Tag Archives: CB1

Cannabis reinforcement and dependence: role of the cannabinoid CB1 receptor.

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Abstract

“Awareness of cannabis dependence as a clinically relevant issue has grown in recent years. Clinical and laboratory studies demonstrate that chronic marijuana smokers can experience withdrawal symptoms upon cessation of marijuana smoking and have difficulty abstaining from marijuana use. This paper will review data implicating the cannabinoid CB1 receptor in regulating the behavioral effects of Δ9-tetrahydrocannobinol (THC), the primary psycho-active component of cannabis, across a range of species. The behavioral effects that will be discussed include those that directly contribute to the maintenance of chronic marijuana smoking, such as reward, subjective effects, and the positive and negative reinforcing effects of marijuana, THC and synthetic cannabinoids. The role of the CB1 receptor in the development of marijuana dependence and expression of withdrawal will also be discussed. Lastly, treatment options that may alleviate withdrawal symptoms and promote marijuana abstinence will be considered.”

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2731704/

Dronabinol for the Treatment of Cannabis Dependence: A Randomized, Double-Blind, Placebo-Controlled Trial

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   “The purpose of this study was to evaluate the safety and efficacy of dronabinol, a synthetic form of delta-9-tetrahydrocannabinol, a naturally occurring pharmacologically active component of marijuana, in treating cannabis dependence… This is the first trial using an agonist substitution strategy for treatment of cannabis dependence. Dronabinol showed promise, it was well-tolerated, and improved treatment retention and withdrawal symptoms. Future trials might test higher doses, combinations of dronabinol with other medications with complementary mechanisms, or with more potent behavioral interventions.

The agonist substitution strategy has been effective for other substance use disorders, mainly nicotine (nicotine patch, other nicotine replacement products, varenicline) and opioid dependence (methadone, buprenorphine). Therefore, dronabinol, an orally bioavailable synthetic form of delta-9-tetrahydrocannabinol (THC), the main psychoactive component of marijuana acting at the cannabinoid 1 (CB1) receptor, seems a logical candidate medication for cannabis dependence. An ideal agonist medication has low abuse potential, reduces withdrawal symptoms and craving, and decreases the reinforcing effects of the target drug, thereby facilitating abstinence. Dronabinol has been shown to reduce cannabis withdrawal symptoms in laboratory settings among non-treatment seeking cannabis users. Although dronabinol produced modest positive subjective effects among cannabis users in the laboratory, there is little evidence of abuse or diversion of dronabinol in community settings. We conducted a randomized, placebo-controlled trial to evaluate the safety and efficacy of dronabinol for patients seeking treatment for cannabis dependence. This is, to our knowledge, the largest clinical trial to date to evaluate a pharmacologic intervention for cannabis dependence, and the first to attempt agonist substitution.

.In conclusion, agonist substitution pharmacotherapy with dronabinol, a synthetic form of THC, showed promise for treatment of cannabis dependence, reducing withdrawal symptoms and improving retention in treatment, although it failed to improve abstinence. The trial showed that among adult cannabis-dependent patients, dronabinol was well accepted, with good adherence and few adverse events. Future studies should consider testing higher doses of dronabinol, with longer trial lengths, combining dronabinol with other medications acting through complementary mechanisms or more potent behavioral interventions. Moreover, the field should particularly seek to develop high affinity CB1 partial agonists.”

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3154755/

Substitution profile of the cannabinoid agonist nabilone in human subjects discriminating δ9-tetrahydrocannabinol.

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Abstract

“OBJECTIVES:

The central effects of Δ-tetrahydrocannabinol (Δ-THC), the primary active constituent of cannabis, are attributed to cannabinoid CB1 receptor activity, although clinical evidence is limited. Drug discrimination has proven useful for examining the neuropharmacology of drugs, as data are concordant with the actions of a drug at the receptor level. The aim of this study was to determine the profile of behavioral and physiological effects of the cannabinoid agonist nabilone in humans trained to discriminate Δ-THC.

METHODS:

Six cannabis users learned to identify when they received oral Δ-THC (25 mg) or placebo and then received a range of doses of the cannabinoid agonists nabilone (1, 2, 3, and 5 mg) and Δ-THC (5, 10, 15, and 25 mg). The dopamine reuptake inhibitor methylphenidate (5, 10, 20, and 30 mg) was included as a negative control. Subjects completed the Multiple-Choice Procedure, and self-report, task performance, and physiological measures were collected.

RESULTS:

Nabilone shared discriminative-stimulus effects with the training dose of Δ-THC, produced subject-rated drug effects that were comparable to those of Δ-THC, and increased heart rate. Methylphenidate did not engender Δ-THC-like discriminative-stimulus effects.

CONCLUSIONS:

These data demonstrate that the interoceptive effects of nabilone are similar to Δ-THC in cannabis users. The overlap in their behavioral effects is likely due to their shared mechanism as CB1 receptor agonists. Given the relative success of agonist replacement therapy to manage opioid, tobacco, and stimulant dependence, these results also support the evaluation of nabilone as a potential medication for cannabis-use disorders.”

http://www.ncbi.nlm.nih.gov/pubmed/20838217

Central and peripheral mechanisms contribute to the antiemetic actions of delta-9-tetrahydrocannabinol against 5-hydroxytryptophan-induced emesis.

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Abstract

“Delta-9-tetrahydrocannabinol (delta-9-THC) prevents cisplatin-induced emesis via cannabinoid CB(1) receptors. Whether central and/or peripheral cannabinoid CB(1) receptors account for the antiemetic action(s) of delta-9-THC remains to be investigated. The 5-hydroxytryptamine (5-HT=serotonin) precursor, 5-hydroxytryptophan (5-HTP), is an indirect 5-HT agonist and simultaneously produces the head-twitch response (a centrally mediated serotonin 5-HT(2A) receptor-induced behavior) and emesis (a serotonin 5-HT(3) receptor-induced response, mediated by both peripheral and central mechanisms) in the least shrew (Cryptotis parva). The peripheral amino acid decarboxylase inhibitor, carbidopa, prevents the conversion of 5-HTP to 5-HT in the periphery and elevates 5-HTP levels in the central nervous system (CNS). When administered i.p. alone, a 50 mg/kg dose of 5-HTP failed to induce either behaviour while its 100 mg/kg dose produced robust frequencies of both head-twitch response and emesis. Pretreatment with carbidopa (0, 10, 20 and 40 mg/kg) potentiated the ability of both doses of 5-HTP to produce the head-twitch response in a dose-dependent but bell-shaped manner, with maximal potentiation occurring at 20 mg/kg carbidopa. Carbidopa dose-dependently reduced the frequency of 5-HTP (100 mg/kg)-induced emesis, whereas the 10 mg/kg dose potentiated, and the 20 and 40 mg/kg doses suppressed the frequency of vomits produced by the 50 mg/kg dose of 5-HTP. The peripheral and/or central antiemetic action(s) of delta-9-THC (0, 1, 2.5, 5, 10 and 20 mg/kg) against 5-HTP (100 mg/kg)-induced head-twitch response and emesis were investigated in different groups of carbidopa (0, 10 and 20 mg/kg) pretreated shrews. Irrespective of carbidopa treatment, delta-9-THC attenuated the frequency of 5-HTP-induced head-twitch response in a dose-dependent manner with similar ID(50) values. Although delta-9-THC also reduced the frequency of 5-HTP-induced emesis with similar ID(50s), at the 5 mg/kg delta-9-THC dose however, 5-HTP induced significantly less vomits in the 10 and 20 mg/kg carbidopa-treated groups relative to its 0 mg/kg control group. Moreover, increasing doses of carbidopa significantly shifted the inhibitory dose-response effect of delta-9-THC in protecting shrews from 5-HTP-induced emesis to the left. Relatively, a large dose of delta-9-THC (20 mg/kg) was required to significantly reduce the number of vomits produced by direct acting serotonergic 5-HT(3) receptor agonists, serotonin and 2-methylserotonin. Low doses of delta-9-THC (0.1-1 mg/kg) nearly completely prevented 2-methylserotonin-induced, centrally mediated, head-twitch and ear-scratch responses. The results indicate that delta-9-THC probably acts pre- and postsynaptically to attenuate emesis produced by indirect and direct acting 5-HT(3) receptor agonists via both central and peripheral mechanisms. In addition, delta-9-THC prevents 5-HTP-induced head-twitch and emesis via cannabinoid CB(1) receptors since the CB(1) receptor antagonist, SR 141716A [N-piperidino-5-(4-chlorophenyl)-1-(2,4-dichlorophenyl)-4-methylpyrazole-3-carboxamide], countered the inhibitory actions of an effective dose of delta-9-THC against both behaviours.”

http://www.ncbi.nlm.nih.gov/pubmed/15044052

http://www.thctotalhealthcare.com/category/nauseavomiting/

Delta-9-tetrahydrocannabinol differentially suppresses cisplatin-induced emesis and indices of motor function via cannabinoid CB(1) receptors in the least shrew.

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“The present study investigates the cannabinoid receptor mechanisms by which Delta(9)-THC produces its antiemetic effects against cisplatin -induced emesis as well as its cannabimimetic activity profile (motor reduction) in the least shrew.

Intraperitoneal administration of Delta(9)-THC (1, 2.5, 5 and 10 mg/kg) dose-dependently reduced both the percentage of animals vomiting (ID(50)=1.8+/-1.6 mg/kg) and the frequency of vomits (ID(50)=0.36+/-1.18 mg/kg) in a potent manner.

The lowest significantly effective antiemetic dose of Delta(9)-THC for the latter emesis parameters was 2.5 mg/kg. Although Delta(9)-THC reduced the frequency of vomits up to 98%, it failed to completely protect all tested shrews from vomiting (80% protection). The cannabinoid CB(1) antagonist (SR 141716A) and not the CB(2) antagonist (SR 144528), reversed the antiemetic effects of Delta(9)-THC in a dose-dependent fashion. Delta(9)-THC (1, 5, 10 and 20 mg/kg, ip) suppressed locomotor parameters (spontaneous locomotor activity, duration of movement and rearing frequency) in a biphasic manner and only the 20-mg/kg dose simultaneously suppressed the triad of locomotor parameters to a significant degree. Subcutaneous (1-10 mg/kg) and intraperitoneal (0.05-40 mg/kg) injection of some doses of SR 141716A caused significant reductions in one or more components of the triad of locomotor parameters but these reductions were not dose dependent. Subcutaneous injection of SR 141716A (0.2, 1, 5 and 10 mg/kg) reversed the motor suppressant effects of a 20-mg/kg dose of Delta(9)-THC (ip) in a dose-dependent manner. Relative to its motor suppressant effects,

Delta(9)-THC is a more potent antiemetic agent. Both effects are probably mediated via CB(1) receptors in distinct loci.”

http://www.ncbi.nlm.nih.gov/pubmed/11420092

http://www.thctotalhealthcare.com/category/nauseavomiting/

Antiemetic and motor-depressive actions of CP55,940: cannabinoid CB1 receptor characterization, distribution, and G-protein activation.

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Abstract

“Dibenzopyran (Delta(9)-tetrahydrocannabinol) and aminoalkylindole [R(+)-[2,3-dihydro-5-methyl-3-[(morpholinyl)methyl]pyrolol[1,2,3-de]-1,4-benzoxazin-yl]-(1-naphthalenyl) methanone mesylate; (WIN55,212-2)] cannabinoids suppress vomiting produced by cisplatin via cannabinoid CB(1) receptors. This study investigates the antiemetic potential of the “nonclassical” cannabinoid CP55,940 [1alpha,2beta-(R)-5alpha]-(-)-5-(1,1-dimethyl)-2-[5-hydroxy-2-(3-hydroxypropyl) cyclohexyl-phenol] against cisplatin-induced vomiting and assesses the presence and functionality of cannabinoid CB(1) receptors in the least shrew (Cryptotis parva) brain. CP55,940 (0.025-0.3 mg/kg) reduced both the frequency of cisplatin-induced emesis (ID(50)=0.025 mg/kg) and the percentage of shrews vomiting (ID(50)=0.09 mg/kg). CP55,940 also suppressed shrew motor behaviors (ID(50)=0.06- 0.21 mg/kg) at such doses. The antiemetic and motor-suppressant actions of CP55,940 were countered by SR141716A [N-piperidino-5-(4-chlorophenyl)-1-(2,4-dichlorophenyl)-4-methylpyrazole-3-carboxamide], indicating both effects are cannabinoid CB(1) receptor-mediated. Autoradiographic studies with [3H]-SR141716A and [35S]-GTPgammaS binding revealed that the distribution of the cannabinoid CB(1) receptor and its activation pattern are similar to rodent brain and significant levels are present in brain loci (e.g., nucleus tractus solitarius (NTS)) that control emesis. The affinity rank order of structurally diverse cannabinoid ligands for cannabinoid CB(1) receptor in shrew brain is similar to rodent brain: HU-210=CP55,940=SR141716A>/=WIN55,212-2>/=delta-9-tetrahydrocannabinol>methanandamide=HU-211=cannabidiol=2-arachidonoylglycerol. This affinity order is also similar and is highly correlated to the cannabinoid EC(50) potency rank order for GTPgammaS stimulation except WIN55,212-2 and delta-9-tetrahydrocannabinol potency order were reversed. The affinity and the potency rank order of tested cannabinoids were significantly correlated with their antiemetic ID(50) potency order against cisplatin-induced vomiting (CP55,940>WIN55,212-2=delta-9-tetrahydrocannabinol) as well as emesis produced by 2-arachidonoylglycerol or SR141716A (CP55,940>WIN55,212-2>delta-9-tetrahydrocannabinol).”

http://www.ncbi.nlm.nih.gov/pubmed/12505537

Regulation of nausea and vomiting by cannabinoids.

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“Anti-emetic effects of cannabinoids in human clinical trials”

  “Considerable evidence demonstrates that manipulation of the endocannabinoid system regulates nausea and vomiting in humans and other animals. The anti-emetic effect of cannabinoids has been shown across a wide variety of animals that are capable of vomiting in response to a toxic challenge. CB1 agonism suppresses vomiting, which is reversed by CB1 antagonism, and CB1 inverse agonism promotes vomiting. Recently, evidence from animal experiments suggests that cannabinoids may be especially useful in treating the more difficult to control symptoms of nausea and anticipatory nausea in chemotherapy patients, which are less well controlled by the currently available conventional pharmaceutical agents. Although rats and mice are incapable of vomiting, they display a distinctive conditioned gaping response when re-exposed to cues (flavours or contexts) paired with a nauseating treatment. Cannabinoid agonists (Δ9-THC, HU-210) and the fatty acid amide hydrolase (FAAH) inhibitor, URB-597, suppress conditioned gaping reactions (nausea) in rats as they suppress vomiting in emetic species. Inverse agonists, but not neutral antagonists, of the CB1 receptor promote nausea, and at subthreshold doses potentiate nausea produced by other toxins (LiCl). The primary non-psychoactive compound in cannabis, cannabidiol (CBD), also suppresses nausea and vomiting within a limited dose range. The anti-nausea/anti-emetic effects of CBD may be mediated by indirect activation of somatodendritic 5-HT1A receptors in the dorsal raphe nucleus; activation of these autoreceptors reduces the release of 5-HT in terminal forebrain regions. Preclinical research indicates that cannabinioids, including CBD, may be effective clinically for treating both nausea and vomiting produced by chemotherapy or other therapeutic treatments.”

“The cannabis plant has been used for several centuries for a number of therapeutic applications, including the attenuation of nausea and vomiting. Ineffective treatment of chemotherapy-induced nausea and vomiting prompted oncologists to investigate the anti-emetic properties of cannabinoids in the late 1970s and early 1980s, before the discovery of the 5-HT3 antagonists. The first cannabinoid agonist, nabilone (Cesamet), which is a synthetic analogue of Δ9-THC was specifically licensed for the suppression of nausea and vomiting produced by chemotherapy. Furthermore, synthetic Δ9-THC, dronabinol, entered the clinic as Marinol in 1985 as an anti-emetic and in 1992 as an appetite stimulant. In these early studies, several clinical trials compared the effectiveness of Δ9-THC with placebo or other anti-emetic drugs. Comparisons of oral Δ9-THC with existing anti-emetic agents generally indicated that Δ9-THC was at least as effective as the dopamine antagonists, such as prochlorperazine.”

“There is some evidence that cannabis-based medicines may be effective in treating the more difficult to control symptoms of nausea and delayed nausea and vomiting in children. Abrahamov et al. (1995) evaluated the anti-emetic effectiveness of Δ8-THC, a close but less psychoactive relative of Δ9-THC, in children receiving chemotherapy treatment. Two hours before the start of each cancer treatment and every six hours thereafter for 24 h, the children were given Δ8-THC as oil drops on the tongue or in a bite of food. After a total of 480 treatments, the only side effects reported were slight irritability in two of the youngest children (3.5 and 4 years old); both acute and delayed nausea and vomiting were controlled.”

“Chemotherapy-induced vomiting is well controlled in most patients by conventionally available drugs, nausea (acute, delayed and anticipatory) continues to be a challenge. Nausea is often reported as more distressing than vomiting, because it is a continuous sensation. Indeed, this distressing symptom of chemotherapy treatment (even when vomiting is pharmacologically controlled) can become so severe that as many as 20% of patients discontinue the treatment. Both preclinical and human clinical research suggests that cannabinoid compounds may have promise in treating nausea in chemotherapy patients.”

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3165951/

Cannabis and endocannabinoid modulators: Therapeutic promises and challenges

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Abstract

  “The discovery that botanical cannabinoids such as delta-9 tetrahydrocannabinol exert some of their effect through binding specific cannabinoid receptor sites has led to the discovery of an endocannabinoid signaling system, which in turn has spurred research into the mechanisms of action and addiction potential of cannabis on the one hand, while opening the possibility of developing novel therapeutic agents on the other. This paper reviews current understanding of CB1, CB2, and other possible cannabinoid receptors, their arachidonic acid derived ligands (e.g. anandamide; 2 arachidonoyl glycerol), and their possible physiological roles. CB1 is heavily represented in the central nervous system, but is found in other tissues as well; CB2 tends to be localized to immune cells. Activation of the endocannabinoid system can result in enhanced or dampened activity in various neural circuits depending on their own state of activation. This suggests that one function of the endocannabinoid system may be to maintain steady state. The therapeutic action of botanical cannabis or of synthetic molecules that are agonists, antagonists, or which may otherwise modify endocannabinoid metabolism and activity indicates they may have promise as neuroprotectants, and may be of value in the treatment of certain types of pain, epilepsy, spasticity, eating disorders, inflammation, and possibly blood pressure control.”

Summary

“The discovery of an endocannabinoid signaling system has opened new possibilities for research into understanding the mechanisms of marijuana actions, the role of the endocannabinoid system in homeostasis, and the development of treatment approaches based either on the phytocannabinoids or novel molecules. CB1 agonists may have roles in the treatment of neuropathic pain, spasticity, nausea and emesis, cachexia, and potentially neuroprotection after stroke or head injury. Agonists and antagonists of peripheral CB receptors may be useful in the treatment of inflammatory and autoimmune disorders, as well as hypertension and other cardiovascular diseases. CB1 antagonists may find utility in management of obesity and drug craving. Other novel agents that may not be active at CB receptor sites, but might otherwise modify cannabinoid transport or metabolism, may also have a role in therapeutic modification of the endocannabinoid system. While the short and long term toxicities of the newer compounds are not known, one must expect that at least some of the acute effects (psychotropic effects; hypotension) may be shared by CB agonists. While there are few, long-term serious toxicities attributable to marijuana, extrapolation to newer and more potent agonists, antagonists, and cannabinoid system modulators cannot be assumed. CB1 agonists have the potential in animal models to produce drug preference and drug seeking behaviors as well as tolerance and abstinence phenomena similar to, though not generally as severe as those of other drugs of addiction. There is increasing evidence from human observations that withdrawal from the phytocannabinoids can produce an abstinence syndrome characterized primarily by irritability, sleep disturbance, mood disturbance, and appetite disturbance in chronic heavy users, therefore, such possible effects will need to be considered in the evaluation of newer shorter acting and more potent agonists.”

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2544377/

Cannabidiol Displays Antiepileptiform and Antiseizure Properties In Vitro and In Vivo

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“CBD is the major nonpsychoactive component of Cannabis sativa whose structure was first described by Mechoulam and Shvo (1963); CBD has recently attracted renewed interest for its therapeutic potential in a number of disease states. CBD has been proposed to possess anticonvulsive, neuroprotective, and anti-inflammatory properties in humans.”

 “Plant-derived cannabinoids (phytocannabinoids) are compounds with emerging therapeutic potential. Early studies suggested that cannabidiol (CBD) has anticonvulsant properties in animal models and reduced seizure frequency in limited human trials. Here, we examine the antiepileptiform and antiseizure potential of CBD using in vitro electrophysiology and an in vivo animal seizure model…. These findings suggest that CBD acts, potentially in a CB1 receptor-independent manner, to inhibit epileptiform activity in vitro and seizure severity in vivo. Thus, we demonstrate the potential of CBD as a novel antiepileptic drug in the unmet clinical need associated with generalized seizures.”

“In conclusion, our data in separate in vitro models of epileptiform activity and, in particular, the beneficial reductions in seizure severity caused by CBD in an in vivo animal model of generalized seizures suggests that earlier, small-scale clinical trials for CBD in untreated epilepsy warrant urgent renewed investigation.”

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2819831/

Δ⁹-Tetrahydrocannabivarin suppresses in vitro epileptiform and in vivo seizure activity in adult rats.

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“PURPOSE:

We assessed the anticonvulsant potential of the phytocannabinoid Δ⁹-tetrahydrocannabivarin (Δ⁹-THCV) by investigating its effects in an in vitro piriform cortex (PC) brain slice model of epileptiform activity, on cannabinoid CB1 receptor radioligand-binding assays and in a generalized seizure model in rats.”

“DISCUSSION:

These data demonstrate that Δ⁹-THCV exerts antiepileptiform and anticonvulsant properties, actions that are consistent with a CB1 receptor-mediated mechanism and suggest possible therapeutic application in the treatment of pathophysiologic hyperexcitability states.”

http://www.ncbi.nlm.nih.gov/pubmed/20196794