Type-1 cannabinoid receptor signaling in neuronal development

Local glycolysis fuels actomyosin contraction during axonal retraction

In response to repulsive cues, axonal growth cones can quickly retract. This requires the prompt activity of contractile actomyosin, which is formed by the non-muscle myosin II (NMII) bound to actin filaments. NMII is a molecular motor that provides the necessary mechanical force at the expense of ATP. Here, we report that this process is energetically coupled to glycolysis and is independent of cellular ATP levels. Induction of axonal retraction requires simultaneous generation of ATP by glycolysis, as shown by chemical inhibition and genetic knock-down of GAPDH. Co-immunoprecipitation and proximal-ligation assay showed that actomyosin associates with ATP-generating glycolytic enzymes and that this association is strongly enhanced during retraction. Using microfluidics, we confirmed that the energetic coupling between glycolysis and actomyosin necessary for axonal retraction is localized to the growth cone and near axonal shaft. These results indicate a tight coupling between on-demand energy production by glycolysis and energy consumption by actomyosin contraction suggesting a function of glycolysis in axonal guidance.

Prenatal cannabinoid exposure: why expecting individuals should take a pregnancy pause from using cannabinoid products

Cannabinoid use in all populations is increasing as legalization across the United States continues. Concerningly, there is a lack of caution provided by medical providers to pregnant individuals as to the impact the use of cannabinoids could have on the developing fetus. Research continues in both the preclinical and clinical areas, and is severely needed, as the potency of delta-9-tetrahydrocannabinol (THC), the primary psychoactive component of cannabis, has increased dramatically since the initial studies were completed. Thus far, clinical studies raise compelling evidence for short term memory deficits, impulse control issues, and attention deficiencies following prenatal cannabinoid exposure (PCE). These changes may be mediated through epigenetic modifications that not only impact the current offspring but could carry forward to future generations. While additional studies are needed, a pregnancy pause from cannabinoid products should be strongly recommended by providers to ensure the optimal health and well-being of our future generations.

The Long-Term Neuroprotective Effect of the Endocannabinoid 2-AG and Modulation of the SGZ's Neurogenic Response after Neonatal Hypoxia-Ischemia

Neonatal hypoxia-ischemia (HI) often causes hypoxic-ischemic encephalopathy (HIE), a neurological condition that can lead to overall disability in newborns. The only treatment available for affected neonates is therapeutic hypothermia; however, cooling is not always effective to prevent the deleterious effects of HI, so compounds such as cannabinoids are currently under research as new therapies. Modulating the endocannabinoid system (ECS) may reduce brain damage and/or stimulate cell proliferation at the neurogenic niches. Further, the long-term effects of cannabinoid treatment are not so clear. Here, we studied the middle- and long-term effects of 2-AG, the most abundant endocannabinoid in the perinatal period after HI in neonatal rats. At middle-term (postnatal day 14), 2-AG reduced brain injury and increased SGZ's cell proliferation and the number of neuroblasts. At post-natal day 90, the treatment with the endocannabinoid showed global and local protection, suggesting long-lasting neuroprotective effects of 2-AG after neonatal HI in rats.

Cell-autonomous and differential endocannabinoid signaling impacts the development of presynaptic retinal ganglion cell axon connectivity in vivo

Cannabis exposure during gestation evokes significant molecular modifications to neurodevelopmental programs leading to neurophysiological and behavioral abnormalities in humans. The main neuronal receptor for Δ⁹-tetrahydrocannabinol (THC) is the type-1 cannabinoid receptor CB₁R, one of the most abundant G-protein-coupled receptors in the nervous system. While THC is the major psychoactive phytocannabinoid, endocannabinoids (eCBs) are the endogenous ligands of CB₁R and are known to act as retrograde messengers to modulate synaptic plasticity at different time scales in the adult brain. Accumulating evidence indicates that eCB signaling through activation of CB₁R plays a central role in neural development. During development, most CB₁R localized to axons of projection neurons, and in mice eCB signaling impacts axon fasciculation. Understanding of eCB-mediated structural plasticity during development, however, requires the identification of the precise spatial and temporal dynamics of CB₁R-mediated modifications at the level of individual neurons in the intact brain. Here, the cell-autonomous role of CB₁R and the effects of CB₁R-mediated eCB signaling were investigated using targeted single-cell knockdown and pharmacologic treatments in Xenopus. We imaged axonal arbors of retinal ganglion cells (RGCs) in real time following downregulation of CB₁R via morpholino (MO) knockdown. We also analyzed RGC axons with altered eCB signaling following treatment with URB597, a selective inhibitor of the enzyme that degrades Anandamide (AEA), or JZL184, an inhibitor of the enzyme that blocks 2-Arachidonoylglycerol (2-AG) hydrolysis, at two distinct stages of retinotectal development. Our results demonstrate that CB₁R knockdown impacts RGC axon branching at their target and that differential 2-AG and AEA-mediated eCB signaling contributes to presynaptic structural connectivity at the time that axons terminate and when retinotectal synaptic connections are made. Altering CB₁R levels through CB₁R MO knockdown similarly impacted dendritic morphology of tectal neurons, thus supporting both pre- and postsynaptic cell-autonomous roles for CB₁R-mediated eCB signaling.

Cannabis in Adolescence: Lasting Cognitive Alterations and Underlying Mechanisms

Cannabis consumption during adolescence is an area of particular concern, owing to changes in the social and political perception of the drug, and presents a scientific, medical, and economic challenge. Major social and economic interests continue to push toward cannabis legalization as well as pharmaceutical development. As a result, shifting perceptions of both legal and illicit cannabis use across the population have changed the collective evaluation of the potential dangers of the product. The wave of cannabis legalization therefore comes with new responsibility to educate the public on potential risks and known dangers associated with both recreational and medical cannabis. Among these is the risk of long-term cognitive and psychological consequences, particularly following early-life initiation of use, compounded by high-potency and/or synthetic cannabis, and heavy/frequent use of the drug. Underlying these cognitive and psychiatric consequences are lasting aberrations in the development of synaptic function, often secondary to epigenetic changes. Additional factors such as genetic risk and environmental influences or nondrug toxic insults during development are also profound contributors to these long-term functional alterations following adolescent cannabis use. Preclinical studies indicate that exposure to cannabinoids during specific windows of vulnerability (e.g., adolescence) impacts neurodevelopmental processes and behavior by durably changing dendritic structure and synaptic functions, including those normally mediated by endogenous cannabinoids and neuronal circuits.

Phytocannabinoids, the Endocannabinoid System and Male Reproduction

The endocannabinoid system (ECS) is comprised of a set of lipid-derived messengers (the endocannabinoids, ECBs), proteins that control their production and degradation, and cell-surface cannabinoid (CB) receptors that transduce their actions. ECB molecules such as 2-arachidonoyl-sn-glycerol (2-AG) and anandamide (arachidonoyl ethanolamide) are produced on demand and deactivated through enzymatic actions tightly regulated both temporally and spatially, serving homeostatic roles in order to respond to various challenges to the body. Key components of the ECS are present in the hypothalamus-pituitary-gonadal (HPG) axis, which plays critical roles in the development and regulation of the reproductive system in both males and females. ECB signaling controls the action at each stage of the HPG axis through CB receptors expressed in the hypothalamus, pituitary, and reproductive organs such as the testis and ovary. It regulates the secretion of hypothalamic gonadotropin-releasing hormone (GnRH), pituitary follicle-stimulating hormone (FSH) and luteinizing hormone (LH), estrogen, testosterone, and affects spermatogenesis in males. Δ⁹-tetrahydrocannabinol (THC) and other phytocannabinoids from Cannabis sativa affect a variety of physiological processes by altering, or under certain conditions hijacking, the ECB system. Therefore, phytocannabinoids, in particular THC, may modify the homeostasis of the HPG axis by altering CB receptor signaling and cause deficits in reproductive function. While the ability of phytocannabinoids, THC and/or cannabidiol (CBD), to reduce pain and inflammation provides promising opportunities for therapeutic intervention for genitourinary and degenerative disorders, important questions remain regarding their unwanted long-term effects. It is nevertheless clear that the therapeutic potential of modulating the ECS calls for further scientific and clinical investigation.

The Endocannabinoid System as a Target for Neuroprotection/Neuroregeneration in Perinatal Hypoxic-Ischemic Brain Injury

The endocannabinoid (EC) system is a complex cell-signaling system that participates in a vast number of biological processes since the prenatal period, including the development of the nervous system, brain plasticity, and circuit repair. This neuromodulatory system is also involved in the response to endogenous and environmental insults, being of special relevance in the prevention and/or treatment of vascular disorders, such as stroke and neuroprotection after neonatal brain injury. Perinatal hypoxia-ischemia leading to neonatal encephalopathy is a devastating condition with no therapeutic approach apart from moderate hypothermia, which is effective only in some cases. This overview, therefore, gives a current description of the main components of the EC system (including cannabinoid receptors, ligands, and related enzymes), to later analyze the EC system as a target for neonatal neuroprotection with a special focus on its neurogenic potential after hypoxic-ischemic brain injury.

Animal evidence considered in determination of cannabis smoke and Δ9 -tetrahydrocannabinol as causing reproductive toxicity (developmental endpoint): Part III. Proposed neurodevelopmental mechanisms of action

This review summarizes the most common potential pathways of neurodevelopmental toxicity due to perinatal exposure to Δ⁹ -tetrahydrocannabinol (Δ⁹ -THC) that lead to behavioral and other adverse outcomes (AOs). This is Part III in a set of reviews highlighting the animal-derived data considered by California's Developmental and Reproductive Toxicant Identification Committee (DARTIC) in 2019. The Hazard Identification Document (HID) provided to the DARTIC included a summary of human, whole animal, and mechanistic data on the neurodevelopmental toxicity of cannabis smoke and Δ⁹ -THC. The literature search for mechanistic data has been updated through 2020. We focus on mechanistic pathways relating to behavioral and other neurodevelopmental outcomes of perinatal exposure to Δ⁹ -THC. The endocannabinoid system (EC system) plays a crucial role in many processes involved in neurodevelopment and exposure to Δ⁹ -THC can alter these processes. Whole animal studies report changes in cognitive ability, behavior, and motor function after prenatal exposure to Δ⁹ -THC. Findings from mechanistic studies add to this evidence and further provide information regarding the pathways leading to these outcomes. Neuromechanistic studies can bridge the gaps between molecular initiating events and apical neurodevelopmental endpoints caused by a chemical. They offer insight into potential alterations in the same pathways by other chemicals that can also result in AOs. Studies of cannabinoid receptor agonist-induced molecular alterations and provide deep biological plausibility at the mechanistic level for the cognitive, behavioral, and motor impairments observed in animal studies after perinatal exposure to Δ⁹ -THC.

Cannabinoid Receptor 1 Is Required for Neurodevelopment of Striosome-Dendron Bouquets

Cannabinoid receptor 1 (CB1R) has strong effects on neurogenesis and axon pathfinding in the prenatal brain. Endocannabinoids that activate CB1R are abundant in the early postnatal brain and in mother's milk, but few studies have investigated their function in newborns. We examined postnatal CB1R expression in the major striatonigral circuit from striosomes of the striatum to the dopamine-containing neurons of the substantia nigra. CB1R enrichment was first detectable between postnatal day (P)5 and P7, and this timing coincided with the formation of "striosome-dendron bouquets," the elaborate anatomic structures by which striosomal neurons control dopaminergic cell activity through inhibitory synapses. In Cnr1^-/- knock-out mice lacking CB1R expression, striosome-dendron bouquets were markedly disorganized by P11 and at adulthood, suggesting a postnatal pathfinding connectivity function for CB1R in connecting striosomal axons and dopaminergic neurons analogous to CB1R's prenatal function in other brain regions. Our finding that CB1R plays a major role in postnatal wiring of the striatonigral dopamine-control system, with lasting consequences at least in mice, points to a crucial need to determine whether lactating mothers' use of CB1R agonists (e.g., in marijuana) or antagonists (e.g., type 2 diabetes therapies) can disrupt brain development in nursing offspring.

Lipid endocannabinoids in energy metabolism, stress and developmental programming

The endocannabinoid system (ECS) regulates brain development and function, energy metabolism and stress in a sex-, age- and tissue-dependent manner. The ECS comprises mainly the bioactive lipid ligands anandamide (AEA) and 2-aracdonoylglycerol (2-AG), cannabinoid receptors 1 and 2 (CB1 and CB2), and several metabolizing enzymes. The endocannabinoid tonus is increased in obesity, stimulating food intake and a preference for fat, reward, and lipid accumulation in peripheral tissues, as well as favoring a positive energy balance. Energy balance and stress responses share adaptive mechanisms regulated by the ECS that seem to underlie the complex relationship between feeding and emotional behavior. The ECS is also a key regulator of development. Environmental insults (diet, toxicants, and stress) in critical periods of developmental plasticity, such as gestation, lactation and adolescence, alter the ECS and may predispose individuals to the development of chronic diseases and behavioral changes in the long term. This review is focused on the ECS and the developmental origins of health and disease (DOHaD).

The Impact of Early Life Exposure to Cannabis: The Role of the Endocannabinoid System

Cannabis use during pregnancy has continued to rise, particularly in developed countries, as a result of the trend towards legalization and lack of consistent, evidence-based knowledge on the matter. While there is conflicting data regarding whether cannabis use during pregnancy leads to adverse outcomes such as stillbirth, preterm birth, low birthweight, or increased admission to neonatal intensive care units, investigations into long-term effects on the offspring’s health are limited. Historically, studies have focused on the neurobehavioral effects of prenatal cannabis exposure on the offspring. The effects of cannabis on other physiological aspects of the developing fetus have received less attention. Importantly, our knowledge about cannabinoid signaling in the placenta is also limited. The endocannabinoid system (ECS) is present at early stages of development and represents a potential target for exogenous cannabinoids in utero. The ECS is expressed in a broad range of tissues and influences a spectrum of cellular functions. The aim of this review is to explore the current evidence surrounding the effects of prenatal exposure to cannabinoids and the role of the ECS in the placenta and the developing fetus.

FMR1 and Autism, an Intriguing Connection Revisited

Autism Spectrum Disorder (ASD) represents a distinct phenotype of behavioral dysfunction that includes deficiencies in communication and stereotypic behaviors. ASD affects about 2% of the US population. It is a highly heritable spectrum of conditions with substantial genetic heterogeneity. To date, mutations in over 100 genes have been reported in association with ASD phenotypes. Fragile X syndrome (FXS) is the most common single-gene disorder associated with ASD. The gene associated with FXS, FMR1 is located on chromosome X. Accordingly, the condition has more severe manifestations in males. FXS results from the loss of function of FMR1 due to the expansion of an unstable CGG repeat located in the 5'' untranslated region of the gene. About 50% of the FXS males and 20% of the FXS females meet the Diagnostic Statistical Manual 5 (DSM-5) criteria for ASD. Among the individuals with ASD, about 3% test positive for FXS. FMRP, the protein product of FMR1, is a major gene regulator in the central nervous system. Multiple pathways regulated by FMRP are found to be dysfunctional in ASD patients who do not have FXS. Thus, FXS presents the opportunity to study cellular phenomena that may have wider applications in the management of ASD and to develop new strategies for ASD therapy.

Neuronal Dystroglycan regulates postnatal development of CCK/cannabinoid receptor-1 interneurons

Background

The development of functional neural circuits requires the precise formation of synaptic connections between diverse neuronal populations. The molecular pathways that allow GABAergic interneuron subtypes in the mammalian brain to initially recognize their postsynaptic partners remain largely unknown. The transmembrane glycoprotein Dystroglycan is localized to inhibitory synapses in pyramidal neurons, where it is required for the proper function of CCK+ interneurons. However, the precise temporal requirement for Dystroglycan during inhibitory synapse development has not been examined.

Methods

In this study, we use NEX^Cre or Camk2a^CreERT2 to conditionally delete Dystroglycan from newly-born or adult pyramidal neurons, respectively. We then analyze forebrain development from postnatal day 3 through adulthood, with a particular focus on CCK+ interneurons.

Results

In the absence of postsynaptic Dystroglycan in developing pyramidal neurons, presynaptic CCK+ interneurons fail to elaborate their axons and largely disappear from the cortex, hippocampus, amygdala, and olfactory bulb during the first two postnatal weeks. Other interneuron subtypes are unaffected, indicating that CCK+ interneurons are unique in their requirement for postsynaptic Dystroglycan. Dystroglycan does not appear to be required in adult pyramidal neurons to maintain CCK+ interneurons. Bax deletion did not rescue CCK+ interneurons in Dystroglycan mutants during development, suggesting that they are not eliminated by canonical apoptosis. Rather, we observed increased innervation of the striatum, suggesting that the few remaining CCK+ interneurons re-directed their axons to neighboring areas where Dystroglycan expression remained intact.

Conclusion

Together these findings show that Dystroglycan functions as part of a synaptic partner recognition complex that is required early for CCK+ interneuron development in the forebrain.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13064-021-00153-1.

Cannabinoid Receptor 1 associates to different molecular complexes during GABAergic neuron maturation

CB₁ cannabinoid receptor is widely expressed in the central nervous system of animals from late prenatal development to adulthood. Appropriate activation and signaling of CB₁ cannabinoid receptors in cortical interneurons are crucial during perinatal/postnatal ages and adolescence, when long-lasting changes in brain activity may elicit subsequent appearance of disorders in the adult brain. Here we used an optimized immunoprecipitation protocol based on specific antibodies followed by shot-gun proteomics to find CB₁ interacting partners in postnatal rat GABAergic cortical neurons in vitro at two different stages of maturation. Besides describing new proteins associated with CB₁ like dihydrolipoyllysine-residue acetyltransferase component of pyruvate dehydrogenase complex (DLAT), fatty acid synthase (FASN), tyrosine 3-monooxygenase/tryptophan 5-monooxygenase activation protein zeta (YWHAZ), voltage-dependent anion channel 1 (VDAC1), myosin phosphatase Rho-interacting protein (MPRIP) or usher syndrome type-1C protein-binding protein 1 (USHBP1), we show that the signaling complex of CB₁ is different between maturational stages. Interestingly, the CB₁ signaling complex is enriched at the more immature stage in mitochondrial associated proteins and metabolic molecular functions, whereas at more mature stage, CB₁ complex is increased in maturation and synaptic-associated proteins. We describe also interacting partners specifically immunoprecipitated with either N-terminal or C-terminal CB₁ directed antibodies. Our results highlight new players that may be affected by altered cannabinoid signaling at this critical window of postnatal cortical development.

Maternal omega-3 intake differentially affects the endocannabinoid system in the progeny`s neocortex and hippocampus: Impact on synaptic markers

Omega-3 (n-3) polyunsaturated fatty acids (PUFA) and the endocannabinoid system (ECS) modulate several functions through neurodevelopment including synaptic plasticity mechanisms. The interplay between n-3PUFA and the ECS during the early stages of development, however, is not fully understood. This study investigated the effects of maternal n-3PUFA supplementation (n-3Sup) or deficiency (n-3Def) on ECS and synaptic markers in postnatal offspring. Female rats were fed with a control, n-3Def, or n-3Sup diet from 15 days before mating and during pregnancy. The cerebral cortex and hippocampus of mothers and postnatal 1-2 days offspring were analyzed. In the mothers, a n-3 deficiency reduced CB1 receptor (CB1R) protein levels in the cortex and increased CB2 receptor (CB2R) in both cortex and hippocampus. In neonates, a maternal n-3 deficiency reduced the hippocampal CB1R amount while it increased CB2R. Additionally, total GFAP isoform expression was increased in both cortex and hippocampus in neonates of the n-3Def group. Otherwise, maternal n-3 supplementation increased the levels of n-3-derived endocannabinoids, DHEA and EPEA, in the cortex and hippocampus and reduced 2-arachidonoyl-glycerol (2-AG) concentrations in the cortex of the offspring. Furthermore, maternal n-3 supplementation also increased PKA phosphorylation in the cortex and ERK phosphorylation in the hippocampus. Synaptophysin immunocontent in both regions was also increased. In vitro assays showed that the increase of synaptophysin in the n-3Sup group was independent of CB1R activation. The findings show that variations in maternal dietary omega-3 PUFA levels may impact differently on the ECS and molecular markers in the cerebral cortex and hippocampus of the progeny.

Cannabinoid Signaling in Auditory Function and Development

Plants of the genus Cannabis have been used by humans for millennia for a variety of purposes. Perhaps most notable is the use of certain Cannabis strains for their psychoactive effects. More recently, several biologically active molecules within the plants of these Cannabis strains, called phytocannabinoids or simply cannabinoids, have been identified. Furthermore, within human cells, endogenous cannabinoids, or endocannabinoids, as well as the receptors and secondary messengers that give rise to their neuromodulatory effects, have also been characterized. This endocannabinoid system (ECS) is composed of two primary ligands-anandamide and 2-arachidonyl glycerol; two primary receptors-cannabinoid receptors 1 and 2; and several enzymes involved in biosynthesis and degradation of endocannabinoid ligands including diacylglycerol lipase (DAGL) and monoacylglycerol lipase (MAGL). Here we briefly summarize cannabinoid signaling and review what has been discerned to date with regard to cannabinoid signaling in the auditory system and its roles in normal physiological function as well as pathological conditions. While much has been uncovered regarding cannabinoid signaling in the central nervous system, less attention has been paid to the auditory system specifically. Still, evidence is emerging to suggest that cannabinoid signaling is critical for the development, maturation, function, and survival of cochlear hair cells (HCs) and spiral ganglion neurons (SGNs). Furthermore, cannabinoid signaling can have profound effects on synaptic connectivity in CNS structures related to auditory processing. While clinical cases demonstrate that endogenous and exogenous cannabinoids impact auditory function, this review highlights several areas, such as SGN development, where more research is warranted.

CB1 antagonism increases excitatory synaptogenesis in a cortical spheroid model of fetal brain development

The endocannabinoid system (ECS) plays a complex role in the development of neural circuitry during fetal brain development. The cannabinoid receptor type 1 (CB1) controls synaptic strength at both excitatory and inhibitory synapses and thus contributes to the balance of excitatory and inhibitory signaling. Imbalances in the ratio of excitatory to inhibitory synapses have been implicated in various neuropsychiatric disorders associated with dysregulated central nervous system development including autism spectrum disorder, epilepsy, and schizophrenia. The role of CB1 in human brain development has been difficult to study but advances in induced pluripotent stem cell technology have allowed us to model the fetal brain environment. Cortical spheroids resemble the cortex of the dorsal telencephalon during mid-fetal gestation and possess functional synapses, spontaneous activity, an astrocyte population, and pseudo-laminar organization. We first characterized the ECS using STORM microscopy and observed synaptic localization of components similar to that which is observed in the fetal brain. Next, using the CB1-selective antagonist SR141716A, we observed an increase in excitatory, and to a lesser extent, inhibitory synaptogenesis as measured by confocal image analysis. Further, CB1 antagonism increased the variability of spontaneous activity within developing neural networks, as measured by microelectrode array. Overall, we have established that cortical spheroids express ECS components and are thus a useful model for exploring endocannabinoid mediation of childhood neuropsychiatric disease.

Endocannabinoid System Dysregulation from Acetaminophen Use May Lead to Autism Spectrum Disorder: Could Cannabinoid Treatment Be Efficacious?

Persistent deficits in social communication and interaction, and restricted, repetitive patterns of behavior, interests or activities, are the core items characterizing autism spectrum disorder (ASD). Strong inflammation states have been reported to be associated with ASD. The endocannabinoid system (ECS) may be involved in ASD pathophysiology. This complex network of lipid signaling pathways comprises arachidonic acid and 2-arachidonoyl glycerol-derived compounds, their G-protein-coupled receptors (cannabinoid receptors CB1 and CB2) and the associated enzymes. Alterations of the ECS have been reported in both the brain and the immune system of ASD subjects. ASD children show low EC tone as indicated by low blood levels of endocannabinoids. Acetaminophen use has been reported to be associated with an increased risk of ASD. This drug can act through the ECS to produce analgesia. It may be that acetaminophen use in children increases the risk for ASD by interfering with the ECS.This mini-review article summarizes the current knowledge on this topic.

Optimization of the Heterologous Expression of the Cannabinoid Type-1 (CB1) Receptor

The G protein-coupled type 1 cannabinoid receptor (CB₁R) mediates virtually all classic cannabinoid effects, and both its agonists and antagonists hold major therapeutic potential. Heterologous expression of receptors is vital for pharmacological research, however, overexpression of these proteins may fundamentally alter their localization pattern, change the signalling partner preference and may also spark artificial clustering. Additionally, recombinant CB₁Rs are prone to intense proteasomal degradation, which may necessitate substantial modifications, such as N-terminal truncation or signal sequence insertion, for acceptable cell surface expression. We report here that tuning down the expression intensity of the full-length CB₁R reduces proteasomal degradation and offers receptor levels that are comparable to those of endogenous CB₁ receptors. As opposed to high-efficiency expression with conventional promoters, weak promoter-driven CB₁R expression provides ERK 1/2 and p38 MAPK signalling that closely resemble the activity of endogenous CB₁Rs. Moreover, weakly expressed CB₁R variants exhibit plasma membrane localization, preserve canonical G_i-signalling but prevent CB₁R-G_s coupling observed with high-expression variants. Based on these findings, we propose that lowering the expression level of G protein-coupled receptors should always be considered in heterologous expression systems in order to reduce the pressure on the proteasomal machinery and to avoid potential signalling artefacts.

Cannabinoid receptor subtype influence on neuritogenesis in human SH-SY5Y cells

Human SH-SY5Y neuroblastoma cells stably expressing exogenous CB₁ (CB₁XS) or CB₂ (CB₂XS) receptors were developed to investigate endocannabinoid signaling in the extension of neuronal projections. Expression of cannabinoid receptors did not alter proliferation rate, viability, or apoptosis relative to parental SH-SY5Y. Transcripts for endogenous cannabinoid system enzymes (diacylglycerol lipase, monoacylglycerol lipase, α/β-hydrolase domain containing proteins 6 and 12, N-acyl phosphatidylethanolamine-phospholipase D, and fatty acid amide hydrolase) were not altered by CB₁ or CB₂ expression. Endocannabinoid ligands 2-arachidonoylglycerol (2-AG) and anandamide were quantitated in SH-SY5Y cells, and diacylglycerol lipase inhibitor tetrahydrolipstatin decreased 2-AG abundance by 90% but did not alter anandamide abundance. M3 muscarinic agonist oxotremorine M, and inhibitors of monoacylglycerol lipase and α/β hydrolase domain containing proteins 6 &12 increased 2-AG abundance. CB₁ receptor expression increased lengths of short (<30 μm) and long (>30 μm) projections, and this effect was significantly reduced by tetrahydrolipstatin, indicative of stimulation by endogenously produced 2-AG. Pertussis toxin, Gβγ inhibitor gallein, and β-arrestin inhibitor barbadin did not significantly alter long projection length in CB₁XS, but significantly reduced short projections, with gallein having the greatest inhibition. The rho kinase inhibitor Y27632 increased CB₁ receptor-mediated long projection extension, indicative of actin cytoskeleton involvement. CB₁ receptor expression increased GAP43 and ST8SIA2 mRNA and decreased ITGA1 mRNA, whereas CB₂ receptor expression increased NCAM and SYT mRNA. We propose that basal endogenous production of 2-AG provides autocrine stimulation of CB₁ receptor signaling through Gi/o, Gβγ, and β-arrestin mechanisms to promote neuritogenesis, and rho kinase influences process extension.

CB1 Cannabinoid Receptors Stimulate Gβγ-GRK2-Mediated FAK Phosphorylation at Tyrosine 925 to Regulate ERK Activation Involving Neuronal Focal Adhesions

CB₁ cannabinoid receptors (CB₁) are abundantly expressed in the nervous system where they regulate focal adhesion kinase (FAK) and the mitogen-activated protein kinases (MAPK) extracellular signal-regulated kinase 1 and 2 (ERK1/2). However, the role of CB₁-stimulated FAK 925 tyrosine phosphorylation (Tyr-P) in regulating ERK1/2 activation remains undefined. Here, immunoblotting analyses using antibodies against FAK phospho-Tyr 925 and ERK2 phospho-Tyr 204 demonstrated CB₁-stimulated FAK 925 Tyr-P and ERK2 204 Tyr-P (0–5 min) which was followed by a decline in Tyr-P (5–20 min). CB₁ stimulated FAK-Grb2 association and Ras-mediated ERK2 activation. The FAK inhibitors Y11 and PF 573228 abolished FAK 925 Tyr-P and partially inhibited ERK2 204 Tyr-P. FAK 925 Tyr-P and ERK2 204 Tyr-P were adhesion-dependent, required an intact actin cytoskeleton, and were mediated by integrins, Flk-1 vascular endothelial growth factor receptors, and epidermal growth factor receptors. FAK 925 Tyr-P and ERK2 204 Tyr-P were blocked by the Gβγ inhibitor gallein, a GRK2 inhibitor, and GRK2 siRNA silencing, suggesting Gβγ and GRK2 participate in FAK-mediated ERK2 activation. Together, these studies indicate FAK 925 Tyr-P occurs concurrently with CB₁-stimulated ERK2 activation and requires the actin cytoskeleton and G_i/oβγ-GRK2-mediated cross-talk between CB₁, integrins, and receptor tyrosine kinases (RTKs).

Effects of cannabis exposure in the prenatal and adolescent periods: Preclinical and clinical studies in both sexes

Cannabis is the most commonly used illicit drug among adolescents and young adults, including pregnant women. There is substantial evidence for a significant association between prenatal cannabis exposure and lower birth weight in offspring, and mixed results regarding later behavioural outcomes in the offspring. Adolescent cannabis use, especially heavy use, has been associated with altered executive function, depression, psychosis and use of other drugs later in life. Human studies have limitations due to several confounding factors and have provided scarce information about sex differences. In general, animal studies support behavioural alterations reported in humans and have revealed diverse sex differences and potential underlying mechanisms (altered mesolimbic dopaminergic and hippocampal glutamatergic systems and interference with prefrontal cortex maturation). More studies are needed that analyse sex and gender influences on cannabis-induced effects with great clinical relevance such as psychosis, cannabis use disorder and associated comorbidities, to achieve more personalized and accurate treatments.

Δ9-tetrahydrocannabinol and 2-AG decreases neurite outgrowth and differentially affects ERK1/2 and Akt signaling in hiPSC-derived cortical neurons

Endocannabinoids regulate different aspects of neurodevelopment. In utero exposure to the exogenous psychoactive cannabinoid Δ⁹-tetrahydrocannabinol (Δ⁹-THC), has been linked with abnormal cortical development in animal models. However, much less is known about the actions of endocannabinoids in human neurons. Here we investigated the effect of the endocannabinoid 2-arachidonoyl glycerol (2AG) and Δ⁹-THC on the development of neuronal morphology and activation of signaling kinases, in cortical neurons derived from human induced pluripotent stem cells (hiPSCs). Our data indicate that the cannabinoid type 1 receptor (CB1R), but not the cannabinoid 2 receptor (CB2R), GPR55 or TRPV1 receptors, is expressed in young, immature hiPSC-derived cortical neurons. Consistent with previous reports, 2AG and Δ⁹-THC negatively regulated neurite outgrowth. Interestingly, acute exposure to both 2AG and Δ⁹-THC inhibited phosphorylation of serine/threonine kinase extracellular signal-regulated protein kinases (ERK1/2), whereas Δ⁹-THC also reduced phosphorylation of Akt (aka PKB). Moreover, the CB1R inverse agonist SR 141716A attenuated the decrease in neurite outgrowth and ERK1/2 phosphorylation induced by 2AG and Δ⁹-THC. Taken together, our data suggest that hiPSC-derived cortical neurons express CB1Rs and are responsive to exogenous cannabinoids. Thus, hiPSC-neurons may represent a good cellular model for investigating the role of the endocannabinoid system in regulating cellular processes in developing human neurons.

Molecular Mechanism and Cannabinoid Pharmacology

Since antiquity, Cannabis has provoked enormous intrigue for its potential medicinal properties as well as for its unique pharmacological effects. The elucidation of its major cannabinoid constituents, Δ9-tetrahydrocannabinol (THC) and cannabidiol (CBD), led to the synthesis of new cannabinoids (termed synthetic cannabinoids) to understand the mechanisms underlying the pharmacology of Cannabis. These pharmacological tools were instrumental in the ultimate discovery of the endogenous cannabinoid system, which consists of CB1 and CB2 cannabinoid receptors and endogenously produced ligands (endocannabinoids), which bind and activate both cannabinoid receptors. CB1 receptors mediate the cannabimimetic effects of THC and are highly expressed on presynaptic neurons in the nervous system, where they modulate neurotransmitter release. In contrast, CB2 receptors are primarily expressed on immune cells. The endocannabinoids are tightly regulated by biosynthetic and hydrolytic enzymes. Accordingly, the endocannabinoid system plays a modulatory role in many physiological processes, thereby generating many promising therapeutic targets. An unintended consequence of this research was the emergence of synthetic cannabinoids sold for human consumption to circumvent federal laws banning Cannabis use. Here, we describe research that led to the discovery of the endogenous cannabinoid system and show how knowledge of this system benefitted as well as unintentionally harmed human health.

NanoPaint: A Tool for Rapid and Dynamic Imaging of Membrane Structural Plasticity at the Nanoscale

Single-particle tracking with quantum dots (QDs) constitutes a powerful tool to track the nanoscopic dynamics of individual cell membrane components unveiling their membrane diffusion characteristics. Here, the nano-resolved population dynamics of QDs is exploited to reconstruct the topography and structural changes of the cell membrane surface with high temporal and spatial resolution. For this proof-of-concept study, bright, small, and stable biofunctional QD nanoconstructs are utilized recognizing the endogenous neuronal cannabinoid receptor 1, a highly expressed and fast-diffusing membrane protein, together with a commercial point-localization microscope. Rapid QD diffusion on the axonal plasma membrane of cultured hippocampal neurons allows precise reconstruction of the membrane surface in less than 1 min with a spatial resolution of tens of nanometers. Access of the QD nanoconstructs to the synaptic cleft enables rapid 3D topological reconstruction of the entire presynaptic component. Successful reconstruction of membrane nano-topology and deformation at the second time-scale is also demonstrated for HEK293 cell filopodia and axons. Named "nanoPaint," this super-resolution imaging technique amenable to any endogenous transmembrane target represents a versatile platform to rapidly and accurately reconstruct the cell membrane nano-topography, thereby enabling the study of the rapid dynamic phenomena involved in neuronal membrane plasticity.

Cannabinoids: Potential Role in Inflammatory and Neoplastic Skin Diseases

The endocannabinoid system is a complex and nearly ubiquitous network of endogenous ligands, enzymes, and receptors that can also be stimulated by exogenous compounds such as those derived from the marijuana plant, Cannabis sativa. Recent data have shown that the endocannabinoid system is fully functional in the skin and is responsible for maintaining many aspects of skin homeostasis, such as proliferation, differentiation, and release of inflammatory mediators. Because of its role in regulating these key processes, the endocannabinoid system has been studied for its modulating effects on both inflammatory disorders of the skin and skin cancer. Although legal restrictions on marijuana as a Schedule I drug in the USA have made studying cannabinoid compounds unfavorable, an increasing number of studies and clinical trials have focused on the therapeutic uses of cannabinoids. This review seeks to summarize the current, and rapidly expanding field of research on the broad potential uses of cannabinoids in inflammatory and neoplastic diseases of the skin.

Sex Differences in the Behavioral and Synaptic Consequences of a Single in vivo Exposure to the Synthetic Cannabimimetic WIN55,212-2 at Puberty and Adulthood

Heavy cannabis consumption among adolescents is associated with significant and lasting neurobiological, psychological and health consequences that depend on the age of first use. Chronic exposure to cannabinoid agonists during the perinatal period or adolescence alters social behavior and prefrontal cortex (PFC) activity in adult rats. However, sex differences on social behavior as well as PFC synaptic plasticity after acute cannabinoid activation remain poorly explored. Here, we determined that the consequences of a single in vivo exposure to the synthetic cannabimimetic WIN55,212-2 differently affected PFC neuronal and synaptic functions after 24 h in male and female rats during the pubertal and adulthood periods. During puberty, single cannabinoid exposure (SCE) reduced play behavior in females but not males. In contrast, the same treatment impaired sociability in both sexes at adulthood. General exploration and memory recognition remained normal at both ages and both sexes. At the synaptic level, SCE ablated endocannabinoid-mediated synaptic plasticity in the PFC of females of both ages and heightened excitability of PFC pyramidal neurons at adulthood, while males were spared. In contrast, cannabinoid exposure was associated with impaired long-term potentiation (LTP) specifically in adult males. Together, these data indicate behavioral and synaptic sex differences in response to a single in vivo exposure to cannabinoid at puberty and adulthood.

A systematic review of phytocannabinoid exposure on the endocannabinoid system: Implications for psychosis

Cannabis, the most widely used illicit drug worldwide, produces psychoactive effects through its component cannabinoids, which act on the endocannabinoid system. Research on how cannabinoid exposure affects the endocannabinoid system is limited. Substantial evidence indicates cannabis use as a risk factor for psychosis, and the mechanism(s) by which this is occurring is/are currently unknown. Here, we conduct the first review of the effects of exogenous cannabinoids on the endocannabinoid system in humans with and without psychotic disorders. The most well established finding is the down-regulation of cannabinoid CB1 receptors (CB1R) after chronic and recent cannabis exposure, but it remains uncertain whether this effect is present in cannabis users with schizophrenia. We highlight where cannabis exposure affects the endocannabinoid system in a pattern that may mirror what is seen in psychosis, and how further research can push this field forward. In these times of changing cannabis legislation, research highlighting the biological effects of cannabinoids is greatly needed.

A review on neuroimaging studies of genetic and environmental influences on early brain development

The past decades witnessed a surge of interest in neuroimaging study of normal and abnormal early brain development. Structural and functional studies of normal early brain development revealed massive structural maturation as well as sequential, coordinated, and hierarchical emergence of functional networks during the infancy period, providing a great foundation for the investigation of abnormal early brain development mechanisms. Indeed, studies of altered brain development associated with either genetic or environmental risks emerged and thrived. In this paper, we will review selected studies of genetic and environmental risks that have been relatively more extensively investigated-familial risks, candidate risk genes, and genome-wide association studies (GWAS) on the genetic side; maternal mood disorders and prenatal drug exposures on the environmental side. Emerging studies on environment-gene interactions will also be reviewed. Our goal was not to perform an exhaustive review of all studies in the field but to leverage some representative ones to summarize the current state, point out potential limitations, and elicit discussions on important future directions.

Physiology of the Endocannabinoid System During Development

The endocannabinoid (eCB) system comprises endogenously produced cannabinoids (CBs), enzymes of their production and degradation, and CB-sensing receptors and transporters. The eCB system plays a critical role in virtually all stages of animal development. Studies on eCB system components and their physiological role have gained increasing attention with the rising legalization and medical use of marijuana products. The latter represent exogenous interventions that target the eCB system. This chapter summarizes knowledge in the field of CB contribution to gametogenesis, fertilization, embryo implantation, fetal development, birth, and adolescence-equivalent periods of ontogenesis. The material is complemented by the overview of data from our laboratory documenting the functional presence of the eCB system within cerebral arteries of baboons at different stages of development.

Exposure to cannabinoid agonist WIN 55,212-2 during early adolescence increases alcohol preference and anxiety in CD1 mice

The endocannabinoid (eCB) system is involved in the modulation of the reward system and participates in the reinforcing effects of different drugs of abuse, including alcohol. The most abundant receptor of the eCB system in the central nervous system is the CB1 receptor (CB1R), which is predominantly expressed in areas involved in drug addiction, such as the nucleus accumbens, the ventral tegmental area, the substantia nigra and the raphe nucleus. CB1R is expressed in early stages during development, and reaches maximum levels during early adolescence. In addition, cannabinoid receptor 2 has been found expressed also in the central nervous system at postsynaptic level. In order to analyze the participation of the eCB system on ethanol (EtOH) preference, mice were exposed to cannabinoid agonist WIN 55,212-2 (WIN) for 5 consecutive days during early adolescence. Anxiety tests were performed the day after WIN treatment withdrawal, and EtOH preference was measured throughout adolescence. Mice exposed to WIN during early adolescence exhibited a significant increase in EtOH intake and preference after treatment. Moreover, WIN exposure during early adolescence induced an anxiogenic effect. Morphometric analysis revealed higher dendritic ramifications and fewer dendritic spines in neurons of the substantia nigra pars compacta in WIN-treated mice. On the other hand, immunohistochemical analysis revealed an increase in the number of tryptophan hydroxylase-expressing neurons in the dorsal raphe nucleus but no differences were found in the ventral tegmental area or substantia nigra pars compacta for tyrosine hydroxylase-expressing neurons. These results demonstrate that exposure to WIN in early adolescence can affect neural development and induce alcohol preference and anxiety-like behavior during late adolescence.

The Endocannabinoid System across Postnatal Development in Transmembrane Domain Neuregulin 1 Mutant Mice

The use of cannabis is a well-established component risk factor for schizophrenia, particularly in adolescent individuals with genetic predisposition for the disorder. Alterations to the endocannabinoid system have been found in the prefrontal cortex of patients with schizophrenia. Thus, we assessed whether molecular alterations exist in the endocannabinoid signalling pathway during brain development in a mouse model for the schizophrenia risk gene neuregulin 1 (Nrg1). We analysed transcripts encoding key molecules of the endocannabinoid system in heterozygous transmembrane domain Nrg1 mutant mice (Nrg1 TM HET), which is known to have increased sensitivity to cannabis exposure. Tissue from the prelimbic cortex and hippocampus of male and female Nrg1 TM HET mice and wild type-like littermates was collected at postnatal days (PNDs) 7, 10, 14, 21, 28, 35, 49, and 161. Quantitative polymerase chain reaction was conducted to assess mRNA levels of cannabinoid receptor 1 (CB₁R) and enzymes for the synthesis and breakdown of the endocannabinoid 2-arachidonoylglycerol [i.e., diacylglycerol lipase alpha (DAGLα), monoglyceride lipase (MGLL), and α/β-hydrolase domain-containing 6 (ABHD6)]. No sex differences were found for any transcripts in either brain region; thus, male and female data were pooled. Hippocampal and cortical mRNA expression of DAGLα, MGLL, and ABHD6 increased until PND 21-35 and then decreased and stabilised for the rest of postnatal development. Hippocampal CB₁R mRNA expression increased until PND 21 and decreased after this age. Expression levels of these endocannabinoid markers did not differ in Nrg1 TM HET compared to control mice at any time point. Here, we demonstrate dynamic changes in the developmental trajectory of several key endocannabinoid system transcripts in the mouse brain, which may correspond with periods of endocannabinoid system maturation. Nrg1 TM HET mutation did not alter the developmental trajectory of the endocannabinoid markers assessed, suggesting that other mechanisms may be responsible for the exaggerated cannabinoid susceptibility in these mice.

Marijuana Use and Organ Transplantation: a Review and Implications for Clinical Practice

PURPOSE OF REVIEW

Physicians of all disciplines must rapidly adjust their clinical practices following the expansion of marijuana legalization across the country. Organ transplantation teams are uniquely struggling in this gray zone with eight states having passed laws explicitly banning the denial of transplant listing based on a patient's use of medical marijuana. In this review, we examine the clinical evidence of marijuana use in transplant patients to enable psychiatric providers to meaningfully contribute to the relevant medical and psychiatric aspects of this issue in a unique patient population.

RECENT FINDINGS

There is no consensus among experts regarding marijuana use in transplantation patients. There are extant case reports of post-transplant complications attributed to marijuana use including membranous glomerulonephritis, ventricular tachycardia, and tacrolimus toxicity. However, recent studies suggest that the overall survival rates in kidney, liver, lung, and heart transplant patients using marijuana are equivalent to non-users. Transplant teams should not de facto exclude marijuana users from transplant listing but instead holistically evaluate a patient's candidacy, integrating meaningful medical, psychiatric, and social variables into the complex decision-making process. Psychiatric providers can play a key role in this process. Appropriate stewardship over donor organs, a limited and precious resource, will require a balance of high-clinical standards with inclusive efforts to treat as many patients as possible.

Chronic CB1 cannabinoid receptor antagonism persistently increases dendritic spine densities in brain regions important to zebra finch vocal learning and production in an antidepressant-sensitive manner

During typical late-postnatal CNS development, net reductions in dendritic spine densities are associated with activity-dependent learning. Prior results showed agonist exposure in young animals increased spine densities in a subset of song regions while adult exposures did not, suggesting endocannabinoid signaling regulates dendritic spine dynamics important to vocal development. Here we addressed this question using the CB1 receptor-selective antagonist SR141716A (SR) to disrupt endocannabinoid signaling both during and after vocal learning. We hypothesized antagonist exposure during vocal development, but not adulthood, would alter spine densities. Following 25days of exposure and a 25day maturation period, 3D reconstructions of Golgi-Cox stained neurons were used to measure spine densities. We found antagonist treatments during both age periods increased densities within Area X (basal ganglia) and following adult treatments within HVC (premotor cortical-like). Results suggest both inappropriate cannabinoid receptor stimulation and inhibition are capable of similar disregulatory effects during establishment of circuits important to vocal learning, with antagonism extending these effects through adulthood. Given clinical evidence of depressant effects of SR, we tested the ability of the antidepressant monoamine oxidase inhibitor (MAOI) phenelzine to mitigate SR-induced spine density increases. This was confirmed implicating interaction between monoamine and endocannabinoid systems. Finally, we evaluated acute effects of these drugs to alter ability of novel song exposure to increase spine densities in auditory NCM and other regions, finding when combined, SR and phenelzine increased densities within Area X. These results contribute to understanding relevance of dendritic spine dynamics in neuronal development, drug abuse, and depression.

CB1 and CB2 Receptor Pharmacology

The CB1 and CB2 cannabinoid receptors (CB1R, CB2R) are members of the G protein-coupled receptor (GPCR) family that were identified over 20 years ago. CB1Rs and CB2Rs mediate the effects of Δ9-tetrahydrocannabinol (Δ9-THC), the principal psychoactive constituent of marijuana, and subsequently identified endogenous cannabinoids (endocannabinoids) anandamide and 2-arachidonoyl glycerol. CB1Rs and CB2Rs have both similarities and differences in their pharmacology. Both receptors recognize multiple classes of agonist and antagonist compounds and produce an array of distinct downstream effects. Natural polymorphisms and alternative splice variants may also contribute to their pharmacological diversity. As our knowledge of the distinct differences grows, we may be able to target select receptor conformations and their corresponding pharmacological responses. This chapter will discuss their pharmacological characterization, distribution, phylogeny, and signaling pathways. In addition, the effects of extended agonist exposure and how that affects signaling and expression patterns of the receptors are considered.

Cannabinoid Receptors Modulate Neuronal Morphology and AnkyrinG Density at the Axon Initial Segment

Neuronal polarization underlies the ability of neurons to integrate and transmit information. This process begins early in development with axon outgrowth, followed by dendritic growth and subsequent maturation. In between these two steps, the axon initial segment (AIS), a subcellular domain crucial for generating action potentials (APs) and maintaining the morphological and functional polarization, starts to develop. However, the cellular/molecular mechanisms and receptors involved in AIS initial development and maturation are mostly unknown. In this study, we have focused on the role of the type-1 cannabinoid receptor (CB1R), a highly abundant G-protein coupled receptor (GPCR) in the nervous system largely involved in different phases of neuronal development and differentiation. Although CB1R activity modulation has been related to changes in axons or dendrites, its possible role as a modulator of AIS development has not been yet explored. Here we analyzed the potential role of CB1R on neuronal morphology and AIS development using pharmacological and RNA interference approaches in cultured hippocampal neurons. CB1R inhibition, at a very early developmental stage, has no effect on axonal growth, yet CB1R activation can promote it. By contrast, subsequent dendritic growth is impaired by CB1R inhibition, which also reduces ankyrinG density at the AIS. Moreover, our data show a significant correlation between early dendritic growth and ankyrinG density. However, CB1R inhibition in later developmental stages after dendrites are formed only reduces ankyrinG accumulation at the AIS. In conclusion, our data suggest that neuronal CB1R basal activity plays a role in initial development of dendrites and indirectly in AIS proteins accumulation. Based on the lack of CB1R expression at the AIS, we hypothesize that CB1R mediated modulation of dendritic arbor size during early development indirectly determines the accumulation of ankyrinG and AIS development. Further studies will be necessary to determine which CB1R-dependent mechanisms can coordinate these two domains, and what may be the impact of these early developmental changes once neurons mature and are embedded in a functional brain network.

Sexually-dimorphic alterations in cannabinoid receptor density depend upon prenatal/early postnatal history

Recent research has demonstrated that the endogenous cannabinoid system is central to the brain's response to stress. As part of an ongoing collaboration, we sought to examine the effects of prenatal and early postnatal rearing and housing conditions on developing endocannabinoid systems. We compare brain cannabinoid receptors (CBR) in offspring of either prenatal vehicle intubated or non-treated dams (Experiment 1) or in rats derived from a vendor and shipped at weaning to a collaborating lab (Experiment 2). From postnatal day (PND) 23, all rats were either housed in isolated conditions or enriched conditions with 3 rats/cage and a variety of stimulus objects changed twice a week. All rats underwent 5days of handling as controls for a behavior study and all rats were sacrificed at approximately PND48-50 within 2hours of the last behavioral test. All brains were processed together for CB1 receptor binding using ³H CP55,940 in prefrontal cortex, striatum, amygdala and hippocampus. Conditions in the two labs were as similar as possible since the two studies were intentionally designed to be comparable and contemporary. Results show that 1) comparing offspring of non-treated dams to offspring of dams receiving daily vehicle intubations, males show decreased CB1 binding in most brain regions while females only showed alterations in the hippocampus and these were increases in the offspring of the vehicle-intubated dams. 2) When comparing offspring of non-treated dams in NY with those derived from a vendor, shipped and maintained in the collaborating lab, this latter group showed reduced CB1 binding in prefrontal cortex in males and increased binding in all four brain regions in females. Therefore, overall, both prenatal handling (intubations) and being vendor-derived, shipped and maintained in a collaborating facility reduced CB1 receptors in males and increased them in females in key limbic brain regions. Effects of environmental enrichment or isolation were minor with only the prefrontal cortex showing an increase in binding in the isolated animals that were offspring of the vehicle-intubated dams. These results support the ideas that prenatal/early postnatal conditions produce different effects in males and females and override the effects of enrichment/isolation on cannabinoid receptors. Behavioral responses to cannabinoid challenges would therefore be expected to vary depending on sex, prenatal/early postnatal history and postweaning conditions of the rats. Since exogenous cannabinoids act through the CBR, the present data may provide a molecular basis for discrepant behavioral effects reported across various labs in the literature as well as sex differences seen following stress and/or manipulation of the cannabinoid system.

Prenatal cannabis exposure - The "first hit" to the endocannabinoid system

As more states and countries legalize medical and/or adult recreational marijuana use, the incidences of prenatal cannabis exposure (PCE) will likely increase. While young people increasingly view marijuana as innocuous, marijuana preparations have been growing in potency in recent years, potentially creating global clinical, public health, and workforce concerns. Unlike fetal alcohol spectrum disorder, there is no phenotypic syndrome associated with PCE. There is also no preponderance of evidence that PCE causes lifelong cognitive, behavioral, or functional abnormalities, and/or susceptibility to subsequent addiction. However, there is compelling circumstantial evidence, based on the principles of teratology and fetal malprogramming, suggesting that pregnant women should refrain from smoking marijuana. The usage of marijuana during pregnancy perturbs the fetal endogenous cannabinoid signaling system (ECSS), which is present and active from the early embryonic stage, modulating neurodevelopment and continuing this role into adulthood. The ECSS is present in virtually every brain structure and organ system, and there is also evidence that this system is important in the regulation of cardiovascular processes. Endocannabinoids (eCBs) undergird a broad spectrum of processes, including the early stages of fetal neurodevelopment and uterine implantation. Delta-9-tetrahydrocannabinol (THC), the psychoactive chemical in cannabis, enters maternal circulation, and readily crosses the placental membrane. THC binds to CB receptors of the fetal ECSS, altering neurodevelopment and possibly rewiring ECSS circuitry. In this review, we discuss the Double-Hit Hypothesis as it relates to PCE. We contend that PCE, similar to a neurodevelopmental teratogen, delivers the first hit to the ECSS, which is compromised in such a way that a second hit (i.e., postnatal stressors) will precipitate the emergence of a specific phenotype. In summary, we conclude that perturbations of the intrauterine milieu via the introduction of exogenous CBs alter the fetal ECSS, predisposing the offspring to abnormalities in cognition and altered emotionality. Based on recent experimental evidence that we will review here, we argue that young women who become pregnant should immediately take a "pregnant pause" from using marijuana.

Functional Connectivity of the Infant Human Brain: Plastic and Modifiable

Infancy is a critical and immensely important period in human brain development. Subtle changes during this stage may be greatly amplified with the unfolding of different developmental processes, exerting far-reaching consequences. Studies of the structure and behavioral manifestations of the infant brain are fruitful. However, the specific functional brain mechanisms that enable the execution of different behaviors remained elusive until the advent of functional connectivity fMRI (fcMRI), which provides an unprecedented opportunity to probe the infant functional brain development in vivo. Since its inception, a burgeoning field of infant brain functional connectivity study has emerged and thrived during the past decade. In this review, we describe (1) findings of normal development of functional connectivity networks and their relationships to behaviors and (2) disruptions of the normative functional connectivity development due to identifiable genetic and/or environmental risk factors during the first 2 years of human life. Technical considerations of infant fcMRI are also provided. It is our hope to consolidate previous findings so that the field can move forward with a clearer picture toward the ultimate goal of fcMRI-based objective methods for early diagnosis/identification of risks and evaluation of early interventions to optimize developing functional connectivity networks in this critical developmental window.

Intrathecal Injection of JWH-015 Attenuates Bone Cancer Pain Via Time-Dependent Modification of Pro-inflammatory Cytokines Expression and Astrocytes Activity in Spinal Cord

Cannabinoid receptor type 2 (CB2) agonists display potential analgesic effects in acute and neuropathic pain. However, its complex cellular and molecular mechanisms in bone cancer pain remain unclear. And less relevant reports concerned its time-dependent effects on the long-lasting modifications of behavior, spinal inflammatory cytokines levels, astrocytes activity induced by bone cancer pain. A rat model of bone cancer pain induced by intra-tibia inoculation of Walker 256 mammary gland carcinoma cells was utilized. Pain behaviors at different time points were assessed by ambulatory pain scores and paw withdrawal mechanical threshold (PWMT). Pro-inflammatory cytokines, such as interleukin (IL)-1β, IL-6, IL-18, and tumor necrosis factor alpha (TNF-α), were quantitated by Western blots. Glial activity was assessed by immunohistochemistry. Intra-tibia inoculation of Walker 256 mammary gland carcinoma cells induced progressive bone cancer pain; a long-term up-regulation of IL-1β, IL-6, IL-18, and TNF-α; and the activation of glia in spinal cord. Activation of microglia was first evident on day 4 after surgery and reached to a peak on day 7 while activation of astrocytes was on day 10. A single intrathecal injection of JWH-015 attenuated bone cancer induced spontaneous pain and mechanical allodynia, reduced the expression of pro-inflammatory cytokines, and inhibited the activity of astrocytes. All the modifications were transient and peaked at 24 h after JWH-015 administration. Furthermore, the protective effects of JWH-015 were reversed in the presence of CB2-selective antagonist AM630. Overall, our results provided evidences for the persistent participation of inflammation reaction in the progression of bone cancer pain, and demonstrated that JWH-015 reduced the expression of IL-1β, IL-6, IL-18, and TNF-α and inhibited astrocytes activation in a time-dependent manner, thereby displaying an analgesic effect.

Developmental pathways from prenatal marijuana exposure to Cannabis Use Disorder in young adulthood

BACKGROUND

Earlier studies reported an association between prenatal marijuana exposure (PME) and cognitive and behavioral problems in the offspring. A recent publication demonstrated the relation between PME and offspring marijuana use at age 22. There are no reports of the association between PME and Cannabis Use Disorder (CUD) at 22years, the age when use of marijuana and CUD peak.

METHODS

Subjects are from the Maternal Health Practices and Child Development Study, a longitudinal study of PME and other exposures during pregnancy. The cohort of mothers and their offspring has been followed since the fourth prenatal month through 22years of age. A path analysis was conducted on 590 mother-child pairs, representing 77% of the birth cohort, to examine potential pathways from PME to CUD in offspring at 22years of age.

RESULTS

There is no direct effect of PME on CUD. There are, however, two indirect pathways from PME to CUD. In the first, the pathway from PME to CUD goes through offspring early age of marijuana onset. In the second, offspring depression at age 10 and early age of marijuana onset predict CUD.

CONCLUSIONS

Although there is no direct effect of PME on CUD, there are significant indirect pathways from PME to CUD that affect the rate of CUD in the population. Thus, PME, offspring depression, and an early age of marijuana initiation, are significant points for intervention. As marijuana is legalized in more states, the rates of marijuana use will increase significantly, including during pregnancy, and the consequences of the association between PME and CUD will become even more significant from a public health perspective.

Sex and age specific effects of delta-9-tetrahydrocannabinol during the periadolescent period in the rat: The unique susceptibility of the prepubescent animal

Adolescents who use marijuana are more likely to exhibit anxiety, depression, and other mood disorders, including psychotic-like symptoms. Additionally, the age at onset of use and the stress history of the individual can affect responses to cannabis. To examine the effect of early life experience on adolescent Δ-9-tetrahydrocannabinol (THC) exposure, we exposed adolescent (postnatal day (P) 29-38) male and female rats, either shipped from a supplier or born in our vivarium, to once daily injections of 3mg/kg THC. Our findings suggest that males are more sensitive to the anxiolytic and antidepressant effects of THC, as measured by the elevated plus maze (EPM) and forced swim test (FST), respectively, than females. Exposure to the FST increased plasma corticosterone levels, regardless of drug treatment or origin and females had higher levels than males overall. Shipping increased THC responses in females (acoustic startle habituation) and in males (latency to immobility in FST). No significant effects of THC or shipping on pre-pulse inhibition were observed. Due to differences in timing of puberty in males and females during the P29-38 period of THC treatment, we also dosed female rats between P21-30 (pre-puberty) and male rats between P39-48 (puberty). Pre-pubertal animals showed reductions in anxiety on the EPM, an effect that was not seen in animals treated during puberty. These results suggest that both sexes are more susceptible to changes in emotional behavior when THC exposure occurs just prior to the onset of puberty. Within the animals dosed from P29-38, THC increased cannabinoid receptor 1 (CB1R) mRNA expression and tended to decrease CP55,940 stimulated [³⁵S]GTPγS binding in the central amygdala only of females. Therefore, early stress enhances THC responses in males (in FST) and females (ASR habituation), THC alters CB1R expression and function in females only and prepubescent rats are generally more responsive to THC than pubertal rats. In summary, THC and stress interact with the developing endocannabinoid system in a sex specific manner during the peri-pubertal period.

Cannabinoid CB1 receptor inhibition blunts adolescent-typical increased binge alcohol and sucrose consumption in male C57BL/6J mice

Increased binge alcohol consumption has been reported among adolescents as compared to adults in both humans and rodent models, and has been associated with serious long-term health consequences. However, the neurochemical mechanism for age differences in binge drinking between adolescents and adults has not been established. The present study was designed to evaluate the mechanistic role of the cannabinoid CB1 receptor in adolescent and adult binge drinking. Binge consumption was established in adolescent and adult male C57BL/6J mice by providing access to 20% alcohol or 1% sucrose for 4h every other day. Pretreatment with the CB1 antagonist/inverse agonist AM-251 (0, 1, 3, and 10mg/kg) in a Latin square design dose-dependently reduced adolescent alcohol consumption to adult levels without altering adult intake. AM-251 (3mg/kg) also reduced adolescent but not adult sucrose consumption. Adolescent reductions in alcohol and sucrose were not associated with alterations in open-field locomotor activity or thigmotaxis. These findings point to age differences in CB1 receptor activity as a functional mediator of adolescent-typical increased binge drinking as compared to adults. Developmental alterations in endocannabinoid signaling in the adolescent brain may therefore be responsible for the drinking phenotype seen in this age group.

Oriented Bioconjugation of Unmodified Antibodies to Quantum Dots Capped with Copolymeric Ligands as Versatile Cellular Imaging Tools

Distinctive optical properties of inorganic quantum dot (QD) nanoparticles promise highly valuable probes for fluorescence-based detection methods, particularly for in vivo diagnostics, cell phenotyping via multiple markers or single molecule tracking. However, despite high hopes, this promise has not been fully realized yet, mainly due to difficulties at producing stable, nontoxic QD bioconjugates of negligible nonspecific binding. Here, a universal platform for antibody binding to QDs is presented that builds upon the controlled functionalization of CdSe/CdS/ZnS nanoparticles capped with a multidentate dithiol/zwitterion copolymer ligand. In a change-of-paradigm approach, thiol groups are concomitantly used as anchoring and bioconjugation units to covalently bind up to 10 protein A molecules per QD while preserving their long-term colloidal stability. Protein A conjugated to QDs then enables the oriented, stoichiometrically controlled immobilization of whole, unmodified antibodies by simple incubation. This QD-protein A immobilization platform displays remarkable antibody functionality retention after binding, usually a compromised property in antibody conjugation to surfaces. Typical QD-protein A-antibody assemblies contain about three fully functional antibodies. Validation experiments show that these nanobioconjugates overcome current limitations since they retain their colloidal stability and antibody functionality over 6 months, exhibit low nonspecific interactions with live cells and have very low toxicity: after 48 h incubation with 1 μM QD bioconjugates, HeLa cells retain more than 80% of their cellular metabolism. Finally, these QD nanobioconjugates possess a high specificity for extra- and intracellular targets in live and fixed cells. The dithiol/zwitterion QD-protein A nanoconjugates have thus a latent potential to become an off-the-shelf tool destined to unresolved biological questions.

Functional Connectivity Disruption in Neonates with Prenatal Marijuana Exposure

Prenatal marijuana exposure (PME) is linked to neurobehavioral and cognitive impairments; however, findings in childhood and adolescence are inconsistent. Type-1 cannabinoid receptors (CB1R) modulate fetal neurodevelopment, mediating PME effects on growth of functional circuitry sub-serving behaviors critical for academic and social success. The purpose of this study was to investigate the effects of prenatal marijuana on development of early brain functional circuitry prior to prolonged postnatal environmental influences. We measured resting state functional connectivity during unsedated sleep in infants at 2–6 weeks (+MJ: 20 with PME in combination with nicotine, alcohol, opiates, and/or selective serotonin reuptake inhibitors; −MJ: 23 exposed to the same other drugs without marijuana, CTR: 20 drug-free controls). Connectivity of subcortical seed regions with high fetal CB1R expression was examined. Marijuana-specific differences were observed in insula and three striatal connections: anterior insula–cerebellum, right caudate–cerebellum, right caudate–right fusiform gyrus/inferior occipital, left caudate–cerebellum. +MJ neonates had hypo-connectivity in all clusters compared with −MJ and CTR groups. Altered striatal connectivity to areas involved in visual spatial and motor learning, attention, and in fine-tuning of motor outputs involved in movement and language production may contribute to neurobehavioral deficits reported in this at-risk group. Disrupted anterior insula connectivity may contribute to altered integration of interoceptive signals with salience estimates, motivation, decision-making, and later drug use. Compared with CTRs, both +MJ and −MJ groups demonstrated hyper-connectivity of left amygdala seed with orbital frontal cortex and hypo-connectivity of posterior thalamus seed with hippocampus, suggesting vulnerability to multiple drugs in these circuits.

New horizons for newborn brain protection: enhancing endogenous neuroprotection

Intrapartum-related events are the third leading cause of childhood mortality worldwide and result in one million neurodisabled survivors each year. Infants exposed to a perinatal insult typically present with neonatal encephalopathy (NE). The contribution of pure hypoxia-ischaemia (HI) to NE has been debated; over the last decade, the sensitising effect of inflammation in the aetiology of NE and neurodisability is recognised. Therapeutic hypothermia is standard care for NE in high-income countries; however, its benefit in encephalopathic babies with sepsis or in those born following chorioamnionitis is unclear. It is now recognised that the phases of brain injury extend into a tertiary phase, which lasts for weeks to years after the initial insult and opens up new possibilities for therapy.There has been a recent focus on understanding endogenous neuroprotection and how to boost it or to supplement its effectors therapeutically once damage to the brain has occurred as in NE. In this review, we focus on strategies that can augment the body's own endogenous neuroprotection. We discuss in particular remote ischaemic postconditioning whereby endogenous brain tolerance can be activated through hypoxia/reperfusion stimuli started immediately after the index hypoxic-ischaemic insult. Therapeutic hypothermia, melatonin, erythropoietin and cannabinoids are examples of ways we can supplement the endogenous response to HI to obtain its full neuroprotective potential. Achieving the correct balance of interventions at the correct time in relation to the nature and stage of injury will be a significant challenge in the next decade.

Endogenous vs Exogenous Allosteric Modulators in GPCRs: A dispute for shuttling CB1 among different membrane microenvironments

A Cannabinoid Receptor 1 (CB₁) binding site for the selective allosteric modulator ORG27569 is here identified through an integrate approach of consensus pocket prediction, mutagenesis studies and Mass Spectrometry. This unprecedented ORG27569 pocket presents the structural features of a Cholesterol Consensus Motif, a cholesterol interacting region already found in other GPCRs. ORG27569 and cholesterol affects oppositely CB₁ affinity for orthosteric ligands. Moreover, the rise in cholesterol intracellular level results in CB₁ trafficking to the axonal region of neuronal cells, while, on the contrary, ORG27568 binding induces CB₁ enrichment at the soma. This control of receptor migration among functionally different membrane regions of the cell further contributes to downstream signalling and adds a previously unknown mechanism underpinning CB₁ modulation by ORG27569 , that goes beyond a mere control of receptor affinity for orthosteric ligands.