Tag Archives: endocannabinoid

Cannabinoid agonist WIN-55,212-2 partially restores neurogenesis in the aged rat brain

Posted on by
Reply

“A decline in neurogenesis in the hippocampus may underlie age-related memory impairment in rats and humans. We now show that WIN 55,212-2 administration for 3 weeks can partially restore neurogenesis in the hippocampus of aged rats. Cannabinoid receptor stimulation therapy may thus provide clinical benefit for humans with age-associated memory impairment.”

“This report shows for the first time the potential therapeutic efficacy of endocannabinoid receptor stimulation in stimulating neurogenesis from proliferation to engraftment during normal aging in vivo. The current results, coupled with our previous observations regarding the role of endocannabinoid receptors, underscores the potential clinical benefits of cannabinoid pharmacotherapies during normal and pathological brain aging.”

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3011092/

Enhancement of endocannabinoid neurotransmission through CB1 cannabinoid receptors counteracts the reinforcing and psychostimulant effects of cocaine.

Posted on by
Reply

Abstract

“Cannabinoids, in contrast to typical drugs of abuse, have been shown to exert complex effects on behavioural reinforcement and psychomotor function. We have shown that cannabinoid agonists lack reinforcing/rewarding properties in the intracranial self-stimulation (ICSS) paradigm and that the CB1 receptor (CB1R) agonist WIN55,212-2 attenuates the reward-facilitating actions of cocaine. We sought to determine the effects of the endocannabinoid neurotransmission enhancer AM-404 (1, 3, 10, 30 mg/kg) on the changes in ICSS threshold and locomotion elicited by cocaine and extend the study of the effects of WIN55,212-2 (0.3, 1, 3 mg/kg) on cocaine-induced hyperlocomotion. AM-404 did not exhibit reward-facilitating properties, and actually increased self-stimulation threshold at the highest dose. Cocaine significantly reduced self-stimulation threshold, without altering maximal rates of responding. AM-404 (10 mg/kg) attenuated this action of cocaine, an effect which was reversed by pretreatment with the selective CB1R antagonist SR141716A. WIN55,212-2 decreased locomotion at the two highest doses, an effect that was blocked by SR141716A; AM-404 had no effect on locomotion. Cocaine caused a significant, dose-dependent increase in locomotion, which was reduced by WIN55,212-2 and AM-404. SR141716A blocked the effects of WIN55,212-2 and AM-404 on cocaine-induced hyperlocomotion. SR141716A alone had no effect on ICSS threshold or locomotion. These results indicate that cannabinoids may interfere with brain reward systems responsible for the expression of acute reinforcing/rewarding properties of cocaine, and provide further evidence that the cannabinoid system could be explored as a potential drug discovery target for the treatment of psychostimulant addiction and pathological states associated with psychomotor overexcitability.”

http://www.ncbi.nlm.nih.gov/pubmed/18377702

The role of endocannabinoid transmission in cocaine addiction.

Posted on by
Reply

Abstract

“Research is beginning to outline a role for the endocannabinoid system in cocaine addiction. Human and animal studies indicate that exogenous cannabinoids modulate the acute rewarding effects of cocaine. These studies, however, cannot directly investigate the necessity of endocannabinoid transmission in cocaine addiction. Studies that do offer a direct assessment show that neither pharmacological antagonism nor deletion of the CB1 receptor alters the acute rewarding effects of cocaine. In contrast, CB1 receptors appear to be involved in the association of cocaine reward with environmental cues and reinstatement of cocaine self-administration. Together, these results point to CB1 receptor antagonists as potential anti-craving compounds in the treatment of cocaine addiction. Given the limitations of human population studies, animal research may be useful in discerning causal inferences between cannabis and cocaine use. While animal research suggests cannabis use may precipitate cocaine relapse, cross-sensitization between cannabinoids and cocaine has not been demonstrated and CB1 receptors do not mediate behavioral sensitization to cocaine. The effect of acute or chronic cocaine on endocannabinoid transmission in reward-related areas of the brain is relatively under-researched. Acute cocaine administration increases anandamide levels in the striatum, an effect that is mediated by dopamine D2-like receptors. Conversely, chronic cocaine exposure has no effect on anandamide, but decreases 2-arachidonylglycerol levels in the limbic forebrain. This review highlights research indicating that the endocannabinoid system may subserve certain aspects of cocaine addiction and suggests avenues for future investigation.”

http://www.ncbi.nlm.nih.gov/pubmed/15925401

An endocannabinoid hypothesis of drug reward and drug addiction.

Posted on by
Reply

Abstract

“Pharmacologic treatment of drug and alcohol dependency has largely been disappointing, and new therapeutic targets and hypotheses are needed. There is accumulating evidence indicating a central role for the previously unknown but ubiquitous endocannabinoid physiological control system (EPCS) in the regulation of the rewarding effects of abused substances. Thus an endocannabinoid hypothesis of drug reward is postulated. Endocannabinoids mediate retrograde signaling in neuronal tissues and are involved in the regulation of synaptic transmission to suppress neurotransmitter release by the presynaptic cannabinoid receptors (CB-Rs). This powerful modulatory action on synaptic transmission has significant functional implications and interactions with the effects of abused substances. Our data, along with those from other investigators, provide strong new evidence for a role for EPCS modulation in the effects of drugs of abuse, and specifically for involvement of cannabinoid receptors in the neural basis of addiction. Cannabinoids and endocannabinoids appear to be involved in adding to the rewarding effects of addictive substances, including, nicotine, opiates, alcohol, cocaine, and BDZs. The results suggest that the EPCS may be an important natural regulatory mechanism for drug reward and a target for the treatment of addictive disorders.”

http://www.ncbi.nlm.nih.gov/pubmed/18991888

An endocannabinoid mechanism in relapse to drug seeking: a review of animal studies and clinical perspectives.

Posted on by
Reply

Abstract

“Detoxification from drug abuse is strongly threatened by the occurrence of renewed episodes of drug intake. In human addicts, relapse to drug seeking may take place even after a considerably long period from the last drug consumption. Over the last decade, the endocannabinoid system has received remarkable attention due to its unique features, including its rewarding properties closely resembling those of the most commonly abused substances and its multiple therapeutic implications. Although limited at present, evidence is now emerging on a possible participation of the endogenous cannabinoid system in the regulation of relapsing phenomena. Both stimulation and blockade of the central cannabinoid CB-sub1 receptor have proved to play an important role in drug- as well as in cue-induced reinstatement of drug seeking behavior. Indeed, while CB-sub1 receptor stimulation may elicit relapse not only to cannabinoid seeking but also to cocaine, heroin, alcohol and methamphetamine, this effect is significantly attenuated, when not fully prevented, by pretreatment with the CB-sub1 receptor antagonist rimonabant. However, corroborating data on the involvement of the cannabinoid system in stress-induced reinstatement are still rather scarce. The present review attempts to collect data obtained from different laboratories using diverse experimental approaches, to provide a comprehensive picture of the recent evidence of a relationship between the cannabinoid system and the neurobiological mechanisms leading to relapse. For each class of abused drugs, the conspicuous progress made in delineating the role of the endocannabinoid system in relapse to drug seeking has been examined by placing particular emphasis on the findings obtained from behavioral studies. After summarizing findings and implications emerging from the reviewed studies, we conclude by briefly discussing what information is still missing and how missing information might be obtained.”

http://www.ncbi.nlm.nih.gov/pubmed/16839608

Obesity-dependent cannabinoid modulation of proliferation in adult neurogenic regions.

Posted on by
Reply

Abstract

“Endocannabinoid signalling participates in the control of neurogenesis, especially after brain insults. Obesity may explain alterations in physiology affecting neurogenesis, although it is unclear whether cannabinoid signalling may modulate neural proliferation in obese animals. Here we analyse the impact of obesity by using two approaches, a high-fat diet (HFD, 60% fat) and a standard/low-fat diet (STD, 10% fat), and the response to a subchronic treatment with the cannabinoid receptor type 1 (CB1) inverse agonist AM251 (3 mg/kg) on cell proliferation of two relevant neurogenic regions, namely the subventricular zone in the striatal wall of the lateral ventricle (SVZ) and the subgranular zone of the dentate gyrus (SGZ), and also in the hypothalamus given its role in energy metabolism. We found evidence of an interaction between diet-induced obesity and CB1 signalling in the regulation of cell proliferation. AM251 reduced caloric intake and body weight in obese rats, as well as corrected plasma levels of cholesterol and triglycerides. AM251 is shown, for the first time, to modulate cell proliferation in HFD-obese rats only. We observed an increase in the number of 5-bromo-2-deoxyuridine-labelled (BrdU+) cells in the SGZ, but a decrease in the number of BrdU+ cells in the SVZ and the hypothalamus of AM251-treated HFD rats. These BrdU+ cells expressed the neuron-specific βIII-tubulin. These results suggest that obesity may impact cell proliferation in the brain selectively, and provide support for a role of CB1 signalling regulation of neurogenesis in response to obesity.”

http://www.ncbi.nlm.nih.gov/pubmed/21395869

Obesity, the Endocannabinoid System, and Bias Arising from Pharmaceutical Sponsorship

Posted on by
Reply

“Previous research has shown that academic physicians conflicted by funding from the pharmaceutical industry have corrupted evidence based medicine and helped enlarge the market for drugs. Physicians made pharmaceutical-friendly statements, engaged in disease mongering, and signed biased review articles ghost-authored by corporate employees.

 This paper tested the hypothesis that bias affects review articles regarding rimonabant, an anti-obesity drug that blocks the central cannabinoid receptor.

CONCLUSIONS:

The findings are characteristic of bias that arises from financial conflicts of interest, and suggestive of ghostwriting by a common author. Resolutions for this scenario are proposed.

In summary, financial conflicts permeate the system and are by no means limited to corporations referenced in this article, such as Merck, Parke-Davis, Pfizer, Sanofi-Aventis, and Wyeth-Ayerst. On balance, pharmaceutical corporations do good work and aid in humanitarian efforts. For example Sanofi-Aventis provides artemisinin at cost to malaria-endemic countries. Nevertheless, ghost authorship and the corrupting effects of covert financial support must cease. Only three of eight rimonabant review articles disclosed corporate sponsorship; two authors specifically denied conflicts. Lack of disclosure prevents readers from judging the credibility of an author. Medical journals should require stronger author disclosure procedures, and universities should discipline academics who sign ghostwritten articles. This behavior should be regarded as unethical misconduct. More broadly, researchers with conflicts of interest should not be allowed to sit on guideline committees and regulatory boards. Corporate funding of CME programs and review articles should be abolished.

While this paper was under review, Merck halted taranabant RCTs, and Sanofi-Aventis removed rimonabant from the European market. The FDA rejected rimonabant after data submitted by Sanofi-Aventis revealed adverse effects in RIO trials that went unreported in RIO publications [86], including one death in a rimonabant-treated subject (ruled a suicide by the FDA, [86]) that did not appear in the pertinent publication [7]. Although the risk-benefit ratio of cannabinoid receptor blockade may preclude its use for chronic conditions such as obesity and drug or alcohol dependence, cannabinoid receptor blockade could serve in the treatment of acute endocannabinoid dysregulation, such as hepatic cirrhosis, hemorrhagic or endotoxic shock, cardiac reperfusion injury, and doxorubicin-induced cardiotoxicity.”

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2659447/

 

Cannabinoid receptor antagonists: pharmacological opportunities, clinical experience, and translational prognosis.

Posted on by
2

Abstract

“The endogenous cannabinoid (CB) (endocannabinoid) signaling system is involved in a variety of (patho)physiological processes, primarily by virtue of natural, arachidonic acid-derived lipids (endocannabinoids) that activate G protein-coupled CB1 and CB2 receptors. A hyperactive endocannabinoid system appears to contribute to the etiology of several disease states that constitute significant global threats to human health. Consequently, mounting interest surrounds the design and profiling of receptor-targeted CB antagonists as pharmacotherapeutics that attenuate endocannabinoid transmission for salutary gain. Experimental and clinical evidence supports the therapeutic potential of CB1 receptor antagonists to treat overweight/obesity, obesity-related cardiometabolic disorders, and substance abuse. Laboratory data suggest that CB2 receptor antagonists might be effective immunomodulatory and, perhaps, anti-inflammatory drugs. One CB1 receptor antagonist/inverse agonist, rimonabant, has emerged as the first-in-class drug approved outside the United States for weight control. Select follow-on agents (taranabant, otenabant, surinabant, rosonabant, SLV-319, AVE1625, V24343) have also been studied in the clinic. However, rimonabant’s market withdrawal in the European Union and suspension of rimonabant’s, taranabant’s, and otenabant’s ongoing development programs have highlighted some adverse clinical side effects (especially nausea and psychiatric disturbances) of CB1 receptor antagonists/inverse agonists. Novel CB1 receptor ligands that are peripherally directed and/or exhibit neutral antagonism (the latter not affecting constitutive CB1 receptor signaling) may optimize the benefits of CB1 receptor antagonists while minimizing any risk. Indeed, CB1 receptor-neutral antagonists appear from preclinical data to offer efficacy comparable to or better than that of prototype CB1 receptor antagonists/inverse agonists, with less propensity to induce nausea. Continued pharmacological profiling, as the prelude to first-in-man testing of CB1 receptor antagonists with unique modes of targeting/pharmacological action, represents an exciting translational frontier in the critical path to CB receptor blockers as medicines.”

http://www.ncbi.nlm.nih.gov/pubmed/19249987