Estrogen recruits the endocannabinoid system to modulate emotionality

Sex-specific alterations in emotional behavior and neurotransmitter systems in LPA1 receptor-deficient mice

Lysophosphatidic acid (LPA) and the endocannabinoid system (ECS) are critical lipid signaling pathways involved in emotional regulation and behavior. Despite their interconnected roles and shared metabolic pathways, the specific contributions of LPA signaling through the LPA1 receptor to stress-related disorders remain poorly understood. This study investigates the effects of LPA1 receptor deficiency on emotional behavior and neurotransmitter-related gene expression, with a focus on sex-specific differences, using maLPA1-null mice of both sexes. We hypothesized LPA1 receptor loss disrupts the interplay between LPA and the endocannabinoid 2-arachidonoylglycerol (2-AG) signaling, resulting in distinct behavioral and molecular alterations. maLPA1-null mice exhibited increased anxiety-like behaviors and altered stress-coping responses compared to wild-type counterparts, with more pronounced effects observed in females. Female mice also displayed higher corticosterone levels, though no genotype-related differences were observed. Plasma analyses revealed elevated LPA levels in maLPA1-null mice, suggesting a compensatory mechanism, and reduced 2-AG levels, indicating impaired ECS signaling. Gene expression profiling in the amygdala and medial prefrontal cortex showed significant alterations in the gene expression of key components of LPA and 2-AG signaling pathways, as well as neuropeptide systems such as corticotropin-releasing hormone (CRH) and neuropeptide Y (NPY). Glutamatergic signaling components also exhibited sex-specific variations. These findings suggest that LPA1 receptor deficiency impacts behavioral response and disrupts sex-specific neurotransmitter signaling, emphasizing the importance of LPA-ECS crosstalk in emotional regulation. This study provides insights into the molecular mechanisms underlying stress-related disorders such as depression and anxiety, which may inform the development of sex-specific therapeutic approaches.

Impaired mnemonic pattern separation associated with PTSD symptoms paradoxically improves with regular cannabis use

Posttraumatic stress disorder (PTSD) is associated with poor hippocampal function and disrupted pattern recognition. Cannabis use is highly prevalent in individuals with PTSD, yet the impact on these cognitive functions is poorly understood. Participants (n = 111) with a range of PTSD symptoms with and without regular cannabis use completed the mnemonic similarity task. We hypothesized that regular use would be associated with alterations in pattern separation ability in individuals with PTSD symptoms. High PTSD symptoms were associated with reduced pattern separation performance in minimal users. Regular users with high PTSD symptoms showed greater pattern separation, but reduced pattern separation with low PTSD symptoms. These results suggest that regular cannabis use may disrupt pattern separation and similar hippocampal-dependent processes, while it may improve pattern separation in individuals with high PTSD symptoms. These cross-sectional results require longitudinal follow-up studies to evaluate the causal effects of regular cannabis use on cognitive function in PTSD.

Neuronal biomarkers as potential therapeutic targets for drug addiction related to sex differences in the brain: Opportunities for personalized treatment approaches

Biological sex disparities manifest at various stages of drug addiction, including craving, substance abuse, abstinence, and relapse. These discrepancies are underpinned by notable distinctions in neurobiological substrates, encompassing brain structures, functions, and neurotransmitter systems implicated in drug addiction. Neuronal biomarkers, such as neurotransmitters, signaling proteins, and genes may be associated with the diagnosis, prognosis, and treatment outcomes in both biological sexes afflicted by drug abuse. Sex differences in the neural reward system, mainly through dopaminergic transmission during drug abuse, can be attributed to modifications in neurotransmitter systems and signaling pathways. This results in distinct patterns of neural activation and responsiveness to addictive substances in males and females. Sex hormones, the estrus/menstrual cycle, and cerebral neurochemistry contribute to the progression of psychological and physiological dependence in both male and female individuals grappling with addiction. Moreover, the alteration of sex hormone balance and neurotransmitter release plays a pivotal role in substance use disorders, subsequently modulating cognitive functions pertinent to reward, including memory formation, decision-making, and locomotor activity. Comparative investigations reveal distinctions in brain region volume, gene expression, neuronal firing, and circuitry in substance use disorders affecting individuals of both biological sexes. This review examines prevalent substance use disorders to elucidate the impact of sex hormones as therapeutic biomarkers on the mesocorticolimbic neurotransmitter systems via diverse mechanisms within the addicted brain. We underscore the imperative necessity of considering these variations to gain a deeper comprehension of addiction mechanisms and potentially discern sex-specific neuronal biomarkers for tailored therapeutic interventions.

Anxiety Modulation by Cannabinoids-The Role of Stress Responses and Coping

Endocannabinoids were implicated in a variety of pathological conditions including anxiety and are considered promising new targets for anxiolytic drug development. The optimism concerning the potentials of this system for anxiolysis is probably justified. However, the complexity of the mechanisms affected by endocannabinoids, and discrepant findings obtained with various experimental approaches makes the interpretation of research results difficult. Here, we review the anxiety-related effects of the three main interventions used to study the endocannabinoid system: pharmacological agents active at endocannabinoid-binding sites present on both the cell membrane and in the cytoplasm, genetic manipulations targeting cannabinoid receptors, and function-enhancers represented by inhibitors of endocannabinoid degradation and transport. Binding-site ligands provide inconsistent findings probably because they activate a multitude of mechanisms concomitantly. More robust findings were obtained with genetic manipulations and particularly with function enhancers, which heighten ongoing endocannabinoid activation rather than affecting all mechanisms indiscriminately. The enhancement of ongoing activity appears to ameliorate stress-induced anxiety without consistent effects on anxiety in general. Limited evidence suggests that this effect is achieved by promoting active coping styles in critical situations. These findings suggest that the functional enhancement of endocannabinoid signaling is a promising drug development target for stress-related anxiety disorders.

FAAH rs324420 Polymorphism: Biological Pathways, Impact on Elite Athletic Performance and Insights for Sport Medicine

Gene variation linked to physiological functions is recognised to affect elite athletic performance by modulating training and competition-enabling behaviour. The fatty acid amide hydrolase (FAAH) has been investigated as a good candidate for drug targeting, and recently, its single-nucleotide polymorphism (SNP) rs324420 was reported to be associated with athletic performance. Given the implications, the biological pathways of this genetic polymorphism linked to elite athletic performance, considering sport type, psychological traits and sports injuries, need to be dissected. Thus, a narrative review of the literature concerning the biological mechanisms of this SNP was undertaken. In addition to its role in athletic performance, FAAH rs324420 is also involved in important mechanisms underlying human psychopathologies, including substance abuse and neural dysfunctions. However, cumulative evidence concerning the C385A variant is inconsistent. Therefore, validation studies considering homogeneous sports modalities are required to better define the role of this SNP in elite athletic performance and its impact on stress coping, pain regulation and inflammation control.

The association of circulating endocannabinoids with neuroimaging and blood biomarkers of neuro-injury

BACKGROUND

Preclinical studies highlight the importance of endogenous cannabinoids (endocannabinoids; eCBs) in neurodegeneration. Yet, prior observational studies focused on limited outcome measures and assessed only few eCB compounds while largely ignoring the complexity of the eCB system. We examined the associations of multiple circulating eCBs and eCB-like molecules with early markers of neurodegeneration and neuro-injury and tested for effect modification by sex.

METHODS

This exploratory cross-sectional study included a random sample of 237 dementia-free older participants from the Framingham Heart Study Offspring cohort who attended examination cycle 9 (2011-2014), were 65 years or older, and cognitively healthy. Forty-four eCB compounds were quantified in serum, via liquid chromatography high-resolution mass spectrometry. Linear regression models were used to examine the associations of eCB levels with brain MRI measures (i.e., total cerebral brain volume, gray matter volume, hippocampal volume, and white matter hyperintensities volume) and blood biomarkers of Alzheimer's disease and neuro-injury (i.e., total tau, neurofilament light, glial fibrillary acidic protein and Ubiquitin C-terminal hydrolase L1). All models were adjusted for potential confounders and effect modification by sex was examined.

RESULTS

Participants mean age was 73.3 ± 6.2 years, and 40% were men. After adjustment for potential confounders and correction for multiple comparisons, no statistically significant associations were observed between eCB levels and the study outcomes. However, we identified multiple sex-specific associations between eCB levels and the various study outcomes. For example, high linoleoyl ethanolamide (LEA) levels were related to decreased hippocampal volume among men and to increased hippocampal volume among women (β ± SE =  - 0.12 ± 0.06, p = 0.034 and β ± SE = 0.08 ± 0.04, p = 0.026, respectively).

CONCLUSIONS

Circulating eCBs may play a role in neuro-injury and may explain sex differences in susceptibility to accelerated brain aging. Particularly, our results highlight the possible involvement of eCBs from the N-acyl amino acids and fatty acid ethanolamide classes and suggest specific novel fatty acid compounds that may be implicated in brain aging. Furthermore, investigation of the eCBs contribution to neurodegenerative disease such as Alzheimer's disease in humans is warranted, especially with prospective study designs and among diverse populations, including premenopausal women.

Association of FAAH rs324420 (C385A) Polymorphism with High-Level Performance in Volleyball Players

Genetic variants are recognized to affect athletic performance, partially by modulating competition-facilitating behavior. In this study, the role of three genetic variants previously linked to athlete status was investigated among elite volleyball players. A total of 228 players (26.7 ± 8.1 years old) participating in the Portuguese championship and with multiple medalists in national and international competitions were evaluated in terms of anthropometrics, training regime, sports experience, and a history of sports lesions. SNP genotyping was conducted by means of TaqMan^® Allelic Discrimination Methodology. Volleyball players showed significantly different anthropometric indicators and training habits according to sex (p < 0.05). The A allele of the genetic variant Fatty Acid Amide Hydrolase (FAAH) rs324420 (C385A) was shown to be significantly associated with superior athletic achievements under a dominant genetic model (AA/AC vs. CC, odds ratio (OR) = 1.70; 95% Cl, 0.93-3.13; p = 0.026; p < 0.001 after Bootstrap), which was corroborated by a multivariable analysis (AA/AC vs. CC adjusted OR = 2.00; 95% Cl, 1.04-3.82; p = 0.037). Age and hand length were also found to be independently associated with high-level performance (p < 0.05). Our results confirm the role of FAAH in athletic performance. More investigation into this polymorphism's potential impact on stress coping, pain, and inflammation regulation in sport, particularly in the scope of lesions prevention and treatment, is required.

Molecular and cellular mechanisms underlying brain region-specific endocannabinoid system modulation by estradiol across the rodent estrus cycle

Neurological crosstalk between the endocannabinoid and estrogen systems has been a growing topic of discussion over the last decade. Although the main estrogenic ligand, estradiol (E2), influences endocannabinoid signaling in both male and female animals, the latter experiences significant and rhythmic fluctuations in E2 as well as other sex hormones. This is referred to as the menstrual cycle in women and the estrus cycle in rodents such as mice and rats. Consisting of 4 distinct hormone-driven phases, the rodent estrus cycle modulates both endocannabinoid and exogenous cannabinoid signaling resulting in unique behavioral outcomes based on the cycle phase. For example, cannabinoid receptor agonist-induced antinociception is greatest during proestrus and estrus, when circulating and brain levels of E2 are high, as compared to metestrus and diestrus when E2 concentrations are low. Pain processing occurs throughout the cerebral cortex and amygdala of the forebrain; periaqueductal grey of the midbrain; and medulla and spine of the hindbrain. As a result, past molecular investigations on these endocannabinoid-estrogen system interactions have focused on these specific brain regions. Here, we will bridge regional molecular trends with neurophysiological evidence of how plasma membrane estrogen receptor (ER) activation by E2 leads to postsynaptic endocannabinoid synthesis, retrograde signaling, and alterations in inhibitory neurotransmission. These signaling pathways depend on ER heterodimers, current knowledge of which will also be detailed in this review. Overall, the aim of this review article is to systematically summarize how the cannabinoid receptors and endocannabinoids change in expression and function in specific brain regions throughout the estrus cycle.

Sex differences and hormonal regulation of metabotropic glutamate receptor synaptic plasticity

Striking sex differences exist in presentation and incidence of several psychiatric disorders. For example, major depressive disorder is more prevalent in women than men, and women who develop alcohol use disorder progress through drinking milestones more rapidly than men. With regards to psychiatric treatment responses, women respond more favorably to selective serotonin reuptake inhibitors than men, whereas men have better outcomes when prescribed tricyclic antidepressants. Despite such well-documented biases in incidence, presentation, and treatment response, sex as a biological variable has long been neglected in preclinical and clinical research. An emerging family of druggable targets for psychiatric diseases, metabotropic glutamate (mGlu) receptors are G-protein coupled receptors broadly distributed throughout the central nervous system. mGlu receptors confer diverse neuromodulatory actions of glutamate at the levels of synaptic plasticity, neuronal excitability, and gene transcription. In this chapter, we summarize the current preclinical and clinical evidence for sex differences in mGlu receptor function. We first highlight basal sex differences in mGlu receptor expression and function and proceed to describe how gonadal hormones, notably estradiol, regulate mGlu receptor signaling. We then describe sex-specific mechanisms by which mGlu receptors differentially modulate synaptic plasticity and behavior in basal states and models relevant for disease. Finally, we discuss human research findings and highlight areas in need of further research. Taken together, this review emphasizes how mGlu receptor function and expression can differ across sex. Gaining a more complete understanding of how sex differences in mGlu receptor function contribute to psychiatric diseases will be critical in the development of novel therapeutics that are effective in all individuals.

Lifespan changes in cannabinoid 1 receptor mRNA expression in the female C57BL/6J mouse brain

Many brain functions that underlie behavior, cognition, and emotions vary with age, as does susceptibility to neuropsychological disorders. The expression of specific genes that are involved in these functions, such as the genes encoding for oxytocin, its receptors, and apolipoprotein D, varies with age across different brain regions. The cannabinoid 1 receptor (CB₁ R) is one of the most widely spread G-protein coupled receptors in the central nervous system and is increasingly recognized for its important contribution to various brain functions. Although changes in CB₁ R expression with age have been reported in the male mouse brain, they have not been well investigated in the female brain. Here, we used fluorescence in situ hybridization to target CB₁ R mRNA in the whole brains of female C57BL/6J mice aged 4, 6, 12, 52 (12 months) and 86 weeks (20 months), and quantified CB₁ R-positive cells in 36 brain regions across the whole brain. The results showed that CB₁ R-positive cells number changed with age. Specifically, CB₁ R expression increased with age in some subregions of the cortex, decreased with age in the lateral septal area, and reached its lowest level at 52 weeks in the thalamus, hypothalamus, and hindbrain subregions. Cluster analysis revealed that some brain regions shared similar temporal characteristics in CB₁ R-positive cell number across the lifespan. Our results provide evidence that investigation of the neural basis of age-related characteristics of female brain functions is not only warranted but required.

A survey of medical cannabis use during perimenopause and postmenopause

OBJECTIVE

Expanding access to legal cannabis has dovetailed with increased interest in medical cannabis (MC) use; however, there is a paucity of research examining MC use to alleviate menopause-related symptoms. This survey study assessed patterns of MC use in perimenopausal and postmenopausal individuals.

METHODS

Participants (perimenopausal, n = 131; postmenopausal, n = 127) completed assessments of menopause-related symptomatology and cannabis use, including modes of use, type of use, and menopause-related symptoms addressed by MC use.

RESULTS

Most participants reported current cannabis use (86.1%) and endorsed using MC for menopause-related symptoms (78.7%). The most common modes of use were smoking (84.3%) and edibles (78.3%), and the top menopause-related symptoms for MC use were sleep disturbance (67.4%) and mood/anxiety (46.1%). Relative to postmenopausal participants, perimenopausal participants reported significantly worse menopause-related symptomatology on the vasomotor and psychosocial subscales of the Menopause-Specific Quality of Life Questionnaire ( P s ≤ 0.04), including greater burden of anxiety ( P = 0.01) and hot flash ( P = 0.04) symptoms. In addition, perimenopausal participants reported higher incidence of depression ( P = 0.03) and anxiety diagnoses ( P < 0.01), as well as increased use of MC to treat menopause-related mood/anxiety symptoms relative to postmenopausal participants ( P = 0.01).

CONCLUSIONS

Results suggest that many individuals are currently using MC as an adjunctive treatment for menopause-related symptoms, particularly sleep disturbance and mood/anxiety. Future research should examine the impact of different MC use characteristics (e.g., cannabinoid profiles) on the efficacy of MC use for menopause-related symptoms. Increased severity and prevalence of mood and anxiety symptoms in perimenopausal participants suggest promising targets for clinical trials of cannabinoid-based therapies.

FAAH rs324420 Polymorphism Is Associated with Performance in Elite Rink-Hockey Players

Genetic factors are among the major contributors to athletic performance. Although more than 150 genetic variants have been correlated with elite athlete status, genetic foundations of competition-facilitating behavior influencing elite performances are still scarce. This is the first study designed to examine the distribution of genetic determinants in the athletic performance of elite rink-hockey players. A total of 116 of the world’s top best rink-hockey players (28.2 ± 8.7 years old; more than 50% are cumulatively from the best four world teams and the best five Portuguese teams), who participated at the elite level in the National Rink-Hockey Championship in Portugal, were evaluated in anthropometric indicators/measurements, training conditions, sport experience and sport injuries history. Seven genetic polymorphisms were analyzed. Polymorphism genotyping was performed using the TaqMan® Allelic Discrimination Methodology. Rink-hockey players demonstrated significantly different characteristics according to sex, namely anthropometrics, training habits, sports injuries and genetic variants, such as Vitamin D Receptor (VDR) rs731236 (p < 0.05). The Fatty Acid Amide Hydrolase (FAAH) rs324420 A allele was significantly associated with improved athletic performance (AA/AC vs. CC, OR = 2.80; 95% Cl, 1.23−6.35; p = 0.014; p = 0.008 after Bootstrap) and confirmed as an independent predictor among elite rink-hockey players (adjusted OR = 2.88; 95% Cl, 1.06−7.80; p = 0.038). Our results open an interesting link from FAAH-related biology to athletic performance.

Leitl K, Megan Gray J, N Petrie G, J.Tellez-Monnery K, N.Hill M. Sex and stressor modality influence acute stress-induced dynamic changes in corticolimbic endocannabinoid levels in adult Sprague Dawley rats

Research over the past few decades has established a role for the endocannabinoid system in contributing to the neural and endocrine responses to stress exposure. The two endocannabinoid ligands, anandamide (AEA) and 2-arachidonoyl glycerol (2-AG), both play roles in regulating the stress response and both exhibit dynamic changes in response to stress exposure. Most of this previous research, however, was conducted in male rodents. Given that, especially in rodents, the stress response is influenced by sex, an understanding of how these dynamic responses of endocannabinoids in response to stress is influenced by sex could provide insight into sex differences of the acute stress response. We exposed adult, Sprague Dawley rats to different commonly utilized acute stress modalities, specifically restraint, swim and foot shock stress. Thirty minutes following stress onset, we excised the amygdala, hippocampus and medial prefrontal cortex, corticolimbic brain regions involved in the stress response, to measure endocannabinoid levels. When AEA levels were altered in response to restraint and swim stress, they were reduced, whereas exposure to foot shock stress led to an increase in the amygdala. 2-AG levels, when they were altered by stress exposure were only increased, specifically in males in the amygdala following swim stress, and in the hippocampus and medial prefrontal cortex overall following foot shock stress. This increase in 2-AG levels following stress only in males was the only sex difference found in stress-induced changes in endocannabinoid levels. There were no consistent sex differences observed. Collectively, these data contribute to our further understanding of the interactions between stress and endocannabinoid function.

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Stressor modality influences acute stress-induced changes in endocannabinoid levels in corticolimbic brain regions.

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There are minimal sex differences with regards to basal levels or stress-induced changes in endocannabinoid levels.

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AEA decreased from acute restraint and swim stresses but increased from acute foot shock stress.

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2-AG levels only showed increases when they were impacted by the different stress modalities.

Serotonin 2A receptors and cannabinoids

Accumulating evidence has proven that both exogenous cannabinoids as well as imbalances in the endocannabinoid system are involved in the onset and development of mental disorders such as anxiety, depression, or schizophrenia. Extensive recent research in this topic has mainly focused on the molecular mechanisms by which cannabinoid agonists may contribute to the pathophysiology of these disorders. Initially, serotonin neurotransmitter garnered most attention due to its relationship to mood disorders and mental diseases, with little attention to specific receptors. To date, the focus has redirected toward the understanding of different serotonin receptors, through a demonstration of its versatile pharmacology and synergy with different modulators. Serotonin 2A receptors are a good example of this phenomenon, and the complex signaling that they trigger appears of high relevance in the context of mental disorders, especially in schizophrenia. This chapter will analyze most relevant attributes of serotonin 2A receptors and the endocannabinoid system, and will highlight the evidence toward the functional bidirectional interaction between these elements in the brain as well as the impact of the endocannabinoid system dysregulation on serotonin 2A receptors functionality.

The Complex Interplay between Endocannabinoid System and the Estrogen System in Central Nervous System and Periphery

The endocannabinoid system (ECS) is a lipid cell signaling system involved in the physiology and homeostasis of the brain and peripheral tissues. Synaptic plasticity, neuroendocrine functions, reproduction, and immune response among others all require the activity of functional ECS, with the onset of disease in case of ECS impairment. Estrogens, classically considered as female steroid hormones, regulate growth, differentiation, and many other functions in a broad range of target tissues and both sexes through the activation of nuclear and membrane estrogen receptors (ERs), which leads to genomic and non-genomic cell responses. Since ECS function overlaps or integrates with many other cell signaling systems, this review aims at updating the knowledge about the possible crosstalk between ECS and estrogen system (ES) at both central and peripheral level, with focuses on the central nervous system, reproduction, and cancer.

Cannabinoids as therapeutics for PTSD

Post-traumatic stress disorder (PTSD) is a complex disorder that involves dysregulation of multiple neurobiological systems. The traumatic stressor plays a causal role in producing psychological dysfunction and the pattern of findings suggests that the hypothalamic-pituitary-adrenal (HPA) axis, which is instrumental for stress adaptation, is critically dysfunctional in PTSD. Given the lack of understanding of the basic mechanisms and underlying pathways that cause the disorder and its heterogeneity, PTSD poses challenges for treatment. Targeting the endocannabinoid (ECB) system to treat mental disorders, and PTSD in particular, has been the focus of research and interest in recent years. The ECB system modulates multiple functions, and drugs enhancing ECB signaling have shown promise as potential therapeutic agents in stress effects and other psychiatric and medical conditions. In this review, we focus on the interaction between the ECB-HPA systems in animal models for PTSD and in patients with PTSD. We summarize evidence supporting the use of cannabinoids in preventing and treating PTSD in preclinical and clinical studies. As the HPA system plays a key role in the mediation of the stress response and the pathophysiology of PTSD, we describe preclinical studies suggesting that enhancing ECB signaling is consistent with decreasing PTSD symptoms and dysfunction of the HPA axis. Overall, we suggest that a pharmacological treatment targeted at one system (e.g., HPA) may not be very effective because of the heterogeneity of the disorder. There are abnormalities across different neurotransmitter systems in the pathophysiology of PTSD and none of these systems function uniformly among all patients with PTSD. Hence, conceptually, enhancing ECB signaling may be a more effective avenue for pharmacological treatment.

Inhibition of fatty acid amide hydrolase by chlorpyrifos in juvenile rats results in altered exploratory and social behavior as adolescents

The organophosphorus insecticide chlorpyrifos (CPF) is suspected to cause developmental neurotoxicity in children leading to long term effects. Developmental exposure of rat pups to CPF at low levels disrupts degradation of the brain endocannabinoids through the inhibition of fatty acid amide hydrolase (FAAH) and decreases the reactivity of juvenile rats in an emergence test. In this study, we further investigated the effects of developmental CPF exposure on behavior but also included exposure to PF-04457845, a specific inhibitor of FAAH, for comparison of behavior altered by FAAH inhibition with behavior altered by CPF. Ten day old rat pups were exposed orally either to 0.5, 0.75, or 1.0 mg/kg CPF or 0.02 mg/kg PF-04457845 daily for 7 days. In an open field (day 23), the high CPF and PF-04457845 groups exhibited increased motor activity but no differences in the time spent in the field's center. In an elevated plus maze (day 29), all treatment groups had increased open arm activity but ethological behaviors associated with anxiety were not altered. Behaviors in the maze associated with increased general activity and exploratory drive were increased. Social interactions (day 36) were measured and all treatment groups exhibited increased levels of play behavior. The similarities in behavior between PF-04457845 and CPF suggest that enhanced endocannabinoid signaling during the exposure period plays a role in the persistent alteration of behavior observed following developmental CPF exposure.

Dual pharmacological inhibitor of endocannabinoid degrading enzymes reduces depressive-like behavior in female rats

Major depressive disorder (MDD) is common, often under-treated and a leading cause of disability and mortality worldwide. The causes of MDD remain unclear, including the role of the endocannabinoid system. Intriguingly, the prevalence of depression is significantly greater in women than men. In this study we examined the role of endocannabinoids in depressive behavior. The levels of endocannabinoids, N-arachidonoyl ethanolamide (AEA) and 2-arachidonoyl glycerol (2-AG) were measured along with brain derived neurotrophic factor (BDNF) in postmortem ventral striata of female patients with MDD and non-psychiatric controls, and in Wistar Kyoto (WKY) rat, a selectively inbred strain of rat widely used for testing the depressive behavior. The effect of pharmacological elevation of endocannabinoids through inhibition of their catabolizing enzymes (fatty acid amide hydrolase [FAAH] and monoacyl glycerol lipase [MAGL]) on depressive-like phenotype was also assessed in WKY rat. The findings showed lower levels of endocannabinoids and BDNF in the ventral striata of MDD patients and WKY rats. A dual inhibitor of FAAH and MAGL, JZL195, elevated the endocannabinoids and BDNF levels in ventral striatum, and reduced the depressive-like phenotype in female WKY rats. Collectively, our study suggests a blunted ventral striatal endocannabinoid and BDNF signaling in depressive behavior and concludes that endocannabinoid enhancing agents may have an antidepressant effect.

The Role of Endocannabinoid System Based on mRNA Expression During the Late Luteal Phase and Estrus in the Bovine Endometrium

There are several findings indicating that the endocannabinoid system (ECS) is an important factor, acting in multiple ways in regulating reproductive function but changes of this system in the bovine endometrium have rarely been investigated; therefore, this study was designed to consider an association between endometrial ECS expression and different stages of the estrous cycles. MRNA expressions of the ECS were investigated during the late luteal phase and estrus using real-time PCR. Following estrous synchronization of sixteen Holstein dairy cows (34±1.3 kg/day of milk production), using two PGF2α injections given 14 days apart, at 30 and 44 days in milk (DIM), blood samples and ultrasonography (US) were performed every other day from the day of second PGF2α injection (44 DIM) until the start of the next estrous cycle (67±2 DIM) to verify CL development and ovulation. Based on blood and US results endometrial tissue was collected on days 16 (late luteal phase) and 21 (estrus) of the synchronized estrous cycle (ovulation = d 0). Real-time PCR analysis of ECS mRNA expression revealed endocannabinoid receptor (CNR2), diacylglycerol lipase (DAGL), cyclooxygenase-2 (COX-2), fatty acid amide hydrolase (FAAH) and monoglyceride lipase (MGLL) had significant fold differences when comparing two different stages of the estrous cycle (late luteal phase vs. estrus). CNR2 and DAGL showed 2.01 and 2.57 fold increase, respectively (P=0.04 and P=0.02), in estrous cows. Among the analyzed genes FAAH (P=0.01) and MGLL (P=0.02) were significantly down-regulated in estrous cows, with a 5.01- and 2.44-fold difference in mRNA expression, respectively. Overall, this study highlights an association between the expression of the ECS in the bovine endometrium and stage of the estrous cycle.

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.

Sex difference in brain CB1 receptor availability in man

The endocannabinoid system (ECS) has a widespread neuromodulatory function in the central nervous system and is involved in important aspects of brain function including brain development, cortical rhythms, plasticity, reward, and stress sensitivity. Many of these effects are mediated via the cannabinoid CB1 receptor (CB1R) subtype. Animal studies convincingly show an interaction between the ECS and sex hormones, as well as a sex difference of higher brain CB1R in males. Human in vivo studies of sex difference have yielded discrepant findings. Gender differences in CB1R availability were investigated in vivo in 11 male and 11 female healthy volunteers using a specific CB1R tracer [¹⁸F]FMPEP-d2 and positron emission tomography (PET). Regional [¹⁸F]FMPEP-d2 distribution volume was used as a proxy for CB1R availability. In addition, we explored whether CB1R availability is linked to neuropsychological functioning. Relative to females, CB1R availability was on average 41% higher in males (p = 0.002) with a regionally specific effect larger in the posterior cingulate and retrosplenial cortices (p = 0.001). Inter-subject variability in CB1R availability was similar in both groups. Voxel-based analyses revealed an inverse association between CB1R availability and visuospatial working memory task performance in both groups (p < 0.001). A CB1R sex difference with a large effect size was observed and should be considered in the design of CB1R-related studies on neuropsychiatric disorders. The behavioural correlates and clinical significance of this difference remain to be further elucidated, but our studies suggest an association between CB1R availability and working memory.

FAAH inhibition attenuates TLR3-mediated hyperthermia, nociceptive- and anxiety-like behaviour in female rats

Aberrant activation of toll-like receptor (TLR)s results in persistent and prolonged neuroinflammation and has been implicated in the pathogenesis and exacerbation of psychiatric and neurodegenerative disorders. TLR3 coordinates the innate immune response to viral infection and recent data have demonstrated that inhibiting fatty acid amide hydrolase (FAAH), the enzyme that primarily metabolizes anandamide, modulates TLR3-mediated neuroinflammation. However, the physiological and behavioural consequences of such modulation are unknown. The present study examined the effect of URB597, a selective FAAH inhibitor, on neuroinflammation, physiological and behavioural alterations following administration of the TLR3 agonist and viral mimetic poly I:C to female rats. URB597 attenuated TLR3-mediated fever, mechanical and cold allodynia, and anxiety-like behaviour in the elevated plus maze and open field arena. There was no effect of URB597 on TLR3-mediated decreases in body weight and no effect in the sucrose preference or forced swim tests. URB597 attenuated the TLR3-mediated increase in the expression of CD11b and CD68, markers of microglia/macrophage activation. In summary, these data demonstrate that enhancing FAAH substrate levels suppresses TLR3-mediated microglia/macrophage activation and associated changes in fever, nociceptive responding and anxiety-related behaviour. These data provide further support for FAAH as a novel therapeutic target for neuroinflammatory disorders.

Integrating Endocannabinoid Signaling and Cannabinoids into the Biology and Treatment of Posttraumatic Stress Disorder

Exposure to stress is an undeniable, but in most cases surmountable, part of life. However, in certain individuals, exposure to severe or cumulative stressors can lead to an array of pathological conditions including posttraumatic stress disorder (PTSD), characterized by debilitating trauma-related intrusive thoughts, avoidance behaviors, hyperarousal, as well as depressed mood and anxiety. In the context of the rapidly changing political and legal landscape surrounding use of cannabis products in the USA, there has been a surge of public and research interest in the role of cannabinoids in the regulation of stress-related biological processes and in their potential therapeutic application for stress-related psychopathology. Here we review the current state of knowledge regarding the effects of cannabis and cannabinoids in PTSD and the preclinical and clinical literature on the effects of cannabinoids and endogenous cannabinoid signaling systems in the regulation of biological processes related to the pathogenesis of PTSD. Potential therapeutic implications of the reviewed literature are also discussed. Finally, we propose that a state of endocannabinoid deficiency could represent a stress susceptibility endophenotype predisposing to the development of trauma-related psychopathology and provide biologically plausible support for the self-medication hypotheses used to explain high rates of cannabis use in patients with trauma-related disorders.

Effects of CB1 receptor antagonism and stress exposures in adolescence on socioemotional behaviours, neuroendocrine stress responses, and expression of relevant proteins in the hippocampus and prefrontal cortex in rats

Little is known about the consequences of altered endocannabinoid signalling in adolescence. We hypothesized that CB1 receptor antagonism (AM251, 1 mg/kg) and stress exposures (1 h confinement stress) in adolescence (daily, postnatal days 30-44) would interact to increase neuroendocrine stress responses and anxiety when investigated a minimum of 24 h after drug and stress treatments; these treatment effects were independent of each other. Changes in homecage behaviour and in weight gain confirmed that both males and females were sensitive to the treatments. Nevertheless, in males, repeated AM251 administration was without effect on any of the measures investigated in days post-treatment. Males had reduced corticosterone release to the repeated stress and had increased GAD67 expression in the ventral hippocampus under baseline conditions. In females, AM251 also reduced weight gain and increased stereotypic behaviours in the homecage; these same females showed increased sociality, reduced CB1 receptor expression in the dorsal hippocampus, and increased GAD67 expression in the prefrontal cortex. Further, females exposed to repeated stress had enhanced recovery to baseline corticosterone concentrations after stress. The inclusion of a non-injected comparison group also revealed stress of injection effects in both sexes that otherwise would have been masked. Together, the findings demonstrate effects of CB1 receptor antagonism and stress that were more evident in females than males, suggesting that females may be more vulnerable to the consequences of disrupted endocannabinoid signalling during adolescence.

Sex- and hormone-dependent alterations in alcohol withdrawal-induced anxiety and corticolimbic endocannabinoid signaling

Alcohol dependence is associated with anxiety during withdrawal. The endocannabinoid (ECB) system participates in the neuroendocrine and behavioral response to stress and changes in corticolimbic ECB signaling may contribute to alcohol withdrawal-induced anxiety. Moreover, symptoms of alcohol withdrawal differ between sexes and sexual dimorphism in withdrawal-induced ECB recruitment may be a contributing factor. Herein, we exposed intact male and female rats and ovariectomized (OVX) female rats with or without estradiol (E₂) replacement to 6 weeks of chronic intermittent alcohol vapor and measured anxiety-like behavior, ECB content, and ECB-related mRNA in the basolateral amygdala (BLA) and ventromedial prefrontal cortex (vmPFC). Acute alcohol withdrawal increased anxiety-like behavior, produced widespread disturbances in ECB-related mRNA, and reduced anandamide (AEA) content in the BLA and 2-arachidonoylglycerol (2-AG) content in the vmPFC of male, but not female rats. Similar to males, alcohol-exposed OVX females showed reductions in Napepld mRNA in the BLA, decreased AEA content in the BLA and vmPFC, and reductions in all ECB-related genes measured in the vmPFC. Importantly, E₂ replacement prevented withdrawal-induced alterations in ECB content (but not mRNA) in OVX females, and although alcohol-exposed OVX females failed to exhibit more anxiety compared to their respective control, chronic alcohol exposure abolished the anxiolytic properties of E₂ in OVX rats. These data indicate that ovarian sex hormones (but not E₂ alone) protect against withdrawal-induced alterations in corticolimbic ECB signaling but do not impart resilience to withdrawal-induced anxiety. Thus, the mechanisms implicated in the manifestation of alcohol withdrawal-induced anxiety are most likely sex-specific. This article is part of the Special Issue entitled "A New Dawn in Cannabinoid Neurobiology".

Seeing through the smoke: Human and animal studies of cannabis use and endocannabinoid signalling in corticolimbic networks

Public opinion surrounding the recreational use and therapeutic potential of cannabis is shifting. This review describes new work examining the behavioural and neural effects of cannabis and the endocannabinoid system, highlighting key regions within corticolimbic brain circuits. First, we consider the role of human genetic factors and cannabis strain chemotypic differences in contributing to interindividual variation in the response to cannabinoids, such as THC, and review studies demonstrating that THC-induced impairments in decision-making processes are mediated by actions at prefrontal CB1 receptors. We further describe evidence that signalling through prefrontal or ventral hippocampal CB1 receptors modulates mesolimbic dopamine activity, aberrations of which may contribute to emotional processing deficits in schizophrenia. Lastly, we review studies suggesting that endocannabinoid tone in the amygdala is a critical regulator of anxiety, and report new data showing that FAAH activity is integral to this response. Together, these findings underscore the importance of cannabinoid signalling in the regulation of cognitive and affective behaviours, and encourage further research given their social, political, and therapeutic implications.

The anxiolytic effect of essential oil of Cananga odorata exposure on mice and determination of its major active constituents

BACKGROUND

Essential oil from Cananga odorata (ylang-ylang essential oil, YYO) is usually used in reducing blood pressure, improving cognitive functioning in aromatherapy in human. Few reports showed its effect on anxiety behaviors.

HYPOTHESIS/PURPOSE

To investigate the anxiolytic effects of YYO exposure on anxiety animal models, determine the major active constituents and investigate the change of neurotransmitters after odor exposure.

STUDY DESIGN AND METHODS

ICR mice were subjected to three anxiety models including open field, elevated plus maze and light-dark box tests after acute and chronic YYO exposure. Main constituents of YYO were defined using GC/MS. These compounds were then tested on the male mice separately on three anxiety models. The monoamines neurotransmitters and their metabolites were analyzed after acute odor exposure and elevated plus maze test.

RESULTS

YYO exposure only showed significant anxiolytic effect on the male mice. It increased the time that mice visited open arms and light box area in elevated plus maze and light-dark box tests after acute and chronic YYO exposures. Three main constituents of YYO, benzyl benzoate, linalool and benzyl alcohol showed anxiolytic effect on the male mice individually. YYO exposure brought changes of neurotransmitters on the male mice more significantly than the female mice. It decreased the dopamine (DA) concentration in the striatum and increased the 5-hydroxytryptamine (5-HT) concentration in the hippocampus of the male mice. The major constituent benzyl benzoate changed neurotransmitters concentration in accordance with the YYO. Moreover, it decreased the ratio of 5-HIAA/5-HT in the hippocampus.

CONCLUSION

Both acute and chronic YYO exposure showed anxiolytic effect on the male mice. YYO and its major constituent benzyl benzoate might act on the 5-HTnergic and DAnergic pathways.

Estradiol impacts the endocannabinoid system in female rats to influence behavioral and structural responses to cocaine

Compared with men, women show enhanced responses to drugs of abuse, and consequently are thought to be more vulnerable to addiction. The ovarian hormone estradiol has emerged as a key facilitator in the heightened development of addiction in females. These actions of estradiol appear mediated by estrogen receptor (ER) activation of metabotropic glutamate receptor type 5 (mGluR5). However, the downstream effectors of this ER/mGluR5 signaling pathway are unknown. Here we investigate whether cannabinoid 1 receptor (CB1R) activation is a part of the mechanism whereby estradiol influences behavioral and synaptic correlates of addiction. Following repeated cocaine administration, estradiol-treated ovariectomized rats exhibited both sensitized locomotor responses and decreases in the dendritic spine density of nucleus accumbens core medium-spiny neurons in comparison to oil-treated controls. Both effects of estradiol were blocked by AM251, a CB1R inverse agonist. These results indicate that part of the signaling mechanism through which estradiol impacts behavioral and synaptic correlates of addiction in female rats requires activation of CB1Rs.

Genetic variants associated with physical and mental characteristics of the elite athletes in the Polish population

The aim of the study was to assess whether selected genetic variants are associated with elite athlete performance in a group of 413 elite athletes and 451 sedentary controls. Polymorphisms in ACE, ACTN3, AGT, NRF-2, PGC1A, PPARG, and TFAM implicated in physical performance traits were analyzed. Additionally, polymorphisms in CHRNB3 and FAAH coding for proteins modulating activity of brain's emotion centers were included. The results of univariate analyses indicated that the elite athletic performance is associated with four polymorphisms: ACE (rs4341, P = 0.0095), NRF-2 (rs12594956, P = 0.011), TFAM (rs2306604, P = 0.049), and FAAH (rs324420, P = 0.0041). The multivariate analysis adjusted for age and gender confirmed this association. The higher number of ACE D alleles (P = 0.0021) and the presence of NRF-2 rs12594956 A allele (P = 0.0067) are positive predictors, whereas TFAM rs2306604 GG genotype (P = 0.031) and FAAH rs324420 AA genotype (P = 0.0084) negatively affect the elite athletic performance. The CHRNB3 variant (rs4950, G allele) is significantly more frequent in the endurance athletes compared with the power ones (P = 0.025). Multivariate analysis demonstrated that the presence of rs4950 G allele contributes to endurance performance (P = 0.0047). Our results suggest that genetic inheritance of psychological traits should be taken into consideration while trying to decipher a genetic profile of top athletic performance.

Developmental regulation of fear learning and anxiety behavior by endocannabinoids

The developing brain undergoes substantial maturation into adulthood and the development of specific neural structures occurs on differing timelines. Transient imbalances between developmental trajectories of corticolimbic structures, which are known to contribute to regulation over fear learning and anxiety, can leave an individual susceptible to mental illness, particularly anxiety disorders. There is a substantial body of literature indicating that the endocannabinoid (eCB) system critically regulates stress responsivity and emotional behavior throughout the life span, making this system a novel therapeutic target for stress- and anxiety-related disorders. During early life and adolescence, corticolimbic eCB signaling changes dynamically and coincides with different sensitive periods of fear learning, suggesting that eCB signaling underlies age-specific fear learning responses. Moreover, perturbations to these normative fluctuations in corticolimbic eCB signaling, such as stress or cannabinoid exposure, could serve as a neural substrate contributing to alterations to the normative developmental trajectory of neural structures governing emotional behavior and fear learning. In this review, we first introduce the components of the eCB system and discuss clinical and rodent models showing eCB regulation of fear learning and anxiety in adulthood. Next, we highlight distinct fear learning and regulation profiles throughout development and discuss the ontogeny of the eCB system in the central nervous system, and models of pharmacological augmentation of eCB signaling during development in the context of fear learning and anxiety.

Sex-dependence of anxiety-like behavior in cannabinoid receptor 1 (Cnr1) knockout mice

Epidemiological data suggest women are at increased risk for developing anxiety and depression, although the mechanisms for this sex/gender difference remain incompletely understood. Pre-clinical studies have begun to investigate sex-dependent emotional learning and behavior in rodents, particularly as it relates to psychopathology; however, information about how gonadal hormones interact with the central nervous system is limited. We observe greater anxiety-like behavior in male mice with global knockout of the cannabinoid 1 receptor (Cnr1) compared to male, wild-type controls as measured by percent open arm entries on an elevated plus maze test. A similar increase in anxiety-like behavior, however, is not observed when comparing female Cnr1 knockouts to female wild-type subjects. Although, ovariectomy in female mice did not reverse this effect, both male and female adult mice with normative development were sensitive to Cnr1 antagonist-mediated increases in anxiety-like behavior. Together, these data support an interaction between sex, potentially mediated by gonadal hormones, and the endocannabinoid system at an early stage of development that is critical for establishing adult anxiety-like behavior.

Effects of CB1 receptor agonism and antagonism on behavioral fear and physiological stress responses in adult intact, ovariectomized, and estradiol-replaced female rats

There is growing interest in the development of cannabis-based therapies for the treatment of fear and anxiety disorders. There are a few studies, but none in females, of the effects of the highly selective cannabinoid receptor type 1 (CB1) agonist, arachidonyl 2'-chlorethylamide (ACEA), on behavioral fear. In experiment 1 involving gonadally-intact females, ACEA (either 0.1 or 0.01 mg/kg) was without effect in the elevated plus maze (EPM), and the lower dose decreased anxiety in the open field test (OFT). AM251 increased anxiety in the EPM and decreased locomotor activity in the OFT. Twenty-four hours after fear conditioning, neither ACEA nor AM251 affected generalized fear or conditioned fear recall. AM251 and 0.1 mg/kg ACEA impaired, and 0.01 mg/kg ACEA enhanced, within-session fear extinction. AM251 increased plasma corticosterone concentrations after the fear extinction session, whereas ACEA was without effect. Based on evidence that estradiol may moderate the effects of CB1 receptor signaling in females, experiment 2 involved ovariectomized (OVX) rats provided with 10-μg 17β-Estradiol and compared with OVX rats without hormone replacement (oil vehicle). Irrespective of hormone treatment, AM251 increased anxiety in the EPM, whereas ACEA (0.01 mg/kg) was without effect. Neither hormone nor drug altered anxiety in the OFT, but estradiol increased and AM251 decreased distance traveled. After fear conditioning, AM251 decreased generalized fear. Neither hormone nor drug had any effect on recall or extinction of conditioned fear, however, ACEA and AM251 increased fear-induced plasma corticosterone concentrations. Further, when results with intact rats were compared with those from OVX rats, gonadal status did not moderate the effects of either AM251 or ACEA, although OVX displayed greater anxiety and fear than did intact rats. Thus, the effects of CB1 receptor antagonism and agonism in adult female rats do not depend on ovarian estradiol.

Distinct roles of the endocannabinoids anandamide and 2-arachidonoylglycerol in social behavior and emotionality at different developmental ages in rats

To date, our understanding of the relative contribution and potential overlapping roles of the endocannabinoids anandamide (AEA) and 2-arachidonoylglycerol (2-AG) in the regulation of brain function and behavior is still limited. To address this issue, we investigated the effects of systemic administration of JZL195, that simultaneously increases AEA and 2-AG signaling by inhibiting their hydrolysis, in the regulation of socio-emotional behavior in adolescent and adult rats. JZL195, administered at the dose of 0.01mg/kg, increased social play behavior, that is the most characteristic social activity displayed by adolescent rats, and increased social interaction in adult animals. At both ages, these behavioral effects were antagonized by the CB1 cannabinoid receptor antagonist SR141716A and were associated with increased brain levels of 2-AG, but not AEA. Conversely, at the dose of 1mg/kg, JZL195 decreased general social exploration in adolescent rats without affecting social play behavior, and induced anxiogenic-like effects in the elevated plus-maze test both in adolescent and adult animals. These effects, mediated by activation of CB1 cannabinoid receptors, were paralleled by simultaneous increase in AEA and 2-AG levels in adolescent rats, and by an increase of only 2-AG levels in adult animals. These findings provide the first evidence for a role of 2-AG in social behavior, highlight the different contributions of AEA and 2-AG in the modulation of emotionality at different developmental ages and suggest that pharmacological inhibition of AEA and 2-AG hydrolysis is a useful approach to investigate the role of these endocannabinoids in neurobehavioral processes.

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.

Translational evidence for a role of endocannabinoids in the etiology and treatment of posttraumatic stress disorder

INTRODUCTION

Posttraumatic stress disorder (PTSD) is a prevalent, chronic, and disabling anxiety disorder that may develop following exposure to a traumatic event. Despite the public health significance of PTSD, relatively little is known about the etiology or pathophysiology of this disorder, and pharmacotherapy development to date has been largely opportunistic instead of mechanism-based. Recently, an accumulating body of evidence has implicated the endocannabinoid system in the etiology of PTSD, and targets within this system are believed to be suitable for treatment development.

METHODS

Herein, we describe evidence from translational studies arguing for the relevance of the endocannabinoid system in the etiology of PTSD. We also show mechanisms relevant for treatment development.

RESULTS

There is convincing evidence from multiple studies for reduced endocannabinoid availability in PTSD. Brain imaging studies show molecular adaptations with elevated cannabinoid type 1 (CB1) receptor availability in PTSD which is linked to abnormal threat processing and anxious arousal symptoms.

CONCLUSION

Of particular relevance is evidence showing reduced levels of the endocannabinoid anandamide and compensatory increase of CB1 receptor availability in PTSD, and an association between increased CB1 receptor availability in the amygdala and abnormal threat processing, as well as increased severity of hyperarousal, but not dysphoric symptomatology, in trauma survivors. Given that hyperarousal symptoms are the key drivers of more disabling aspects of PTSD such as emotional numbing or suicidality, novel, mechanism-based pharmacotherapies that target this particular symptom cluster in patients with PTSD may have utility in mitigating the chronicity and morbidity of the disorder.

Strain- and context-dependent effects of the anandamide hydrolysis inhibitor URB597 on social behavior in rats

Genetic and environmental factors play an important role in the cannabinoid modulation of motivation and emotion. Therefore, the aim of the present study was to test whether anandamide modulation of social behavior is strain- and context-dependent. We tested the effects of the anandamide hydrolysis inhibitor URB597 on social behavior and 50-kHz ultrasonic vocalizations (USVs) in adolescent and adult Wistar and Sprague-Dawley rats tested in different emotionally arousing conditions (familiarity/unfamiliarity to the test cage, low/high light). Under all experimental conditions, adolescent and adult Sprague-Dawley rats displayed higher levels of social behavior and emitted more 50-kHz USVs than Wistar rats. URB597 enhanced social play behavior in adolescent Wistar rats under all experimental conditions. However, URB597 only increased social interaction in adult Wistar rats under unfamiliar/high light conditions. URB597 did not affect adolescent social play behavior and adult social interaction in Sprague-Dawley rats under any experimental condition. Moreover, URB597 increased the USVs emitted during social interaction by adolescent Wistar and adult Sprague-Dawley rats tested under familiar/high light and unfamiliar/high light, respectively. These results show that anandamide has distinct roles in adolescent and adult social behaviors. Anandamide modulation of adolescent social play behavior is strain- but not context-dependent. Conversely, anandamide modulation of adult social behavior and USV emission depends upon both strain and experimental context. Furthermore, these results confirm that profound behavioral differences exist between Wistar and Sprague-Dawley rats, which may explain the sometimes contradictory effects of cannabinoid drugs on emotionality in different strains of rodents.

Updates in reproduction coming from the endocannabinoid system

The endocannabinoid system (ECS) is an evolutionarily conserved master system deeply involved in the central and local control of reproductive functions in both sexes. The tone of these lipid mediators-deeply modulated by the activity of biosynthetic and hydrolyzing machineries-regulates reproductive functions from gonadotropin discharge and steroid biosynthesis to the formation of high quality gametes and successful pregnancy. This review provides an overview on ECS and reproduction and focuses on the insights in the regulation of endocannabinoid production by steroids, in the regulation of male reproductive activity, and in placentation and parturition. Taken all together, evidences emerge that the activity of the ECS is crucial for procreation and may represent a target for the therapeutic exploitation of infertility.

Amygdala FAAH and anandamide: mediating protection and recovery from stress

A long-standing literature linking endocannabinoids (ECBs) to stress, fear, and anxiety has led to growing interest in developing novel anxiolytics targeting the ECB system. Following rapid on-demand biosynthesis and degradation upon neuronal activation, the ECB N-arachidonoylethanolamide (anandamide, AEA) is actively degraded by the serine hydrolase enzyme, fatty acid amide hydrolase (FAAH). Exposure to stress rapidly mobilizes FAAH to deplete the signaling pool of AEA and increase neuronal excitability in a key anxiety-mediating region--the basolateral amygdala (BLA). Gene deletion or pharmacological inhibition of FAAH prevents stress-induced reductions in AEA and associated increases in BLA dendritic hypertrophy and anxiety-like behavior. Additionally, inhibition of FAAH facilitates long-term fear extinction and rescues deficient fear extinction in rodent models by enhancing AEA-CB1 (cannabinoid type 1) receptor signaling and synaptic plasticity in the BLA. These preclinical findings propose restoring deficient BLA AEA levels by pharmacologically inhibiting FAAH as a mechanism to therapeutically mitigate the effects of traumatic stress.

Translational evidence for the involvement of the endocannabinoid system in stress-related psychiatric illnesses

Accumulating evidence over the past decade has highlighted an important role of the endocannabinoid (eCB) system in the regulation of stress and emotional behavior across divergent species, from rodents to humans. The general findings from this work indicate that the eCB system plays an important role in gating and buffering the stress response, dampening anxiety and regulating mood. Work in rodents has allowed researchers to determine the neural mechanisms mediating this relationship while work in human populations has demonstrated the possible importance of this system in stress-related psychiatric diseases, such as post-traumatic stress disorder, generalized anxiety and major depression. These stress-protective effects of eCB signaling appear to be primarily mediated by their actions within corticolimbic structures, particularly the amygdala and the prefrontal cortex. The aim of this review is to provide an up-to-date discussion of the current level of knowledge in this field, as well as address the current gaps in knowledge and specific areas of research that require attention.

Disruption of fatty acid amide hydrolase activity prevents the effects of chronic stress on anxiety and amygdalar microstructure

Hyperactivation of the amygdala following chronic stress is believed to be one of the primary mechanisms underlying the increased propensity for anxiety-like behaviors and pathological states; however, the mechanisms by which chronic stress modulates amygdalar function are not well characterized. The aim of the current study was to determine the extent to which the endocannabinoid (eCB) system, which is known to regulate emotional behavior and neuroplasticity, contributes to changes in amygdalar structure and function following chronic stress. To examine the hypothesis, we have exposed C57/Bl6 mice to chronic restraint stress, which results in an increase in fatty acid amide hydrolase (FAAH) activity and a reduction in the concentration of the eCB N-arachidonylethanolamine (AEA) within the amygdala. Chronic restraint stress also increased dendritic arborization, complexity and spine density of pyramidal neurons in the basolateral nucleus of the amygdala (BLA) and increased anxiety-like behavior in wild-type mice. All of the stress-induced changes in amygdalar structure and function were absent in mice deficient in FAAH. Further, the anti-anxiety effect of FAAH deletion was recapitulated in rats treated orally with a novel pharmacological inhibitor of FAAH, JNJ5003 (50 mg per kg per day), during exposure to chronic stress. These studies suggest that FAAH is required for chronic stress to induce hyperactivity and structural remodeling of the amygdala. Collectively, these studies indicate that FAAH-mediated decreases in AEA occur following chronic stress and that this loss of AEA signaling is functionally relevant to the effects of chronic stress. These data support the hypothesis that inhibition of FAAH has therapeutic potential in the treatment of anxiety disorders, possibly by maintaining normal amygdalar function in the face of chronic stress.

Screening genetic variability at the CNR1 gene in both major depression etiology and clinical response to citalopram treatment

RATIONALE

The endocannabinoid system has been implicated in the pathogenesis of major depression (MD) as well as in the mediation of antidepressant drug effects.

OBJECTIVES

To analyze CNR1 gene variants in MD and clinical response to citalopram (selective serotonin re-uptake inhibitors [SSRI]).

METHODS

The role of CNR1 gene (rs806368, rs1049353, rs806371, rs806377 and rs1535255) was investigated in 319 outpatients with MD and 150 healthy individuals. A subsample of 155 depressive patients were treated with citalopram and evaluated for response (fourth week) and remission (12th week) by the 21-item Hamilton Depression Rating Scale (HDRS).

RESULTS

We observed a higher frequency of rs806371 G carriers in MD patients with both presence of melancholia (p = 0.018) and psychotic symptoms (p = 0.007) than in controls. Haplotype frequency distributions between MD sample and controls showed a significant difference for Block 1 (rs806368-rs1049353-rs806371) (p = 0.008). This haplotype finding was consistent when we compared controls with MD subsample stratified by melancholia (p = 0.0009) and psychotic symptoms (p = 0.014). The TT homozygous of the rs806368 and rs806371 presented more risk of no Remission than the C carriers (p = 0.008 and 0.012, respectively). Haplotype frequency distributions according to Remission status showed a significant difference for Block 1 (p = 0.032). Also, we observed significant effect of time-sex-genotype interaction for the rs806368, showing that the C carrier men presented a better response to antidepressant treatment throughout the follow-up than TT homozygous men and women group (p = 0.026).

CONCLUSIONS

These results suggest an effect of CNR1 gene in the etiology of MD and clinical response to citalopram.