorders. Exposure to sexual cues significantly increased sexual desire and hedonic responses in the Parkinson's disease hypersexuality group compared with the Parkinson's disease control patients. These behavioural changes corresponded to significant blood oxygen level-dependent signal changes in regions within limbic, paralimbic, temporal, occipital, somatosensory and prefrontal cortices that correspond to emotional, cognitive, autonomic, visual and motivational processes. The functional imaging data showed that the hypersexuality patients' increased sexual desire correlated with enhanced activations in the ventral striatum, and cingulate and orbitofrontal cortices. When the patients with Parkinson's disease with hypersexuality were OFF medication, the functional imaging data showed decreases in activation during the presentation of sexual cues relative to rest. These deactivations were not observed when the patients were ON medication, suggesting that dopamine drugs may release inhibition within local neuronal circuits in the cerebral cortex that may contribute to compulsive sexual behaviour. The findings of this study have implications with respect to the potential influence of cue exposure via exposure to mass media in enhancing libido, which in this group of vulnerable patients can lead to devastating social consequences and occasionally, custodial sentences. Stimulation through exposure to sexual visual cues in patients with Parkinson's disease with hypersexuality provides a motivational impetus for seeking this reward behaviour through activations and deactivations of cerebral cortex.

The effects of amphetamine exposure on outcome-selective Pavlovian-instrumental transfer in rats

RATIONALE

Repeated exposure to psychostimulants alters behavioral responses to reward-related cues; however, the motivational underpinnings of this effect have not been fully characterized.

OBJECTIVES

The following study was designed to examine how amphetamine sensitization affects performance in rats on a series of Pavlovian and operant tasks that distinguish between general-incentive and outcome-selective forms of conditioned responses.

METHODS

Adult male rats underwent Pavlovian and instrumental training for food pellet rewards. Following training, rats were sensitized to D-amphetamine (2 mg/kg for 7 days). Rats were subsequently tested on an outcome-selective Pavlovian-instrumental transfer (PIT) task, an outcome-reinstatement task, and an outcome devaluation task. Additionally, in a separate experiment, PIT was assessed in amphetamine-sensitized and control rats using a Pavlovian backward-conditioned stimulus.

RESULTS

Repeated amphetamine exposure sensitized locomotor activity to acute amphetamine challenge. Amphetamine altered responses to CS presentations by increasing conditioned approach. During tests of PIT, amphetamine-treated rats showed no outcome-selectivity in their responding, responding to a CS whether or not it shared a common outcome with the instrumental response. No effect of amphetamine sensitization was observed on tests of outcome-selective reinstatement by outcome delivery or action selection based on outcome value. Amphetamine-sensitized rats showed impaired outcome-selective PIT to a backward CS but were unaltered in conditioned approach.

CONCLUSIONS

Amphetamine sensitization prevents outcome-selective responding during PIT, which is dissociable from amphetamine's effects on conditioned approach. These data suggest fundamental alterations in how stimuli motivate action in addiction.

Prefrontal cell firing in male rats during approach towards sexually receptive female: interactions with cocaine

The medial prefrontal cortex (mPFC) plays a role in anticipation of rewards and goal orientation, properties that are influenced by cocaine administration. Single-unit firing was measured in the mPFC of seven male rats during the expression of approach responses toward a sexually receptive female. Nose-poking in male rats was used as a measure of approach behavior during the following periods: a baseline, first exposure to a female, a second baseline 2 h later and a second exposure to female 10 min after cocaine (15 mg kg⁻¹ i.p.). Two types of excitatory responses were identified. First, a subset of cells (23%) showed increased firing activity during nose-poke behavior upon presentation of the female, but not before. Another subset of cells (12%) showed increased firing in the presence of the female only after cocaine was administered. The present results provide preliminary evidence for neurons in the mPFC that are involved in sexually motivated approach behavior and that are modulated by cocaine.

Evaluating the rewarding nature of social interactions in laboratory animals

Positive social interactions are essential for emotional well-being, healthy development, establishment and maintenance of adequate social structures and reproductive success of humans and animals. Here, we review the studies that have investigated whether forms of social interaction that occur in different phases of the lifespan of animals, i.e., maternal behavior, social play and sexual interaction are rewarding in rodents and non-human primates. We show that these three forms of social interaction can be used as incentive for place conditioning, lever pressing and maze learning, three setups that have been extensively used to study the rewarding properties of food and drugs of abuse and their neural underpinnings. The experience of positive social interactions during key developmental ages has profound and long-lasting effects on brain function and behavior in emotional, motivational and cognitive domains. For instance, pup interaction is more rewarding than cocaine for early postpartum dams and rats deprived of the opportunity to play during adolescence show social and cognitive impairments at adulthood. Furthermore, sexual behavior is only overtly rewarding when animals can control the rate at which the sexual interaction occurs. Last, we discuss how animal models contributed to our understanding of social reward mechanisms and its psychological components throughout development.

Increased BOLD activation to predator stressor in subiculum and midbrain of amphetamine-sensitized maternal rats

Amphetamine, which is known to cause sensitization, potentiates the hormonal and neurobiological signatures of stress and may also increase sensitivity to stress-inducing stimuli in limbic areas. Trimethylthiazoline (5μL TMT) is a chemical constituent of fox feces that evokes innate fear and activates the neuronal and hormonal signatures of stress in rats. We used blood oxygen level dependent (BOLD) MRI to test whether amphetamine sensitization (1mg/kg, i.p. ×3days) in female rats has a lasting effect on the neural response to a stress-evoking stimulus, the scent of a predator, during the postpartum period. The subiculum and dopamine-enriched midbrain VTA/SN of amphetamine-sensitized but not control mothers showed a greater BOLD signal response to predator odor than a control putrid scent. The greater responsiveness of these two brain regions following stimulant sensitization might impact neural processing in response to stressors in the maternal brain.

The role of mesocorticolimbic dopamine in regulating interactions between drugs of abuse and social behavior

The use of addictive drugs can have profound short- and long-term consequences on social behaviors. Similarly, social experiences and the presence or absence of social attachments during early development and throughout life can greatly influence drug intake and the susceptibility to drug abuse. The following review details this reciprocal interaction, focusing on common drugs of abuse (e.g., psychostimulants, opiates, alcohol and nicotine) and social behaviors (e.g., maternal, sexual, play, aggressive and bonding behaviors). The neural mechanisms underlying this interaction are discussed, with a particular emphasis on the involvement of the mesocorticolimbic dopamine system.

Mixing pleasures: review of the effects of drugs on sex behavior in humans and animal models

Drugs of abuse act on the brain circuits mediating motivation and reward associated with natural behaviors. There is ample evidence that drugs of abuse impact male and female sexual behavior. First, the current review discusses the effect of drugs of abuse on sexual motivation and performance in male and female humans. In particular, we discuss the effects of commonly abused drugs including psychostimulants, opiates, marijuana/THC, and alcohol. In general, drug use affects sexual motivation, arousal, and performance and is commonly associated with increased sexual risk behaviors. Second, studies on effects of systemic administration of drugs of abuse on sexual behavior in animals are reviewed. These studies analyze the effects on sexual performance and motivation but do not investigate the effects of drugs on risk-taking behavior, creating a disconnect between human and animal studies. For this reason, we discuss two studies that focus on the effects of alcohol and methamphetamine on inhibition of maladaptive sex-seeking behaviors in rodents. Third, this review discusses potential brain areas where drugs of abuse may be exerting their effect on sexual behavior with a focus on the mesolimbic system as the site of action. Finally, we discuss recent studies that have brought to light that sexual experience in turn can affect drug responsiveness, including a sensitized locomotor response to amphetamine in female and male rodents as well as enhanced drug reward in male rats.

Inhibitory and disinhibitory effects of psychomotor stimulants and depressants on the sexual behavior of male and female rats

Drugs of abuse comprise several pharmacological classes, including psychomotor stimulants, such as amphetamine and cocaine, and CNS depressants, such as morphine and alcohol. Few studies have examined the effects of those drugs systematically on human sexual behavior, although substantial clinical and epidemiological literatures suggest that drugs in both classes either inhibit sexual responding or can be "prosexual" in certain situations, thereby increasing the potential of risky sexual activity and the spread of sexually transmitted diseases. This paper reviews original data in rats showing that both classes of drug inhibit or disinhibit sexual behavior depending on the animal's baseline level of sexual responding, hormonal status, whether the drug is given acutely or chronically, and whether the animal has learned to inhibit sexual responding toward nonreceptive partners or in the presence of conditioned olfactory cues that predict sexual nonreward.

Neural mechanisms of reproduction in females as a predisposing factor for drug addiction

There is an increasing awareness that adolescent females differ from males in their response to drugs of abuse and consequently in their vulnerability to addiction. One possible component of this vulnerability to drug addiction is the neurobiological impact that reproductive physiology and behaviors have on the mesolimbic dopamine system, a key neural pathway mediating drug addiction. In this review, we examine animal models that address the impact of ovarian cyclicity, sexual affiliation, sexual behavior, and maternal care on the long-term plasticity of the mesolimbic dopamine system. The thesis is that this plasticity in synaptic neurotransmission stemming from an individual's normal life history contributes to the pathological impact of drugs of abuse on the neurobiology of this system. Hormones released during reproductive cycles have only transient effects on these dopamine systems, whereas reproductive behaviors produce a persistent sensitization of dopamine release and post-synaptic neuronal responsiveness. Puberty itself may not represent a neurobiological risk factor for drug abuse, but attendant behavioral experiences may have a negative impact on females engaging in drug use.