Endocannabinoid signaling in social functioning: an RDoC perspective.

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“Core deficits in social functioning are associated with various neuropsychiatric and neurodevelopmental disorders, yet biomarker identification and the development of effective pharmacological interventions has been limited.

Recent data suggest the intriguing possibility that endogenous cannabinoids, a class of lipid neuromodulators generally implicated in the regulation of neurotransmitter release, may contribute to species-typical social functioning.

Systematic study of the endogenous cannabinoid signaling could, therefore, yield novel approaches to understand the neurobiological underpinnings of atypical social functioning.

This article provides a critical review of the major components of the endogenous cannabinoid system (for example, primary receptors and effectors-Δ9-tetrahydrocannabinol, cannabidiol, anandamide and 2-arachidonoylglycerol) and the contributions of cannabinoid signaling to social functioning.

Data are evaluated in the context of Research Domain Criteria constructs (for example, anxiety, chronic stress, reward learning, motivation, declarative and working memory, affiliation and attachment, and social communication) to enable interrogation of endogenous cannabinoid signaling in social functioning across diagnostic categories.

The empirical evidence reviewed strongly supports the role for dysregulated cannabinoid signaling in the pathophysiology of social functioning deficits observed in brain disorders, such as autism spectrum disorder, schizophrenia, major depressive disorder, posttraumatic stress disorder and bipolar disorder.

Moreover, these findings indicate that the endogenous cannabinoid system holds exceptional promise as a biological marker of, and potential treatment target for, neuropsychiatric and neurodevelopmental disorders characterized by impairments in social functioning.”

https://www.ncbi.nlm.nih.gov/pubmed/27676446

Cannabidiol, among Other Cannabinoid Drugs, Modulates Prepulse Inhibition of Startle in the SHR Animal Model: Implications for Schizophrenia Pharmacotherapy.

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“Schizophrenia is a severe psychiatric disorder that involves positive, negative and cognitive symptoms. Prepulse inhibition of startle reflex (PPI) is a paradigm that assesses the sensorimotor gating functioning and is impaired in schizophrenia patients as well as in animal models of this disorder. Recent data point to the participation of the endocannabinoid system in the pathophysiology and pharmacotherapy of schizophrenia. Here, we focus on the effects of cannabinoid drugs on the PPI deficit of animal models of schizophrenia, with greater focus on the SHR (Spontaneously Hypertensive Rats) strain, and on the future prospects resulting from these findings.”

Cannabinoids: Glutamatergic Transmission and Kynurenines.

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“The endocannabinoid system (ECS) comprises a complex of receptors, enzymes, and endogenous agonists that are widely distributed in the central nervous system of mammals and participates in a considerable number of neuromodulatory functions, including neurotransmission, immunological control, and cell signaling. In turn, the kynurenine pathway (KP) is the most relevant metabolic route for tryptophan degradation to form the metabolic precursor NAD(+).

Recent studies demonstrate that the control exerted by the pharmacological manipulation of the ECS on the glutamatergic system in the brain may offer key information not only on the development of psychiatric disorders like psychosis and schizophrenia-like symptoms, but it also may constitute a solid basis for the development of therapeutic strategies to combat excitotoxic events occurring in neurological disorders like Huntington’s disease (HD).

Part of the evidence pointing to the last approach is based on experimental protocols demonstrating the efficacy of cannabinoids to prevent the deleterious actions of the endogenous neurotoxin and KP metabolite quinolinic acid (QUIN).

These findings intuitively raise the question about what is the precise role of the ECS in tryptophan metabolism through KP and vice versa. In this chapter, we will review basic concepts on the physiology of both the ECS and the KP to finally describe those recent findings combining the components of these two systems and hypothesize the future course that the research in this emerging field will take in the next years.”

Cannabinoid Agonists Show Promise for Anorexia

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“Impairments in the endocannabinoid system in the brain could play an important role in the development of anorexia nervosa, say Italian researchers, who report findings that point to novel cannabis-based therapeutic strategies for the eating disorder.

In a mouse model of anorexia, the team found not only that the density of cannabinoid receptors was significantly reduced in areas associated with appetite but also that administration of receptor agonists led to increases in body weight and a reduction in interest in exercise.”

http://www.medscape.com/viewarticle/868990

Δ9-Tetrahydrocannabinol Reverses TNFα-induced Increase in Airway Epithelial Cell Permeability through CB2 Receptors.

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“Despite pharmacological treatment, bronchial hyperresponsiveness continues to deteriorate as airway remodelling persists in airway inflammation.

Previous studies have demonstrated that the phytocannabinoid Δ9-tetrahydrocannabinol (THC) reverses bronchoconstriction with an anti-inflammatory action.

The aim of this study was to investigate the effects of THC on bronchial epithelial cell permeability after exposure to the pro-inflammatory cytokine, TNFα. Calu-3 bronchial epithelial cells were cultured at air-liquid interface.

These data indicate that THC prevents cytokine-induced increase in airway epithelial permeability through CB2 receptor activation.

This highlights that THC, or other cannabinoid receptor ligands, could be beneficial in the prevention of inflammation-induced changes in airway epithelial cell permeability, an important feature of airways diseases.”

http://www.ncbi.nlm.nih.gov/pubmed/27641813

The endocannabinoid anandamide causes endothelium-dependent vasorelaxation in human mesenteric arteries.

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“The endocannabinoid anandamide (AEA) causes vasorelaxation in animal studies.

Although circulating AEA levels are increased in many pathologies, little is known about its vascular effects in humans. The aim of this work was to characterise the effects of AEA in human arteries.

Post hoc analysis of the data set showed that overweight patients and those taking paracetamol had reduced vasorelaxant responses to AEA.

These data show that AEA causes moderate endothelium-dependent, NO-dependent vasorelaxation in human mesenteric arteries via activation of CB1 receptors.”

http://www.ncbi.nlm.nih.gov/pubmed/27633407

From Phytocannabinoids to Cannabinoid Receptors and Endocannabinoids: Pleiotropic Physiological and Pathological Roles Through Complex Pharmacology.

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“Apart from having been used and misused for at least four millennia for, among others, recreational and medicinal purposes, the cannabis plant and its most peculiar chemical components, the plant cannabinoids (phytocannabinoids), have the merit to have led humanity to discover one of the most intriguing and pleiotropic endogenous signaling systems, the endocannabinoid system (ECS).

This review article aims to describe and critically discuss, in the most comprehensive possible manner, the multifaceted aspects of 1) the pharmacology and potential impact on mammalian physiology of all major phytocannabinoids, and not only of the most famous one Δ9-tetrahydrocannabinol, and 2) the adaptive pro-homeostatic physiological, or maladaptive pathological, roles of the ECS in mammalian cells, tissues, and organs.

In doing so, we have respected the chronological order of the milestones of the millennial route from medicinal/recreational cannabis to the ECS and beyond, as it is now clear that some of the early steps in this long path, which were originally neglected, are becoming important again. The emerging picture is rather complex, but still supports the belief that more important discoveries on human physiology, and new therapies, might come in the future from new knowledge in this field.”

http://www.ncbi.nlm.nih.gov/pubmed/27630175

Important role of endocannabinoid signaling in the development of functional vision and locomotion in zebrafish.

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“The developmental role of the endocannabinoid system still remains to be fully understood.

Here, we report the presence of a complete endocannabinoid system during zebrafish development and show that the genes that code for enzymes that catalyze the anabolism and catabolism (mgll and dagla) of the endocannabinoid, 2-AG (2-arachidonoylglycerol), as well as 2-AG main receptor in the brain, cannabinoid receptor type 1, are coexpressed in defined regions of axonal growth.

By using morpholino-induced transient knockdown of the zebrafish Daglα homolog and its pharmacologic rescue, we suggest that synthesis of 2-AG is implicated in the control of axon formation in the midbrain-hindbrain region and that animals that lack Daglα display abnormal physiological behaviors in tests that measure stereotyped movement and motion perception.

Our results suggest that the well-established role for 2-AG in axonal outgrowth has implications for the control of vision and movement in zebrafish and, thus, is likely common to all vertebrates.”

http://www.ncbi.nlm.nih.gov/pubmed/27623930

Oleoylethanolamine and palmitoylethanolamine modulate intestinal permeability in vitro via TRPV1 and PPARα.

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“Cannabinoids modulate intestinal permeability through CB1.

The endocannabinoid-like compounds oleoylethanolamine (OEA) and palmitoylethanolamine (PEA) play an important role in digestive regulation, and we hypothesized they would also modulate intestinal permeability.

OEA and PEA have endogenous roles and potential therapeutic applications in conditions of intestinal hyperpermeability and inflammation.”

http://www.ncbi.nlm.nih.gov/pubmed/27623929

Don’t Worry, Be Happy: Endocannabinoids and Cannabis at the Intersection of Stress and Reward.

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“Cannabis enables and enhances the subjective sense of well-being by stimulating the endocannabinoid system (ECS), which plays a key role in modulating the response to stress, reward, and their interactions.

The recent shift toward legalization of medical or recreational cannabis has renewed interest in investigating the physiological role of the ECS as well as the potential health effects, both adverse and beneficial, of cannabis.

Here we review our current understanding of the ECS and its complex physiological roles.

We discuss the implications of this understanding vis-á-vis the ECS’s modulation of stress and reward and its relevance to mental disorders in which these processes are disrupted (i.e., addiction, depression, posttraumatic stress disorder, schizophrenia), along with the therapeutic potential of strategies to manipulate the ECS for these conditions.”

http://www.ncbi.nlm.nih.gov/pubmed/27618739