Male-female differences in the effects of cannabinoids on sexual behavior and gonadal hormone function

Depression symptoms associated with cannabis dependence in an adolescent American Indian community sample

BACKGROUND

Depression and substance use disorders, including cannabis dependence, arise during adolescence, are frequently comorbid, and represent major health burdens in the general US population. Yet little is known about the association of depression symptoms with cannabis and other substance use and use disorders in Native American adolescents.

OBJECTIVE

To investigate the comorbidity of cannabis use and depression symptoms in Native American adolescents.

METHODS

This study used the Children's Semi-Structured Assessment for the Genetics of Alcoholism (Adolescent Version) to obtain lifetime DSM-III-R diagnoses from a community sample of 202 (98 boys, 104 girls) American Indian adolescents living on contiguous reservations.

RESULTS

Thirteen percent of boys and 38% of girls had a lifetime DSM-III-R major depression disorder (MDD) independent of substance use. Fifteen percent of boys and 41% of girls had a major depression episode (MDE) either coincident with or independent of cannabis use. MDE and several individual depression symptoms were significantly associated with cannabis dependence in boys but not in girls. The median ages of onset of MDE were the same in the boys and girls who had experienced both depression and cannabis use.

CONCLUSIONS

These findings suggest that the association of depression with cannabis dependence is more significant in boys than girls in this population of adolescents.

SCIENTIFIC SIGNIFICANCE

Understanding comorbidity between depression and cannabis use is important in order to disentangle the etiological relationship between the two and also for designing more effective treatment and prevention strategies, particularly in Native Americans who are at high risk for both disorders.

Sex differences in cannabinoid pharmacology: a reflection of differences in the endocannabinoid system?

Marijuana is the most widely used illicit drug in the U.S., and marijuana use by women is on the rise. Women have been found to be more susceptible to the development of cannabinoid abuse and dependence, have more severe withdrawal symptoms, and are more likely to relapse than men. The majority of research in humans suggests that women are more likely to be affected by cannabinoids than men, with reports of enhanced and decreased performance on various tasks. In rodents, females are more sensitive than males to effects of cannabinoids on tests of antinociception, motor activity, and reinforcing efficacy. Studies on effects of cannabinoid exposure during adolescence in both humans and rodents suggest that female adolescents are more likely than male adolescents to be deleteriously affected by cannabinoids. Sex differences in response to cannabinoids appear to be due to activational and perhaps organizational effects of gonadal hormones, with estradiol identified as the hormone that contributes most to the sexually dimorphic effects of cannabinoids in adults. Many, but not all sexually dimorphic effects of exogenous cannabinoids can be attributed to a sexually dimorphic endocannabinoid system in rodents, although the same has not yet been established firmly for humans. A greater understanding of the mechanisms underlying sexually dimorphic effects of cannabinoids will facilitate development of sex-specific approaches to treat marijuana dependence and to use cannabinoid-based medications therapeutically.

The role of endocannabinoids in gonadal function and fertility along the evolutionary axis

Endocannabinoids are natural lipids able to bind to cannabinoid and vanilloid receptors. Their biological actions at the central and peripheral level are under the tight control of the proteins responsible for their synthesis, transport and degradation. In the last few years, several reports have pointed out these lipid mediators as critical signals, together with sex hormones and cytokines, in various aspects of animal and human reproduction. The identification of anandamide (AEA) and 2-arachidonoylglycerol (2-AG) in reproductive cells and tissues of invertebrates, vertebrates and mammals highlights the key role played by these endogenous compounds along the evolutionary axis. Here, we review the main actions of endocannabinoids on female and male reproductive events, and discuss the interplay between them, steroid hormones and cytokines in regulating fertility. In addition, we discuss the involvement of endocannabinoid signalling in ensuring a correct chromatin remodeling, and hence a good DNA quality, in sperm cells.

Effects of the cannabinoid antagonist SR 141716 on sexual and motor behaviour in receptive female rats

1. The aim of the present study was to investigate the effect of the cannabinoid antagonist/inverse agonist SR 141716 (SR) on the receptive behaviour and sexual motivation of female rats. 2. Partner preference, receptivity and proceptivity were evaluated in ovariectomized female rats primed with oestrogen and progesterone and administered SR (1 or 2.5 mg/kg, i.p.) 20 min prior to testing. 3. In the partner preference test, a reduced interest in both stimulus animals (a sexually active male and an ovariectomized hormone-primed female) was detected in rats treated with SR at both doses, but no effect on preference score was observed. In the receptivity test, pronounced reductions in lordosis quotient, lordosis rating and in the percentage of receptive females were found in SR-treated rats compared with control rats. Proceptive behaviours were not significantly affected by either dose of SR. 4. In addition, we explored the behavioural effects induced by SR in female rats using the open field test. Only at the higher dose (i.e. 2.5 mg/kg) did SR markedly increased grooming and scratching behaviour. 5. The results demonstrate the ability of SR to reduce female sexual receptivity, but not sexual motivation. The reduction does not seem strictly related to the motor alterations induced by the cannabinoid antagonist.

Monohydroxylated metabolites of the K2 synthetic cannabinoid JWH-073 retain intermediate to high cannabinoid 1 receptor (CB1R) affinity and exhibit neutral antagonist to partial agonist activity

K2 and several similar purported "incense products" spiked with synthetic cannabinoids are abused as cannabis substitutes. We hypothesized that metabolism of JWH-073, a prevalent cannabinoid found in K2, contributes to toxicity associated with K2 use. Competition receptor binding studies and G-protein activation assays, both performed by employing mouse brain homogenates, were used to determine the affinity and intrinsic activity, respectively, of potential monohydroxylated (M1, M3-M5) and monocarboxylated (M6) metabolites at cannabinoid 1 receptors (CB1Rs). Surprisingly, M1, M4 and M5 retain nanomolar affinity for CB1Rs, while M3 displays micromolar affinity and M6 does not bind to CB1Rs. JWH-073 displays equivalent efficacy to that of the CB1R full agonist CP-55,940, while M1, M3, and M5 act as CB1R partial agonists, and M4 shows little or no intrinsic activity. Further in vitro investigation by Schild analysis revealed that M4 acts as a competitive neutral CB1R antagonist (K(b)∼40nM). In agreement with in vitro studies, M4 also demonstrates CB1R antagonism in vivo by blunting cannabinoid-induced hypothermia in mice. Interestingly, M4 does not block agonist-mediated responses of other measures in the cannabinoid tetrad (e.g., locomotor suppression, catalepsy or analgesia). Finally, also as predicted by in vitro results, M1 exhibits agonist activity in vivo by inducing significant hypothermia and suppression of locomotor activity in mice. In conclusion, the present study indicates that further work examining the physiological effects of synthetic cannabinoid metabolism is warranted. Such a complex mix of metabolically produced CB1R ligands may contribute to the adverse effect profile of JWH-073-containing products.

Circulating endocannabinoid concentrations and sexual arousal in women

INTRODUCTION

Several lines of evidence point to the potential role of the endocannabinoid system in female sexual functioning. These include results from studies describing the subjective effects of exogenous cannabinoids on sexual functioning in humans and the observable effects of exogenous cannabinoids on sexual functioning in other species, as well as results from studies investigating the location of cannabinoid receptors in the brain and periphery, and the effects of cannabinoid receptor activation on neurotransmitters implicated in sexual functioning. While these lines of research suggest a role for the endocannabinoid system in female sexual functioning, no studies investigating the relationship between concentrations of endogenous cannabinoids (i.e., arachidonoylethanolamide [AEA] and 2-arachidonoylglycerol [2-AG]) and sexual functioning have been conducted in any species.

AIM

To measure circulating endocannabinoid concentrations in relation to subjective and physiological indices of sexual arousal in women (N = 21).

METHODS

Serum endocannabinoid (AEA and 2-AG) concentrations were measured immediately prior to, and immediately following, viewing of neutral (control) and erotic (experimental) film stimuli in a repeated measures design. Physiological sexual arousal was measured via vaginal photoplethysmography. Subjective sexual arousal was measured both continuously and noncontinuously. Pearson's correlations were used to investigate the relationships between endocannabinoid concentrations and sexual arousal.

MAIN OUTCOME MEASURES

Changes in AEA and 2-AG concentrations from pre- to post-film and in relation to physiological and subjective indices of sexual arousal.

RESULTS

Results revealed a significant relationship between endocannabinoid concentrations and female sexual arousal, whereby increases in both physiological and subjective indices of sexual arousal were significantly associated with decreases in AEA, and increases in subjective indices of sexual arousal were significantly associated with decreases in 2-AG.

CONCLUSIONS

These findings support the hypothesis that the endocannabinoid system is involved in female sexual functioning, with implications for furthering understanding of the biological mechanisms underlying female sexual functioning.

Putative role of endocannabinoid signaling in the etiology of depression and actions of antidepressants

In the last few years, there have been several advances in the determination of the role of the endocannabinoid system in the etiology of depression and the functional actions of antidepressant drugs. Specifically, a deficiency in endocannabinoid signaling is sufficient to produce a "depressive-like" phenotype at the preclinical level (including changes in rewarding, emotional and cognitive behavior and biological changes such as increased HPA axis activity, impaired stress adaptation, reduced neurogenesis and altered serotonin negative feedback), and capable of inducing symptoms of depression in humans at a clinical level. In line with these findings, clinical populations diagnosed with depression are found to have reduced levels of circulating endocannabinoids and preclinical models of depression reveal a deficit in central endocannabinoid signaling. Moreover, facilitation of endocannabinoid signaling is sufficient to produce all of the behavioral and biochemical effects of conventional antidepressant treatments. Further, many forms of antidepressant treatments significantly alter endocannabinoid signaling, and in some of these cases this recruitment of endocannabinoid signaling is involved in the neuroadaptive effects of these treatments. Ultimately, these data present a compelling picture of the putative role of the endocannabinoid system in the processes subserving both the development and treatment of depression.

Adolescent cannabinoid exposure attenuates adult female sexual motivation but does not alter adulthood CB1R expression or estrous cyclicity

Adolescence is a developmental period characterized by neuronal remodeling and the maturation of adult emotionality, reproductive behavior and social behavior. We examined whether chronic cannabinoid exposure in adolescent rats alters female sexual motivation, estrous cyclicity, sucrose preference, and CB(1)R expression in adulthood. Female rats were administered with the synthetic cannabinoid agonist, CP-55,940 (0.4 mg/kg, intraperitoneal), daily during adolescent development (PND 35-45). In a subset of subjects, socio-sexual motivation was investigated in adulthood (PND 75-86) using a runway apparatus. Estrous cyclicity was tracked in adulthood via vaginal cytology and a single-mount test. A two-bottle sucrose preference test was also conducted to determine whether predicted changes in socio-sexual motivation might be linked to alterations in hedonic processing. CB(1)R expression was examined in two separate subsets of subjects, one sacrificed following drug treatment (PND 46) and one before behavioral testing (PND 74). Drug treatment significantly decreased adult preference for a male conspecific (sexual motivation), as assessed by both Run Time and Proximity Time, but did not affect estrous cyclicity or sucrose preference. CP-55,940 treatment also induced immediate, but transient, decreases in CB(1)R expression in the ventromedial nucleus of the hypothalamus and amygdala. Drug treatment did not affect CB(1)R expression in the nucleus accumbens (core or shell) or globus pallidus at either time point. We suggest that the endocannabinoid system may play a role in the maturation of neuroendocrine axes and adult female reproductive behavior, and that chronic exposure to cannabinoids during adolescence disrupts these neurodevelopmental processes.

Marijuana use and testicular germ cell tumors

BACKGROUND

Since the early 1970s, the incidence of testicular germ cell tumors (TGCTs) in the United States has been increasing; however, potential environmental exposures accounting for this increase have not been identified. A previous study reported a significant association between frequent and long-term current marijuana users and TGCT risk. The purpose of this study was to evaluate the relation between marijuana use and TGCTs in a hospital-based case-control study.

METHODS

TGCT patients diagnosed between January 1990 and October 1996 (n = 187) and male friend controls (n = 148) were enrolled in the study. All participants were between the ages of 18 and 50 at the time of diagnosis and resided in Texas, Louisiana, Arkansas, or Oklahoma. Associations of marijuana use and TGCTs were estimated using unconditional logistic regression, adjusting for age, race, prior cryptorchidism, cigarette smoking, and alcohol intake.

RESULTS

Overall, patients with TGCTs were more likely to be frequent marijuana users (daily or greater) compared with controls (odds ratio [OR], 2.2; 95% confidence interval [CI], 1.0-5.1). Histological-specific analyses revealed that patients with nonseminoma were significantly more likely than controls to be frequent users (OR, 3.1; 95% CI, 1.2-8.2) and long-term (≥ 10 years) users (OR, 2.4; 95% CI, 1.0-6.1).

CONCLUSIONS

The finding of an association between frequent marijuana use and TGCTs, particularly among men with nonseminoma, was consistent with the findings of a previous report. Additional studies of marijuana use and TGCTs are warranted, especially studies evaluating the role of endocannabinoid signaling and cannabinoid receptors in TGCTs.

How important are sex differences in cannabinoid action?

In humans as in animals, males and females are dissimilar in their genetic and hormonally driven behaviour; they process information differently, perceive experience and emotions in different ways, display diverse attitudes, language and social skills, and show sex-related differences in the brain anatomy and organization. Drug addiction is a widespread relapsing illness that affects both men and women. Sex-dependent differences have been frequently observed in the biological and behavioural effects of substances of abuse, including cannabis. Beside sex differences observed in the cannabinoid-induced effects related to cannabis abuse and dependence, cannabinoids have been shown to exert sex-dependent effects also in other physiological and behavioural aspects, such as food intake and energy balance (more evident in males), or anxiety and depression (more evident in females). Research has just begun to identify factors which could provide a neurobiological basis for gender-based differences in cannabinoid effects, among which, gonadal hormones seem to play a crucial role. Yet, cannabinoid pharmacodynamic and pharmacokinetic may also be important, as sex differences in cannabinoid effects might be due, at least in part, to differences in muscle mass and fat tissue distribution between males and females. Here, we will review both clinical and laboratory-based research evidence revealing important sex-related differences in cannabinoid effects, and put forward some suggestions for future studies to fill the gap in our knowledge of gender-specific bias in cannabinoid pharmacology.

Estrogenic regulation of limbic cannabinoid receptor binding

Sex differences have been identified in many of the behavioral and physiological effects of cannabinoids. While estrogen has been linked to some of these variations, the effects of estrogen on cannabinoid receptor binding have not been characterized within regions of the brain specifically implicated in stress responsivity and emotional behavior. To examine sex differences, and the role of estradiol, in regulation of the cannabinoid receptor, we compared the binding site density of the cannabinoid receptor within the amygdala, hippocampus and hypothalamus in males, cycling females, ovariectomized (OVX) females and estradiol-treated OVX females (OVX+E). Our data reveal that males and OVX females have higher amounts of hypothalamic and lower amounts of amygdalar cannabinoid receptor binding relative to both cycling females and OVX+E females. Within the hippocampus, ovariectomy resulted in an upregulation of cannabinoid receptor binding. These data provide a putative biochemical mechanism mediating the observed behavioral and physiological sex differences in the effects of cannabinoids, particularly with respect to stress and emotional behavior.

Involvement of the endocannabinoid system in the neurobehavioural effects of stress and glucocorticoids

The endocannabinoid system is a neuroactive lipid signaling system that functions to gate synaptic transmitter release. Accumulating evidence has demonstrated that this system is responsive to modulation by both stress and glucocorticoids within the hypothalamus and limbic structures; however, the nature of this regulation is more complex than initially assumed. The aim of the current review is to summarize the research to date which examines the effects of acute stress and glucocorticoid administration on endocannabinoid signaling in limbic-hypothalamic-pituitary-adrenal (LHPA) axis, and in turn the role endocannabinoid signaling plays in the neurobehavioural responses to acute stress and glucocorticoid administration. The majority of research suggests that acute stress produces a mobilization of the endocannabinoid 2-arachidonoylglycerol (2-AG) while concurrently reducing the tissue content of the other endocannabinoid ligand anandamide. Genetic and pharmacological studies demonstrate that the reduction in anandamide signaling may be involved in the initiation of HPA axis activation and the generation of changes in emotional behaviour, while the increase in 2-AG signaling may be involved in terminating the stress response, limiting neuronal activation and contributing to changes in motivated behaviours. Collectively, these studies reveal a complex interplay between endocannabinoids and the HPA axis, and further identify endocannabinoid signaling as a critical regulator of the stress response.

The endocannabinoid system and nondrug rewarding behaviours

Rewarding behaviours such as sexual activity, eating, nursing, parenting, social interactions, and play activity are conserved strongly in evolution, and they are essential for development and survival. All of these behaviours are enjoyable and represent pleasant experiences with a high reward value. Remarkably, rewarding behaviours activate the same brain circuits that mediate the positive reinforcing effects of drugs of abuse and of other forms of addiction, such as gambling and food addiction. Given the involvement of the endocannabinoid system in a variety of physiological functions of the nervous system, it is not surprising that it takes part in the complex machinery that regulates gratification and perception of pleasure. In this review, we focus first on the role of the endocannabinoid system in the modulation of neural activity and synaptic functions in brain regions that are involved in natural and nonnatural rewards (namely, the ventral tegmental area, striatum, amygdala, and prefrontal cortex). Then, we examine the role of the endocannabinoid system in modulating behaviours that directly or indirectly activate these brain reward pathways. More specifically, current knowledge of the effects of the pharmacological manipulation of the endocannabinoid system on natural (eating, sexual behaviour, parenting, and social play) and pathological (gambling) rewarding behaviours is summarised and discussed.