Integrating endocannabinoid signaling in the regulation of anxiety and depression

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“Brain endogenous cannabinoid (eCB) signaling seems to harmonize appropriate behavioral responses, which are essential for the organism’s long-term viability and homeostasis. Dysregulation of eCB signaling contributes to negative emotional states and increased stress responses. An understanding of the underlying neural cell populations and neural circuit regulation will enable the development of therapeutic strategies to mitigate behavioral maladaptation and provide insight into the influence of eCB on the neural circuits involved in anxiety and depression. This review focuses on recent evidence that has added a new layer of complexity to the idea of targeting the eCB system for therapeutic benefits in neuropsychiatric disease and on the future research direction of neural circuit modulation.” 

https://www.nature.com/articles/s41401-018-0051-5

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Hippocampal mammalian target of rapamycin is implicated in stress-coping behavior induced by cannabidiol in the forced swim test.

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“Cannabidiol is a non-psychotomimetic compound with antidepressant-like effects.

However, the mechanisms and brain regions involved in cannabidiol effects are not yet completely understood. Brain-derived neurotrophic factor/tropomyosin-receptor kinase B/mammalian target of rapamycin (BDNF-TrkB-mTOR) signaling, especially in limbic structures, seems to play a central role in mediating the effects of antidepressant drugs.

RESULTS:

Systemic cannabidiol administration induced antidepressant-like effects and increased BDNF levels in the dorsal hippocampus. Rapamycin, but not K252a, injection into the dorsal hippocampus prevented the antidepressant-like effect induced by systemic cannabidiol treatment (10 mg/kg). Differently, hippocampal administration of cannabidiol (10 nmol/0.2 µL) reduced immobility time, an effect that was blocked by both rapamycin and K252a local microinjection.

CONCLUSION:

Altogether, our data suggest that the hippocampal BDNF-TrkB-mTOR pathway is vital for cannabidiol-induced antidepressant-like effect when the drug is locally administered. However, other brain regions may also be involved in cannabidiol-induced antidepressant effect upon systemic administration.”

https://www.ncbi.nlm.nih.gov/pubmed/29968502

http://journals.sagepub.com/doi/abs/10.1177/0269881118784877?journalCode=jopa

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Evidence for the use of “medical marijuana” in psychiatric and neurologic disorders.

College of Psychiatric and Neurologic Pharmacists

“Cannabis is listed as a Schedule I substance under the Controlled Substances Act of 1970, meaning the US federal government defines it as an illegal drug that has high potential for abuse and no established medical use; however, half of the states in the nation have enacted “medical marijuana” (MM) laws. Clinicians must be aware of the evidence for and against the use of MM in their patients who may consider using this substance.

RESULTS:

Publications were identified that included patients with dementia, multiple sclerosis, Parkinson disease, Huntington disease, schizophrenia, social anxiety disorder, depression, tobacco use disorder, and neuropathic pain.

DISCUSSION:

There is great variety concerning which medical conditions are approved for treatment with MM for either palliative or therapeutic benefit, depending on the state law. It is important to keep an evidence-based approach in mind, even with substances considered to be illegal under US federal law. Clinicians must weigh risks and benefits of the use of MM in their patients and should ensure that patients have tried other treatment modalities with higher levels of evidence for use when available and appropriate.”

https://www.ncbi.nlm.nih.gov/pubmed/29955495

““Medical marijuana” encompasses everything from whole-plant cannabis to synthetic cannabinoids available for commercial use approved by regulatory agencies. In determining whether MM is of clinical utility to our patients, it is important to keep in mind chemical constituents, dose, delivery, and indication. Selection of the patient appropriate for MM must be carefully considered because clinical guidelines and treatment options with stronger levels of evidence should be exhausted first in most cases. There seems to be strongest evidence for the use of MM in patients with MS and in patients with neuropathic pain; moderate evidence exists to support further research in social anxiety disorder, schizophrenia, PD, and tobacco use disorder; evidence is limited for use in patients with dementia, Huntington disease, depression, and anorexia.”

http://mhc.cpnp.org/doi/10.9740/mhc.2017.01.029?code=cpnp-site

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Antidepressant-like effect induced by Cannabidiol is dependent on brain serotonin levels.

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“Cannabidiol (CBD) is a compound of Cannabis sativa with relevant therapeutic potential in several neuropsychiatric disorders including depression. CBD treatment has shown significant antidepressant-like effects in different rodent preclinical models.

However, the mechanisms involved in CBD-induced antidepressant effects are still poorly understood. Therefore, this work aimed at investigating the participation of serotonin (5-HT) and/or noradrenaline (NA) in CBD-induced antidepressant-like effects in the forced swimming test (FST) by: 1) testing if CBD co-administration with serotonergic (fluoxetine, FLX) or noradrenergic (desipramine, DES) antidepressants would have synergistic effects; and 2) investigating if 5-HT or NA depletion would impair CBD-induced behavioral effects.

Results showed that CBD (10 mg/kg), FLX (10 mg/kg) and DES (5 mg/kg) induced antidepressant-like effects in mice submitted to FST. Ineffective doses of CBD (7 mg/kg), when co-administered with ineffective doses of FLX (5 mg/kg) or DES (2.5 mg/kg) resulted in significant antidepressant-like effects, thus implicating synergistic and/or additive mechanisms.

Pretreatment with PCPA (an inhibitor of serotonin synthesis: 150 mg/kg, i.p., once per day for 4 days), but not DSP-4 (a noradrenergic neurotoxin: 1 μg/μl, i.c.v., 24 h before the test), reduced monoamine levels in the brain. However, only PCPA treatment abolished CBD-induced behavioral effects in FST, indicating the participation of serotonergic mechanisms. None of the treatments induced locomotor effects.

Our results suggest that the antidepressant-like effect induced by CBD in the FST is dependent on serotonin levels in the central nervous system (CNS).”

https://www.ncbi.nlm.nih.gov/pubmed/29885468

https://www.sciencedirect.com/science/article/pii/S0278584618301167

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Sub-chronic treatment with cannabidiol but not with URB597 induced a mild antidepressant-like effect in diabetic rats.

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“Depression associated with diabetes has been described as a highly debilitating comorbidity. Due to its complex and multifactorial mechanisms, the treatment of depression associated with diabetes represents a clinical challenge.

Cannabidiol (CBD), the non-psychotomimetic compound derived from Cannabis sativa, has been pointed out as a promising compound for the treatment of several psychiatric disorders.

Here, we evaluated the potential antidepressant-like effect of acute or sub-chronic treatment with CBD in diabetic rats using the modified forced swimming test (mFST).

Also, to better understand the functionality of the endocannabinoid system in diabetic animals we also evaluated the effect of URB597, a fatty acid amide hydrolase inhibitor.

Acute treatment with either CBD or URB induced an antidepressant-like effect in NGL rats, but not in DBT rats. However, sub-chronic treatment with CBD (only at a dose of 30 mg/kg), but not with URB597, induced a mild antidepressant-like effect in DBT animals. Neither body weight nor blood glucose levels were altered by treatments.

Considering the importance of the endocannabinoid system to the mechanism of action of many antidepressant drugs, the mild antidepressant-like effect of the sub-chronic treatment with CBD, but not with URB597 does not invalidate the importance of deepening the studies involving the endocannabinoid system particularly in DBT animals.”

https://www.ncbi.nlm.nih.gov/pubmed/29885450

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Cannabidiol Induces Rapid and Sustained Antidepressant-Like Effects Through Increased BDNF Signaling and Synaptogenesis in the Prefrontal Cortex.

Molecular Neurobiology

“Currently available antidepressants have a substantial time lag to induce therapeutic response and a relatively low efficacy. The development of drugs that addresses these limitations is critical to improving public health.

Cannabidiol (CBD), a non-psychotomimetic component of Cannabis sativa, is a promising compound since it shows large-spectrum therapeutic potential in preclinical models and humans.

However, its antidepressant properties have not been completely investigated. Therefore, the aims of this study were to investigate in male rodents (i) whether CBD could induce rapid and sustained antidepressant-like effects after a single administration and (ii) whether such effects could be related to changes in synaptic proteins/function.

These results indicate that CBD induces fast and sustained antidepressant-like effect in distinct animal models relevant for depression. These effects may be related to rapid changes in synaptic plasticity in the mPFC through activation of the BDNF-TrkB signaling pathway.

The data support a promising therapeutic profile for CBD as a new fast-acting antidepressant drug.”

https://www.ncbi.nlm.nih.gov/pubmed/29869197

https://link.springer.com/article/10.1007%2Fs12035-018-1143-4

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Review of the neurological benefits of phytocannabinoids.

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“Numerous physical, psychological, and emotional benefits have been attributed to marijuana since its first reported use in 2,600 BC in a Chinese pharmacopoeia. The phytocannabinoids, cannabidiol (CBD), and delta-9-tetrahydrocannabinol (Δ9-THC) are the most studied extracts from cannabis sativa subspecies hemp and marijuana. CBD and Δ9-THC interact uniquely with the endocannabinoid system (ECS). Through direct and indirect actions, intrinsic endocannabinoids and plant-based phytocannabinoids modulate and influence a variety of physiological systems influenced by the ECS.

METHODS:

In 1980, Cunha et al. reported anticonvulsant benefits in 7/8 subjects with medically uncontrolled epilepsy using marijuana extracts in a phase I clinical trial. Since then neurological applications have been the major focus of renewed research using medical marijuana and phytocannabinoid extracts.

RESULTS:

Recent neurological uses include adjunctive treatment for malignant brain tumors, Parkinson’s disease, Alzheimer’s disease, multiple sclerosis, neuropathic pain, and the childhood seizure disorders Lennox-Gastaut and Dravet syndromes. In addition, psychiatric and mood disorders, such as schizophrenia, anxiety, depression, addiction, postconcussion syndrome, and posttraumatic stress disorders are being studied using phytocannabinoids.

CONCLUSIONS:

In this review we will provide animal and human research data on the current clinical neurological uses for CBD individually and in combination with Δ9-THC. We will emphasize the neuroprotective, antiinflammatory, and immunomodulatory benefits of phytocannabinoids and their applications in various clinical syndromes.”

https://www.ncbi.nlm.nih.gov/pubmed/29770251

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5938896/

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Adolescent chronic mild stress alters hippocampal CB1 receptor-mediated excitatory neurotransmission and plasticity

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“Endocannabinoids (eCBS) are involved in the stress response and alterations in eCB signaling may contribute to the etiology of mood disorders.

Exposure to chronic mild stress (CMS), a model of depression, produces downregulation of the CB1 receptor (CB1) in the hippocampus of male rats.

These results effectively demonstrate that CMS significantly alters hippocampal eCB-mediated neurotransmission and synaptic plasticity.”

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3827785/

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Deficiency in endocannabinoid signaling in the nucleus accumbens induced by chronic unpredictable stress.

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“The nucleus accumbens (NAc) is a critical component of the reward circuitry, and dysfunction of the NAc may account for anhedonia and other symptoms of depression.

The endocannabinoid (eCB) system regulates mood, emotion, motivation, appetite, body weight, and cognition.

Here, we investigated whether alterations in endocannabinoid (eCB) signaling in the NAc contribute to depression-like behaviors induced by chronic unpredictable stress (CUS) in mice.

These results suggest that downregulation of eCB signaling in the NAc occurs after CUS and contributes to the pathophysiology of depression.”

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Prolonged Cannabidiol Treatment Effects on Hippocampal Subfield Volumes in Current Cannabis Users.

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“Chronic cannabis use is associated with neuroanatomical alterations in the hippocampus. While adverse impacts of cannabis use are generally attributed to Δ9-tetrahydrocannabinol, emerging naturalistic evidence suggests cannabidiol (CBD) is neuroprotective and may ameliorate brain harms associated with cannabis use, including protection from hippocampal volume loss. This study examined whether prolonged administration of CBD to regular cannabis users within the community could reverse or reduce the characteristic hippocampal harms associated with chronic cannabis use.

Results: No change was observed in left or right hippocampus as a whole. However, left subicular complex (parasubiculum, presubiculum, and subiculum) volume significantly increased from baseline to post-treatment (p=0.017 uncorrected) by 1.58% (Cohen’s d=0.63; 2.83% in parasubiculum). Heavy cannabis users demonstrated marked growth in the left subicular complex, predominantly within the presubiculum, and right cornu ammonis (CA)1 compared to lighter users. Associations between greater right subicular complex and total hippocampal volume and higher plasma CBD concentration were evident, particularly in heavy users.

Conclusions: Our findings suggest a restorative effect of CBD on the subicular and CA1 subfields in current cannabis users, especially those with greater lifetime exposure to cannabis. While replication is required in a larger, placebo-controlled trial, these findings support a protective role of CBD against brain structural harms conferred by chronic cannabis use. Furthermore, these outcomes suggest that CBD may be a useful adjunct in treatments for cannabis dependence and may be therapeutic for a range of clinical disorders characterized by hippocampal pathology (e.g., schizophrenia, Alzheimer’s disease, and major depressive disorder).”

https://www.ncbi.nlm.nih.gov/pubmed/29682609

“In conclusion, our findings are the first to demonstrate an ameliorating effect of CBD treatment upon brain structural harms characteristic of regular cannabis use. Furthermore, these results speak to the potential for CBD treatment to restore hippocampal pathology in a range of clinical populations (e.g., schizophrenia, Alzheimer’s disease, and major depressive disorder).”

https://www.liebertpub.com/doi/10.1089/can.2017.0047

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