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PubMed2003

Evidence for cannabinoid receptor-dependent and -independent mechanisms of action in leukocytes.

Cannabinoids exhibit immunosuppressive actions that include inhibition of interleukin-2 production in response to a variety of T cell activation stimuli. Traditionally, the effects of these compounds have been attributed to cannabinoid receptors CB1 and CB2, both of which are expressed in mouse splenocytes. Therefore, N-(piperidin-1-yl)-5-(4-chlorophenyl)-1-(2,4-dichlorphenyl)-4-methyl-H-pyrazole-3 carboxyamidehydrochloride (SR141716A), a CB1 antagonist, and N-[(1S)-endo-1,3,3,-trimethyl-bicyclo[2,2,1]heptan-2-yl]-5-(4-chloro-3-methylphenyl)-1-(4-methylbenzyl)-pyrazole-3-carboxamide (SR144528), a CB2 antagonist, were used to investigate the role of cannabinoid receptors in the cannabinoid-induced inhibition of phorbol ester plus calcium ionophore (PMA/Io)-stimulated interleukin-2 production by mouse splenocytes. PMA/Io-stimulated interleukin-2 production was inhibited by cannabinol, cannabidiol, and both WIN 55212-2 stereoisomers with a rank order potency of R-(+)-[2,3-dihydro-5-methyl-3-[(morpholinyl)methyl]pyrrolo[1,2,3-de]-1,4-benzoxazinyl]-(1-napthanlenyl) methanone mesylate (WIN 55212-2) approximately cannabidiol > S-(-)-[2,3-dihydro-5-methyl-3-[(morpholinyl)methyl]pyrrolo[1,2,3-de]-1,4-benzoxazinyl]-(1-napthanlenyl) methanone mesylate (WIN 55212-3) approximately cannabinol. Cannabinoid-induced inhibition of PMA/Io-stimulated interleukin-2 was not attenuated by the presence of both SR144528 and SR141716A. Using pertussis toxin to address the role of G protein-coupled receptors in this response, it was determined that pertussis toxin treatment did not attenuate cannabinol-induced inhibition of PMA/Io-stimulated interleukin-2. With the demonstration that cannabinoid-induced inhibition of PMA/Io-stimulated interleukin-2 was not mediated via CB1 or CB2, alternative targets of cannabinoids in T cells were examined. Specifically, it was demonstrated that cannabinoids elevated intracellular calcium concentration in resting splenocytes and that the cannabinol-induced elevation in intracellular calcium concentration was attenuated by treatment with both SR144528 and SR141716A. Interestingly, pretreatment of splenocytes with agents that elevate intracellular calcium concentration inhibited PMA/Io-stimulated interleukin-2 production, suggesting that an elevation in intracellular calcium concentration might be involved in the mechanism of interleukin-2 inhibition. These studies suggest that immune modulation produced by cannabinoids involves multiple mechanisms, which might be both cannabinoid receptor-dependent and -independent.

Animals↗

PubMed2001

Cannabinoids and the gastrointestinal tract.

The enteric nervous system of several species, including the mouse, rat, guinea pig and humans, contains cannabinoid CB1 receptors that depress gastrointestinal motility, mainly by inhibiting ongoing contractile transmitter release. Signs of this depressant effect are, in the whole organism, delayed gastric emptying and inhibition of the transit of non-absorbable markers through the small intestine and, in isolated strips of ileal tissue, inhibition of evoked acetylcholine release, peristalsis, and cholinergic and non-adrenergic non-cholinergic (NANC) contractions of longitudinal or circular smooth muscle. These are contractions evoked electrically or by agents that are thought to stimulate contractile transmitter release either in tissue taken from morphine pretreated animals (naloxone) or in unpretreated tissue (gamma-aminobutyric acid and 5-hydroxytryptamine). The inhibitory effects of cannabinoid receptor agonists on gastric emptying and intestinal transit are mediated to some extent by CB1 receptors in the brain as well as by enteric CB1 receptors. Gastric acid secretion is also inhibited in response to CB1 receptor activation, although the detailed underlying mechanism has yet to be elucidated. Cannabinoid receptor agonists delay gastric emptying in humans as well as in rodents and probably also inhibit human gastric acid secretion. Cannabinoid pretreatment induces tolerance to the inhibitory effects of cannabinoid receptor agonists on gastrointestinal motility. Findings that the CB1 selective antagonist/inverse agonist SR141716A produces in vivo and in vitro signs of increased motility of rodent small intestine probably reflect the presence in the enteric nervous system of a population of CB1 receptors that are precoupled to their effector mechanisms. SR141716A has been reported not to behave in this manner in the myenteric plexus-longitudinal muscle preparation (MPLM) of human ileum unless this has first been rendered cannabinoid tolerant. Nor has it been found to induce "withdrawal" contractions in cannabinoid tolerant guinea pig ileal MPLM. Further research is required to investigate the role both of endogenous cannabinoid receptor agonists and of non-CB1 cannabinoid receptors in the gastrointestinal tract. The extent to which the effects on gastrointestinal function of cannabinoid receptor agonists or antagonists/inverse agonists can be exploited therapeutically has yet to be investigated as has the extent to which these drugs can provoke unwanted effects in the gastrointestinal tract when used for other therapeutic purposes.

Acetylcholine↗

PubMed1999

Behavioral effects of cannabinoid agents in animals.

Two subtypes of cannabinoid receptors have been identified to date, the CB1 receptor, essentially located in the CNS, but also in peripheral tissues, and the CB2 receptor, found only at the periphery. The identification of delta9-tetrahydrocannabinol (delta9-THC) as the major active component of marijuana (Cannabis sativa), the recent emergence of potent synthetic ligands and the identification of anandamide and sn-2 arachidonylglycerol as putative endogenous ligands for cannabinoid receptors in the brain, have contributed to advancing cannabinoid pharmacology and approaching the neurobiological mechanisms involved in physiological and behavioral effects of cannabinoids. Most of the agonists exhibit nonselective affinity for CB1/CB2 receptors, and delta9-THC and anandamide probably act as partial agonists. Some recently synthesized molecules are highly selective for CB2 receptors, whereas selective agonists for the CB1 receptors are not yet available. A small number of antagonists exist that display a high selectivity for either CB1 or CB2 receptors. Cannabinomimetics produce complex pharmacological and behavioral effects that probably involve numerous neuronal substrates. Interactions with dopamine, acetylcholine, opiate, and GABAergic systems have been demonstrated in several brain structures. In animals, cannabinoid agonists such as delta9-THC, WIN 55,212-2, and CP 55,940 produce a characteristic combination of four symptoms, hypothermia, analgesia, hypoactivity, and catalepsy. They are reversed by the selective CB1 receptor antagonist, SR 141716, providing good evidence for the involvement of CB1-related mechanisms. Anandamide exhibits several differences, compared with other agonists. In particular, hypothermia, analgesia, and catalepsy induced by this endogenous ligand are not reversed by SR 141716. Cannabinoid-related processes seem also involved in cognition, memory, anxiety, control of appetite, emesis, inflammatory, and immune responses. Agonists may induce biphasic effects, for example, hyperactivity at low doses and severe motor deficits at larger doses. Intriguingly, although cannabis is widely used as recreational drug in humans, only a few studies revealed an appetitive potential of cannabimimetics in animals, and evidence for aversive effects of delta9-THC, WIN 55,212-2, and CP 55,940 is more readily obtained in a variety of tests. The selective blockade of CB1 receptors by SR 141716 impaired the perception of the appetitive value of positive reinforcers (food, cocaine, morphine) and reduced the motivation for sucrose, beer and alcohol consumption, indicating that positive incentive and/or motivational processes could be under a permissive control of CB1-related mechanisms. There is little evidence that cannabinoid systems are activated under basal conditions. However, by using SR 141716 as a tool, a tonic involvement of a CB1-mediated cannabinoid link has been demonstrated, notably in animals suffering from chronic pain, faced with anxiogenic stimuli or highly motivational reinforcers. Some effects of SR 141716 also suggest that CB1-related mechanisms exert a tonic control on cognitive processes. Extensive basic research is still needed to elucidate the roles of cannabinoid systems, both in the brain and at the periphery, in normal physiology and in diseases. Additional compounds, such as selective CB1 receptor agonists, ligands that do not cross the blood brain barrier, drugs interfering with synthesis, degradation or uptake of endogenous ligand(s) of CB receptors, are especially needed to understand when and how cannabinoid systems are activated. In turn, new therapeutic strategies would likely to emerge.

Animals↗

PubMed2000

Involvement of cannabinoid receptors in the intraocular pressure-lowering effects of WIN55212-2.

It is known that marijuana smoking and administration of natural cannabinoids reduce intraocular pressure. However, it has not been established whether the intraocular pressure-lowering effects of cannabinoids are mediated by cannabinoid receptors. Aminoalkylindoles are a new class of cannabimimetics with structures entirely different from those of natural cannabinoids. WIN55212-2, a prototypic aminoalkylindole, has been shown to bind cannabinoid receptors and to exhibit cannabinoid-like activities. The objective of this study was to determine whether aminoalkylindoles lower intraocular pressure and whether the effects of aminoalkylindoles are mediated by ocular cannabinoid receptors. The intraocular pressure of New Zealand White rabbits was measured with the use of applanation pneumatonography. After the measurement of baseline intraocular pressure, drugs were applied topically and the intraocular pressure was monitored. The topical application of WIN55212-2 significantly reduced intraocular pressure in the treated eyes. The intraocular pressure-lowering effects of WIN55212-2 were time and dose dependent, and the maximal reduction was 4.7 +/- 0.5 mm Hg at a dose of 100 microg. In contrast to treated eyes, the intraocular pressure on the contralateral eyes was not significantly affected. The topical application of WIN55212-3, the enantiomer of WIN55212-2, had no effect on intraocular pressure. Furthermore, the intraocular pressure-lowering effects of WIN55212-2 were significantly reduced by topically administered SR141716A, a selective antagonist for the CB1 cannabinoid receptor. The dose-response curve of WIN55212-2 is shifted parallel to the right by SR141716A. These data demonstrate that like natural cannabinoids, WIN55212-2 also reduces intraocular pressure, and the effects of WIN55212-2 are mediated at least in part by the CB1 cannabinoid receptors in the eye.

Administration, Topical↗

PubMed2000

Cannabinoids decrease the K(+) M-current in hippocampal CA1 neurons.

Cannabinoid effects on sustained conductances that control neuronal excitability have not been investigated in brain. Here, intracellular voltage-clamp recordings were performed using the rat hippocampal slice preparation to study the postsynaptic effect of cannabinoid agonists on CA1 pyramidal neurons. Superfusion of the cannabimimetics WIN55212-2 or methanandamide onto CA1 neurons elicited an inward steady-state current that reversed near the equilibrium potential for K(+) and voltage-dependently activated from a threshold of approximately -70 mV. The cannabinoid receptor (CB1) antagonist SR141716 did not alter membrane properties but prevented this effect. Further investigation revealed that the inward current elicited by cannabinoids was caused by a decrease of the noninactivating voltage-dependent K(+) M-current (I(M)). Cannabinoids had no effect in slices pretreated with the M-channel blocker linopirdine. Assessment of the I(M) relaxation indicated that cannabinoids decreased I(M) in a concentration-dependent manner, with a maximum inhibition of 45 +/- 3% with WIN55212-2 (EC(50) of 0. 6 microM) and 41 +/- 5% with methanandamide (EC(50) of 1 microM). Cannabinoids did not affect the inwardly rectifying cationic h-current (I(h)). The cannabinoid-induced I(M) decrease was prevented by SR141716 but remained unaffected by the muscarinic receptor antagonist atropine. Conversely, the cholinergic agonist carbamylcholine decreased I(M) in the presence of SR141716, indicating that cannabinoid and muscarinic receptor activation independently diminish I(M). It is concluded that cannabinoids may postsynaptically augment the excitability of CA1 pyramidal neurons by specifically decreasing the persistent voltage-dependent I(M).

Animals↗

PubMed2000

Actions of cannabinoids on membrane properties and synaptic transmission in rat periaqueductal gray neurons in vitro.

The midbrain periaqueductal gray (PAG) is a major site of cannabinoid-mediated analgesia in the central nervous system. In the present study, we examined the actions of cannabinoids on rat PAG neurons in vitro. In brain slices, superfusion of the cannabinoid receptor agonist WIN55,212-2 inhibited electrically evoked inhibitory and excitatory postsynaptic currents in all PAG neurons. The endogenous cannabinoid anandamide inhibited evoked inhibitory postsynaptic currents in the presence of the anandamide transport inhibitor AM404, but not in its absence. The stable anandamide analog R1-methanandamide also inhibited evoked inhibitory postsynaptic currents. WIN55,212-2 reduced the rate of spontaneous miniature inhibitory postsynaptic currents in normal and Ca(2+)-free solutions, but had no effect on their amplitude distributions or kinetics. The WIN55,212-2-induced decrease in miniature inhibitory postsynaptic current rate was concentration dependent (EC(50) = 520 nM). The effects of cannabinoids were reversed by the CB(1) receptor antagonist SR141716. WIN55,212-2 produced no change in membrane current or conductance in PAG neurons in brain slices and had no effect on Ca(2+)-channel currents in acutely isolated PAG neurons. These findings suggest that cannabinoids act via CB(1) receptors to inhibit GABAergic and glutamatergic synaptic transmission in rat PAG, although the efficacy of endogenous cannabinoids is likely to be limited by uptake and breakdown. Like mu-opioids, cannabinoids act to reduce the probability of transmitter release from presynaptic terminals via a Ca(2+)-independent mechanism. In contrast to mu-opioids, cannabinoids have no direct postsynaptic actions on PAG neurons. Thus, cannabinoids and mu-opioids are likely to produce analgesia within PAG in part by different mechanisms.

Animals↗

PubMed2005

Recent developments in the therapeutic potential of cannabinoids.

OBJECTIVE: To examine the recent evidence that marijuana and other cannabinoids have therapeutic potential. METHODS: Literature published since 1997 was searched using the following terms: cannabinoid, marijuana, THC, analgesia, cachexia, glaucoma, movement, multiple sclerosis, neurological, pain, Parkinson, trial, vomiting. Qualifying clinical studies were randomized, double-blind, and placebo-controlled. Selected open-label studies and surveys are also discussed. RESULTS: A total of 15 independent, qualifying clinical trials were identified, of which only three had more than 100 patients each. Two large trials found that cannabinoids were significantly better than placebo in managing spasticity in multiple sclerosis. Patients self-reported greater sense of motor improvement in multiple sclerosis than could be confirmed objectively. In smaller qualifying trials, cannabinoids produced significant objective improvement of tics in Tourette's disease, and neuropathic pain. A new, non-psychotropic cannabinoid also has analgesic activity in neuropathic pain. No significant improvement was found in levodopa-induced dyskinesia in Parkinson's Disease or post-operative pain. No difference from active placebo was found for management of cachexia in a large trial. Some immune system parameters changed in HIV-1 and multiple sclerosis patients treated with cannabinoids, but the clinical significance is unknown. Quality of life assessments were made in only three of 15 qualifying clinical trials. CONCLUSION: Cannabinoids may be useful for conditions that currently lack effective treatment, such as spasticity, tics and neuropathic pain. New delivery systems for cannabinoids and cannabis-based medicinal extracts, as well as new cannabinoid derivatives expand the options for cannabinoid therapy. More well-controlled, large clinical tests are needed, especially with active placebo.

Cannabinoids↗

PubMed1986

Cellular effects of cannabinoids.

The many studies that have been included in this review suggest that cannabinoids have ubiquitous effects on biological systems. These results also underscore the intensity to which cannabinoids have been studied. While there are numerous reasons for the prodigious amount of cannabinoid research, a major stimulus has been the desire to identify a specific biochemical event or pathway that is responsible for the expression of delta 9-THC's unique psychoactivity. It is the hope that delta 9-THC, as with all centrally acting drugs, might serve as an important tool for achieving a better understanding of the central nervous system. As discussed in this review, the psychoactivity of cannabinoids might best be described as a composite of numerous effects. If that is indeed the case, then it would seem logical that these centrally mediated effects do not arise from a single biochemical alteration, but rather from multiple actions. Of course, a major problem arises when one attempts to establish a relationship between cause and effect when multiple mechanisms and effects are involved. An initial approach to reducing the complexity of elucidation of mechanism of action should involve attempts to distinguish those cannabinoid actions which result in specific effects (psychoactivity) from those which produce non-psychoactive effects (such as general depression). There are several fundamental principles that can be used to assess specificity, including concentration or dose of the drug that is required to produce a given effect. Low doses of delta 9-THC are capable of producing the psychoactivity that is unique to cannabinoids, whereas higher doses may produce effects that are both specific and nonspecific for cannabinoids. Unfortunately, establishing this basic tenet for delta 9-THC has proven to be difficult. It has not been possible to establish the concentration of delta 9-THC at its site of action that is necessary to produce a given pharmacological effect. While it is a simple matter to measure the concentration of cannabinoids in either a whole tissue or an incubation medium, the hydrophobicity of cannabinoids dramatically affects their affinity for, and hence concentration in, the biochemical components of the tissue. If the concentration of delta 9-THC could be measured at its site of action, then the relevance of many of its pharmacological effects could be adequately determined. Two possible mechanisms by which cannabinoids might produce psychoactivity are membrane perturbation and receptor interactions, and indeed, both mechanisms have received considerable attention.(ABSTRACT TRUNCATED AT 400 WORDS)

Adenosine Triphosphatases↗

PubMedDate not supplied

Cardiovascular actions of cannabinoids and their generation during shock.

Marijuana is a widely abused recreational drug well known for its psychoactive properties. Cannabinoids, the active ingredients of marijuana, elicit their neurobehavioral effects by interacting with the CB1 cannabinoid receptor subtype, expressed primarily in the brain but also present in some peripheral tissues. A second receptor subtype, the CB2 receptor, is expressed on cells of the immune system and is thought to be responsible for the immunosuppressant effects of cannabinoids. Recently, endogenous lipidlike substances have been identified, including arachidonyl ethanolamide (anandamide) and 2-arachidonyl glyceride, that bind to cannabinoid receptors and mimic many of the neurobehavioral effects of plant-derived cannabinoids. Both plant-derived cannabinoids and the endogenous ligands have been shown to elicit hypotension and bradycardia via activation of peripherally located CB1 receptors. Possible underlying mechanisms include presynaptic CB1 receptor mediated inhibition of norepinephrine release from peripheral sympathetic nerve terminals, and/or direct vasodilation via activation of vascular cannabinoid receptors. The latter may also be the target of endocannabinoids of vascular endothelial origin. Recent studies indicate that a peripheral endogenous cannabinoid system in circulating macrophages and platelets is activated in hemorrhagic and septic shock and may contribute to the hypotension associated with these conditions via activation of vascular cannabinoid receptors. The potential role of this mechanism in human shock conditions is under investigation.

Animals↗

PubMed2000

Pharmacological characterisation of cannabinoid CB(1) receptors in the rat and mouse.

The role of cannabinoid CB(1) receptors in sympathetic neurotransmission was characterised in nerve-mediated responses of isolated right atria, vasa deferentia and small mesenteric resistance arteries using the cannabinoid CB(1) receptor agonists Delta(9)-tetrahydrocannabinol, CP 55,940 and anandamide and the cannabinoid CB(1)-selective antagonist SR 141716A. In the mouse vas deferens, the twitch response was completely inhibited by each of the putative cannabinoid receptor agonists with pIC(50) values of CP 55,940, 9.2+/-0.1; Delta(9)-tetrahydrocannabinol, 8.4+/-0.1; anandamide, 7.1+/-0.1. SR 141716A 10-100 nM was a competitive antagonist of all three agonists with a pK(B) value of 8.4-8.6, consistent with an interaction at the cannabinoid CB(1) receptor. In the rat vas deferens CP 55,940 (0.01-10 microM) inhibited the contractions to a significant extent (88.5+/-0.5% at 10 microM; pIC(50) of 7.1+/-0.1) while Delta(9)-tetrahydrocannabinol and anandamide (both up to 10 microM) were inactive. CP 55,940 exhibited low potency in rat compared with mouse vas deferens and the rat concentration-response curve was not competitively antagonised by SR 141716A (100 nM) or SR 144528 (10 nM-10 microM), suggesting an interaction at a receptor(s) distinct from cannabinoid CB(1) or CB(2). Sympathetic nerve-induced tachycardia in rat and mouse atria, and rat mesenteric artery smooth muscle contractile responses to perivascular nerve stimulation, were not inhibited by Delta(9)-tetrahydrocannabinol, CP 55,940 or anandamide up to 1 microM. These data indicate that cannabinoid CB(1) receptor activation inhibits sympathetic neurotransmission only in the mouse vas deferens and thus point to species and regional differences in cannabinoid CB(1) receptor involvement in pre-synaptic inhibition of sympathetic neurotransmission and CP 55,940 may have inhibitory actions in rat vas deferens unrelated to cannabinoid receptor activity.

Animals↗

PubMed2002

Endocannabinoids and cannabinoid receptor genetics.

This review presents the remarkable advances that have been achieved in marijuana (cannabinoid) research, with the discovery of specific receptors and the existence of naturally occurring cannabis-like substances in the human body and brain. The last decade has seen more rapid progress in marijuana research than any time in the thousands of years that marijuana has been used by humans, particularly in cannabinoid genomics. The cDNA and genomic sequences encoding G protein-coupled cannabinoid receptors (Cnrs) from several species have now been cloned. Endogenous cannabinoids (endocannabinoids), synthetic and hydrolyzing enzymes and transporters that define neurochemically-specific cannabinoid brain pathways have been identified. Endocannabinoid lipid signaling molecules alter activity at G protein-coupled receptors (GPCR) and possibly at anandamide-gated ion channels, such as vanilloid receptors. Availability of increasingly-specific CB1 and CB2 Cnr antagonists and of CB1 and CB2 Cnr knockout mice have increased our understanding of these cannabinoid systems and provides tantalizing evidence for even more G protein-coupled Cnrs. Initial studies of the Cnr gene structure, regulation and polymorphisms whet our appetite for more information about these interesting genes, their variants and roles in vulnerabilities to addictions and other neuropsychiatric disorders. Behavioral studies of cannabinoids document the complex interactions between rewarding and aversive effects of these drugs. Pursuing cannabinoid-related molecular, pharmacological and behavioral leads will add greatly to our understanding of endogenous brain neuromodulator systems, abused substances and potential therapeutics. This review of CB1 and CB2 Cnr genes in human and animal brain and their neurobiological effects provide a basis for many of these studies. Therefore, understanding the physiological cannabinoid control system in the human body and brain will contribute to elucidating this natural regulatory mechanism in health and disease.

Amino Acid Sequence↗

PubMed2006

Behavioral methods in cannabinoid research.

In the absence of any specific behavioral assay for cannabinoids or endocannabinoids, a cannabinoid-induced profile in a series of four in vivo assays in mice is most commonly used to assess a specific cannabinoid activity at the behavioral level. Thus, when a given compound produces motor depression in an open field, catalepsy on an elevated ring, analgesia on a hot plate, as well as hypothermia, cannabinoid CB1 receptor activation is assumed, although exceptions are possible. The full cannabinoid profile, however, includes for example ataxia in dogs and discrimination learning in rats. In view of (1) the addictive/reward potential of cannabis and the cannabinoids and (2) the multiple roles of the endocannabinoid physiological control system (EPCS) in behavioral functions, including memory, emotionality, and feeding, a number of behavioral techniques have been used to assess the effects of cannabinoids in these functions. In this chapter we will describe the tetrad of cannabinoid-induced effects as well as a series of behavioral assays used in the behavioral pharmacology of marijuana-cannabinoid research. Since the EPCS plays an important role in the developing organism, methods used in the assessment of physical and behavioral development will also be discussed. The techniques include the tetrad, drug discrimination, self-stimulation and self-administration, conditioned place preference/aversion, the plus-maze, chronic mild stress (CMS), ultrasonic vocalizations, cognitive behaviors, and developmental assessment in mouse (and rat) pups.

Animals↗

PubMed1995

Evaluation of cAMP involvement in cannabinoid-induced antinociception.

It has been proposed that cannabinoids act at a Gi protein-coupled receptor to produce antinociception. One action of Gi-proteins is to decrease intracellular cAMP via inhibition of adenylyl cyclase activity. Although cannabinoid inhibition of forskolin-stimulated adenylyl cyclase is used as a confirmation of functional cannabinoid receptors, it is unknown whether this second messenger system specifically mediates cannabinoid-induced antinociception. This in vivo study was conducted using enantiomeric cAMP analogs, Rp-cAMPS (an antagonist) and Sp-cAMPS (an agonist), and the cAMP agonist Cl-cAMP to test the hypothesis that cannabinoid-induced antinociception is due to decreased adenylyl cyclase activity. None of the cAMP analogs, forskolin, or 1,9-dideoxy-forskolin affected delta 9-THC or CP-55,940-induced antinociception produced by intrathecal (i.t.) or intracerebroventricular (i.c.v.) injections in mice. Experiments were also conducted to investigate whether i.c.v. administration of Sp-cAMPS would block i.c.v. cannabinoid-induced antinociception in rats. Sp-cAMPS failed to block CP-55,940-induced antinociception. However, Sp-cAMPS produced hyper-excitability and reactive behavior indicating that it did elicit a pharmacological effect. Although, adenylyl cyclase may mediate other cannabinoid-induced actions, these results do not support the hypothesis that it is involved in cannabinoid-induced antinociception. Alternatively, other effector systems such as calcium or potassium channels coupled to cannabinoid receptors may mediate cannabinoid-induced antinociception.

Analgesics↗

PubMed2001

Cannabinoid receptor agonist and antagonist effects on motor function in normal and 1-methyl-4-phenyl-1,2,5,6-tetrahydropyridine (MPTP)-treated non-human primates.

RATIONALE: Although cannabinoid effects on motor function have been extensively studied in rodents, the role of cannabinoids in regulating behavior in primates is relatively unknown. OBJECTIVES: We compared the effects of cannabinoid agonists and dopamine antagonists on unconditioned behaviors in cynomolgus monkeys (Macaca fascicularis). We further investigated the therapeutic potential of cannabinoid antagonists in a primate model of Parkinson's disease. METHODS: Drugs were administered i.m., and sessions were videotaped and rated by a "blind" observer using a rating scale. RESULTS: The dopamine antagonist haloperidol decreased locomotor activity and increased bradykinesia in three subjects. Haloperidol also produced a dose-dependent increase in freezing and catalepsy in two out of the three subjects. The cannabinoid agonist levonantradol dose-dependently decreased general and locomotor activity and increased bradykinesia. In contrast to haloperidol, levonantradol failed to produce freezing or catalepsy. At the dose range studied, tetrahydrocannabinol did not affect general or locomotor activity, but increased bradykinesia. In view of the psychomotor slowing induced by cannabinoid agonists, we investigated the therapeutic potential of the cannabinoid receptor antagonist SR141716A in an early and advanced stage of 1-methyl-4-phenyl-1,2,5,6-tetrahydropyridine-induced parkinsonism. In both models of Parkinson's disease, SR141716A failed to alleviate the motor deficits of parkinsonism. CONCLUSIONS: Cannabinoid agonists do not induce catalepsy in primates, a finding that differs from their effects in rodents. The primate may be more suitable than rodents for predicting the effects of cannabinoids and their therapeutic potential on select primate behaviors.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗

PubMed2004

[Review of cannabinoids in the treatment of nausea and vomiting].

Cannabinoids are used to treat nausea and vomiting. The effect appears to be mediated by cannabinoid receptors in the nucleus tractus solitarius. Results are available from studies on the use of cannabinoids to manage nausea and vomiting after chemotherapy. None of these studies, however, compared cannabinoids with the newer serotonin antagonists. The antiemetic efficacy of cannabinoids for other indications has not yet been studied sufficiently. Most of the studies report significantly more or stronger side effects with cannabinoid medication in comparison to similar medication. In some of the studies on treatment after chemotherapy or radiotherapy, the patients terminated the cannabinoid therapy more frequently due to side effects. Although clinical studies have provided clear evidence for the antiemetic efficacy of cannabinoids, the frequency and severity of side effects argue against their use as the method of first choice. For patients who cannot be adequately treated with conventional antiemetic agents, cannabinoids can represent a valuable adjunct to the antiemetic regimen.

Antiemetics↗

PubMed2006

Cannabinoids inhibit human keratinocyte proliferation through a non-CB1/CB2 mechanism and have a potential therapeutic value in the treatment of psoriasis.

BACKGROUND: Cannabinoids from cannabis (Cannabis sativa) are anti-inflammatory and have inhibitory effects on the proliferation of a number of tumorigenic cell lines, some of which are mediated via cannabinoid receptors. Cannabinoid (CB) receptors are present in human skin and anandamide, an endogenous CB receptor ligand, inhibits epidermal keratinocyte differentiation. Psoriasis is an inflammatory disease also characterised in part by epidermal keratinocyte hyper-proliferation. OBJECTIVE: We investigated the plant cannabinoids Delta-9 tetrahydrocannabinol, cannabidiol, cannabinol and cannabigerol for their ability to inhibit the proliferation of a hyper-proliferating human keratinocyte cell line and for any involvement of cannabinoid receptors. METHODS: A keratinocyte proliferation assay was used to assess the effect of treatment with cannabinoids. Cell integrity and metabolic competence confirmed using lactate-dehydrogenase and adenosine tri-phosphate assays. To determine the involvement of the receptors, specific agonist and antagonist were used in conjunction with some phytocannabinoids. Western blot and RT-PCR analysis confirmed presence of CB1 and CB2 receptors. RESULTS: The cannabinoids tested all inhibited keratinocyte proliferation in a concentration-dependent manner. The selective CB2 receptor agonists JWH015 and BML190 elicited only partial inhibition, the non-selective CB agonist HU210 produced a concentration-dependent response, the activity of theses agonists were not blocked by either CB1/CB2 antagonists. CONCLUSION: The results indicate that while CB receptors may have a circumstantial role in keratinocyte proliferation, they do not contribute significantly to this process. Our results show that cannabinoids inhibit keratinocyte proliferation, and therefore support a potential role for cannabinoids in the treatment of psoriasis.

Analgesics, Non-Narcotic↗

PubMed2001

Assessment of the role of CB1 receptors in cannabinoid anticonvulsant effects.

The cannabinoid CB1 receptor has been shown to be the primary site of action for cannabinoid-induced effects on the central nervous system. Activation of this receptor has proven to dampen neurotransmission and produce an overall reduction in neuronal excitability. Cannabinoid compounds like delta9-tetrahydrocannabinol and cannabidiol have been shown to be anticonvulsant in maximal electroshock, a model of partial seizure with secondary generalization. However, until now, it was unknown if these anticonvulsant effects are mediated by the cannabinoid CB1 receptor. Likewise, (R)-(+)-[2,3-Dihydro-5-methyl-3-(4-morpholinylmethyl)pyrrolo[1,2,3-de]-1,4-benzoxazin-6-yl]-1-naphthalenylmethanone (WIN 55,212-2), a cannabimimetic compound that has been shown to decrease hyperexcitability in cell culture models via the cannabinoid CB1 receptor, has never been evaluated for anticonvulsant activity in an animal seizure model. We first show that the cannabinoid compounds delta9-tetrahydrocannabinol (ED50 = 42 mg/kg), cannabidiol (ED50 = 80 mg/kg), and WIN 55,212-2 (ED50 = 47 mg/kg) are anticonvulsant in maximal electroshock. We further establish, using the cannabinoid CB1 receptor specific antagonist N-(piperidin-1-yl-5-(4-chlorophenyl)-1-(2,4-dichlorophenyl)-4-methyl-1H-pyrazole-3-carboxamidehydrochloride (SR141716A) (AD50 = 2.5 mg/kg), that the anticonvulsant effects of delta9-tetrahydrocannabinol and WIN 55,212-2 are cannabinoid CB1 receptor-mediated while the anticonvulsant activity of cannabidiol is not. This study establishes a role for the cannabinoid CB1 receptor in modulating seizure activity in a whole animal model.

Animals↗

PubMed2003

Milk intake and survival in newborn cannabinoid CB1 receptor knockout mice: evidence for a "CB3" receptor.

Cannabinoids, whether plant-derived, synthetic or endogenous, have been shown to stimulate appetite in the adult organism. We have reported previously that cannabinoid receptors play a critical role during the early suckling period: The selective cannabinoid CB(1) receptor antagonist N-(piperidiny-1-yl)-5-(4-chlorophenyl)-1-(2,4-dichlorophenyl)-4-methyl-1H-pyrazole-3-carboxamide (SR141617A) permanently prevented milk ingestion in a dose-dependent manner, when administered to (Sabra, albino) mouse pups, within 1 day of birth. As a consequence, these pups died within the first week of life. We now generalize this finding to a different strain of mice (C57BL/6). Further, we show that cannabinoid CB(1) receptor blockade (20 mg/kg SR141716A) must occur within 24 h after birth as injection of SR141716A into 2- or 5-day-old pups had a much smaller effect or no effect at all, respectively. Cannabinoid CB(1) receptor knockout mice did not ingest milk on the first day of life, similarly to SR141716A-treated normal pups, as measured by the appearance of "milkbands". However, the knockout pups started to display milkbands from day 2 of life. Survival rates of cannabinoid CB(1) receptor knockout mice were affected significantly, but to a lesser extent than normal pups, by the administration of SR141716A. Daily administration of the endocannabinoid 2-arachidonoyl glycerol, or the synthetic agonists (R)-(+)-[2,3-dihydro-5-methyl-3-(4-morpholinylmethyl)pyrrolo[1,2,3-de]-1,4-benzoxazin-6-yl]-1-naphthalenylmethanone (WIN55,212-2, 5 mg/kg) or (-)-cis-3-[2-Hydroxy4-(1,1-dimethylheptyl) phenyl]-trans-4-(3-hydroxypropyl)cyclohexanol (CP55,940, 5 or 20 mg/kg) did not promote survival or weight gain in CB(1)(-/-) pups. Our data support previous evidence for a critical role of cannabinoid CB(1) receptors for the initiation of suckling. Further, the present observations support the existence of an unknown cannabinoid receptor, with partial control over milk ingestion in newborns. Our data also suggest that the CB(1)(-/-) neonates possess a compensatory mechanism which helps them overcome the lack of cannabinoid CB(1) receptors.

Animals↗