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

Disrupting the endocannabinoid system in early adolescence negatively impacts sociability

Animal models suggest that the endocannabinoid system (eCS) helps regulate various aspects of social behavior, including play behavior and social reward, during adolescence. Properly tuned endocannabinoid signaling may be a critical developmental component in the emergence of normal adult sociability. In the current experiment, we attempted to pharmacologically disrupt endocannabinoid tone during early adolescence, and then measure the behavioral effects at two subsequent time points. 36 male and 36 female Long Evans rats received daily injections of one of three treatments between post-natal day (PND) 25-39: 1) vehicle treatment, 2) 0.4 mg/kg CP55,940 (a potent CB1/CB2 receptor agonist), or 3) 0.5 mg/kg AM251 (a CB1 receptor antagonist/inverse agonist). Both soon after treatment (PND 40-44) and several weeks later (PND 66-70), subjects were tested in an elevated plus maze (EPM) for anxiety and in a three-chambered apparatus for sociability. For the latter test, the number of entries into each chamber and the amount of time spent investigating each target were measured. Analyses revealed significant main effects of both sex and age on sociability: males expressed greater sociability compared to females, and sociability was higher in adolescence than adulthood. Most importantly, drug treatment (both CP55,940 and AM251) attenuated sociability in adolescence without having a significant effect on anxiety in the EPM. However, this effect did not persist into adulthood. These results indicate that pharmacological disruption of endocannabinoid tone - through either chronic agonism or antagonism of cannabinoid receptors - during early adolescence has a detrimental effect on sociability. This effect may be caused by transient, compensatory alterations in the eCS.

Effects of Cannabinoids on Female Sexual Function

INTRODUCTION

With the legalization of both medical and recreational marijuana in some countries and a few US states, its use has become more widely prevalent. Both exogenous cannabinoids such as tetrahydrocannabinol (THC) and endogenous cannabinoids (endocannabinoids) have been shown to affect female gonadotropin pathways and female sexuality. Yet, our understanding of the mechanisms and effects on female sexual function is limited.

AIM

To review the literature regarding the effects of both endogenous and exogenous cannabinoids on female sexual function in both animals and humans.

METHODS

We performed a PubMed search for English-language articles in peer-reviewed journals between 1970 and 2019. We used the following search terms: "cannabinoids," "endocannabinoids," "marijuana," "cannabis," and "female sexual function" or "sexual function." The main outcomes of the papers were reviewed.

MAIN OUTCOME MEASURE

The main outcome measure was sexual function in females.

RESULTS

A total of 12 human studies and 8 animal studies that evaluated the relationship between cannabinoids and female sexual function were included. Study types in animals were blinded, prospective, placebo-controlled trials. Human studies were based primarily on questionnaire data. The data indicate dose-dependent effects on female sexual desire and receptivity, such that low doses generally facilitate or have no effect but high doses inhibit.

CONCLUSIONS

More research is needed to develop a better understanding of the effects of cannabinoids on female sexual function. There does appear to be an effect on both animals and humans, but whether the effect is positive or negative along dose and species lines requires more study. With the legalization of marijuana occurring in more countries and more US states, there needs to be more well-controlled studies evaluating the effects. Lynn B, Gee A, Zhang L, et al. Effects of Cannabinoids on Female Sexual Function. Sex Med Rev 2020;8:18-27.

Broad and Region-Specific Impacts of the Synthetic Cannabinoid CP 55,940 in Adolescent and Adult Female Mouse Brains

Relative to Δ⁹-tetrahydrocannabinol (THC), the synthetic cannabinoid CP 55,940 (CP) is significantly more potent and efficacious at cannabinoid receptors, the primary targets for endogenous cannabinoids (eCBs). eCBs belong to a large, interconnected lipidome of bioactive signaling molecules with a myriad of effects in optimal and pathological function. Recreational use of highly potent and efficacious synthetic cannabinoids is common amongst adolescents, potentially impacting brain development. Knowledge of the molecular outcomes of synthetic cannabinoid use will be important to develop more targeted therapies for synthetic cannabinoid intoxication and to prevent long-term disruption to the CNS. Here, we test the hypothesis that CP has age and region-dependent effects on the brain lipidome. Adolescent [post-natal day (PND) 35 and PND 50] and young adult female mice were given either an acute dose of CP or vehicle and brains were collected 2 h later. Eight brain regions were dissected and levels of ∼80 lipids were screened from each region using HPLC/MS/MS. CP had widespread effects on the brain lipidome in all age groups. Interestingly, more changes were observed in the PND 35 mice and more were reductions in a lipid’s concentration, including region-dependent lowering of eCB levels. CP levels were highest in the cortex at PND 35, the hippocampus at PND 50, and in the cerebellum in the adult. These data provide novel insights into how high-potency, synthetic cannabinoids drive different, age-dependent, cellular signaling effects in the brain.

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

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

Endocannabinoid system in sexual motivational processes: Is it a novel therapeutic horizon?

The endocannabinoid system (ECS), which is composed of the cannabinoid receptors types 1 and 2 (CB1 and CB2) for marijuana's psychoactive ingredient Δ⁹-tetrahydrocannabinol (Δ⁹-THC), the endogenous ligands (AEA and 2-AG) and the enzymatic systems involved in their biosynthesis and degradation, recently emerged as important modulator of emotional and non-emotional behaviors. For centuries, in addition to its recreational actions, several contradictory claims regarding the effects of Cannabis use in sexual functioning and behavior (e.g. aphrodisiac vs anti-aphrodisiac) of both sexes have been accumulated. The identification of Δ⁹-THC and later on, the discovery of the ECS have opened a potential therapeutic target for sexual dysfunctions, given the partial efficacy of current pharmacological treatment. In agreement with the bidirectional modulation induced by cannabinoids on several behavioral responses, the endogenous cannabinoid AEA elicited biphasic effects on sexual behavior as well. The present article reviews current available knowledge on herbal, synthetic and endogenous cannabinoids with respect to the modulation of several aspects of sexuality in preclinical and human studies, highlighting their therapeutic potential.

The Impact of Exposure to Cannabinoids in Adolescence: Insights From Animal Models

The regular use of cannabis during adolescence is of particular concern because use by this age group seems to be associated with an increased likelihood of deleterious consequences, as reported by several epidemiologic studies. However, despite their unquestionable value, epidemiologic data are inconclusive. Modeling the adolescent phase in animals appears to be a useful approach to investigate the impact of cannabis use on the adolescent brain. In these models, adolescent cannabinoid exposure has been reported to cause long-term impairment in specific components of learning and memory and to have differential effects on anxiety, social behavior, and depressive-like signs. These findings suggest that it may represent, per se or in association with other hits, a risk factor for developing psychotic-like symptoms in adulthood. The neurobiological bases of this association include the induction of alterations in the maturational events of the endocannabinoid system occurring in the adolescent brain. Alterations in the endocannabinoid system may profoundly dysregulate developmental processes in some neurotransmitter systems, such as gamma-aminobutyric acid and glutamate, mainly in the cortex. The resulting picture strongly resembles the one present in schizophrenic patients, highlighting the translational value of this experimental approach.

The effects of adolescent cannabinoid exposure on seizure susceptibility and lethality in adult male rats

There is substantial evidence in rodent models that chronic exposure to cannabinoids during adolescence can alter the development of neurobiological systems that are implicated in regulating brain activity and seizure. The current study explored whether adolescent cannabinoid treatment affects subsequent, adult seizure susceptibility. Sixty male Wistar Kyoto rats were treated with either the synthetic cannabinoid, CP 55,940 (0.4mg/kg, one treatment per day), or vehicle between 35 and 45days old. Subjects were then allowed to mature to adulthood. At 68-69days of age, subjects were tested for seizure susceptibility using the pro-convulsant, pentylenetetrazol (PTZ). Subjects received an acute injection of either 35mg/kg or 50mg/kg PTZ immediately prior to a 30-min behavioral seizure test. PTZ doses were chosen to produce low-to-moderate levels of seizure activity in control subjects. There were no significant differences between treated and control subjects in: latency to first seizure, mean seizure severity, percentage who displayed any seizure activity, percentage who displayed clonic seizure, or percentage who displayed tonic-clonic seizure. However, CP 55,940-treated subjects had a higher mortality rate compared to controls at both PTZ doses, suggesting that adolescent cannabinoid exposure may increase the lethality of severe seizures experienced in adulthood.

Long-term consequences of perinatal and adolescent cannabinoid exposure on neural and psychological processes

Marihuana is the most widely consumed illicit drug, even among adolescents and pregnant women. Given the critical developmental processes that occur in the adolescent and fetal nervous system, marihuana consumption during these stages may have permanent consequences on several brain functions in later adult life. Here, we review what is currently known about the long-term consequences of perinatal and adolescent cannabinoid exposure. The most consistent findings point to long-term impairments in cognitive function that are associated with structural alterations and disturbed synaptic plasticity. In addition, several neurochemical modifications are also evident after prenatal or adolescent cannabinoid exposure, especially in the endocannabinoid, glutamatergic, dopaminergic and opioidergic systems. Important sexual dimorphisms are also evident in terms of the long-lasting effects of cannabinoid consumption during pregnancy and adolescence, and cannabinoids possibly have a protective effect in adolescents who have suffered traumatic life challenges, such as maternal separation or intense stress. Finally, we suggest some future research directions that may encourage further advances in this exciting field.

Sex-dependent vulnerability to cannabis abuse in adolescence

The goal of this review is to summarize current evidence for sex differences in the response to cannabinoid compounds, focusing mainly on a specific age of exposure, i.e., adolescence. Preclinical as well as clinical studies are examined. Among the different possible underlying mechanisms, the consistent dimorphism in the endocannabinoid system and delta9-tetrahydrocannabinol metabolism may play a part. All the collected data point to the need of including females in basic research as well as of analyzing results for sex differences in epidemiological studies.

Cannabis and adolescent brain development

Heavy cannabis use has been frequently associated with increased rates of mental illness and cognitive impairment, particularly amongst adolescent users. However, the neurobiological processes that underlie these associations are still not well understood. In this review, we discuss the findings of studies examining the acute and chronic effects of cannabis use on the brain, with a particular focus on the impact of commencing use during adolescence. Accumulating evidence from both animal and human studies suggests that regular heavy use during this period is associated with more severe and persistent negative outcomes than use during adulthood, suggesting that the adolescent brain may be particularly vulnerable to the effects of cannabis exposure. As the endocannabinoid system plays an important role in brain development, it is plausible that prolonged use during adolescence results in a disruption in the normative neuromaturational processes that occur during this period. We identify synaptic pruning and white matter development as two processes that may be adversely impacted by cannabis exposure during adolescence. Potentially, alterations in these processes may underlie the cognitive and emotional deficits that have been associated with regular use commencing during adolescence.

Susceptibility of the adolescent brain to cannabinoids: long-term hippocampal effects and relevance to schizophrenia

Clinical studies report associations between cannabis use during adolescence and later onset of schizophrenia. We examined the causal relationship between developmental cannabinoid administration and long-term behavioral and molecular alterations in mice. Mice were administered either WIN 55,212-2 (WIN), a cannabinoid receptor 1 (CB1) agonist or vehicle (Veh) during adolescence (postnatal day 30-35) or early adulthood (postnatal day 63-70). Behavioral testing was conducted after postnatal day 120 followed by biochemical assays. Adolescent cannabinoid treatment (ACU) leads to deficits in prepulse inhibition and fear conditioning in adulthood. Metabotropic glutamate receptors type 5 (mGluR5), a receptor critically involved in fear conditioning and endocannabinoid (eCB) signaling, is significantly reduced in the ACU mouse hippocampus. Next, we examined expression profiles of genes involved in eCB synthesis (diacylglycerol lipase (DGL)) and uptake (monoacylglycerol lipase (MGL) and fatty acid amide hydrolase (FAAH)) in the experimental mice. We find evidence of increased MGL and FAAH in ACU mice, reflecting increases in eCB uptake and degradation. These data suggest that administration of cannabinoids during adolescence leads to a behavioral phenotype associated with a rodent model of schizophrenia, as indexed by alterations in sensorimotor gating and hippocampal-dependent learning and memory deficits. Further, these deficits are associated with a reduction in hippocampal mGluR5 and a sustained change in eCB turnover, suggesting reduced eCB signaling in the ACU hippocampus. These data suggest that significant cannabis use during adolescence may be a contributory causal factor in the development of certain features of schizophrenia and may offer mGluR5 as a potential therapeutic target.