The presence and function of CB2 receptors in central nervous system (CNS) neurons are controversial. We report the expression of CB2 receptor messenger RNA and protein localization on brainstem neurons. These functional CB2 receptors in the brainstem were activated by a CB2 receptor agonist, 2-arachidonoylglycerol, and by elevated endogenous levels of endocannabinoids, which also act at CB1 receptors. CB2 receptors represent an alternative site of action of endocannabinoids that opens the possibility of nonpsychotropic therapeutic interventions using enhanced endocannabinoid levels in localized brain areas.

Based upon evidence that the therapeutic properties of Cannabis preparations are not solely dependent upon the presence of Δ 9 -tetrahydrocannabinol (THC), pharmacological studies have been recently carried out with other plant cannabinoids (phytocannabinoids), particularly cannabidiol (CBD) and Δ 9 -tetrahydrocannabivarin (THCV). Results from some of these studies have fostered the view that CBD and THCV modulate the effects of THC via direct blockade of cannabinoid CB1 receptors, thus behaving like first-generation CB1 receptor inverse agonists, such as rimonabant. Here, we review in vitro and ex vivo mechanistic studies of CBD and THCV, and synthesize data from these studies in a meta-analysis. Synthesized data regarding mechanisms are then used to interpret results from recent pre-clinical animal studies and clinical trials. The evidence indicates that CBD and THCV are not rimonabant-like in their action and thus appear very unlikely to produce unwanted CNS effects. They exhibit markedly disparate pharmacological profiles particularly at CB1 receptors: CBD is a very low-affinity CB1 ligand that can nevertheless affect CB1 receptor activity in vivo in an indirect manner, while THCV is a high-affinity CB1 receptor ligand and potent antagonist in vitro and yet only occasionally produces effects in vivo resulting from CB1 receptor antagonism. THCV has also high affinity for CB2 receptors and signals as a partial agonist, differing from both CBD and rimonabant. These cannabinoids illustrate how in vitro mechanistic studies do not always predict in vivo pharmacology and underlie the necessity of testing compounds in vivo before drawing any conclusion on their functional activity at a given target.

BACKGROUND AND PURPOSEPhytocannabinoids in Cannabis sativa have diverse pharmacological targets extending beyond cannabinoid receptors and several exert notable anticonvulsant effects. For the first time, we investigated the anticonvulsant profile of the phytocannabinoid cannabidivarin (CBDV) in vitro and in in vivo seizure models. EXPERIMENTAL APPROACHThe effect of CBDV (1-100 mM) on epileptiform local field potentials (LFPs) induced in rat hippocampal brain slices by 4-aminopyridine (4-AP) application or Mg 2+ -free conditions was assessed by in vitro multi-electrode array recordings. Additionally, the anticonvulsant profile of CBDV (50-200 mg·kg -1 ) in vivo was investigated in four rodent seizure models: maximal electroshock (mES) and audiogenic seizures in mice, and pentylenetetrazole (PTZ) and pilocarpine-induced seizures in rats. The effects of CBDV in combination with commonly used antiepileptic drugs on rat seizures were investigated. Finally, the motor side effect profile of CBDV was investigated using static beam and grip strength assays. KEY RESULTS CBDV significantly attenuated status epilepticus-like epileptiform LFPs induced by 4-AP and Mg 2+-free conditions. CBDV had significant anticonvulsant effects on the mES (Ն100 mg·kg ) alone had no effect against pilocarpine-induced seizures, but significantly attenuated these seizures when administered with valproate or phenobarbital at this dose. CBDV had no effect on motor function. CONCLUSIONS AND IMPLICATIONSThese results indicate that CBDV is an effective anticonvulsant in a broad range of seizure models. Also it did not significantly affect normal motor function and, therefore, merits further investigation as a novel anti-epileptic in chronic epilepsy models. LINKED ARTICLESThis article is part of a themed section on Cannabinoids. To view the other articles in this section visit http://dx

The emerging potential for the cannabinoid (CB) system in modulating gastrointestinal inflammation has gained momentum over the last few years. Traditional and anecdotal use of marijuana for gastrointestinal disorders, such as diarrhoea and abdominal cramps is recognized, but the therapeutic benefit of cannabinoids in the 21st century is overshadowed by the psychoactive problems associated with CB 1 receptor activation. However, the presence and function of the CB 2 receptor in the GI tract, whilst not yet well characterized, holds great promise due to its immunomodulatory roles in inflammatory systems and its lack of psychotropic effects. This review of our current knowledge of CB 2 receptors in the gastrointestinal tract highlights its role in regulating abnormal motility, modulating intestinal inflammation and limiting visceral sensitivity and pain. CB 2 receptors represent a braking system and a pathophysiological mechanism for the resolution of inflammation and many of its symptoms. CB 2 receptor activation therefore represents a very promising therapeutic target in gastrointestinal inflammatory states where there is immune activation and motility dysfunction.

SUMMARYThe therapeutic actions of cannabinoids have been known for centuries. In the last 25 years this area of research has grown exponentially with the discovery of specific cannabinoid receptors and endogenous ligands.In the enteric nervous system of gastrointestinal tract, cannabinoid receptors are located on enteric nerve terminals where they exert inhibitory actions on neurotransmission to reduce motility and secretion. Endogenous cannabinoids are present in the enteric nervous system, as are the degradative enzymes necessary to inhibit their action. The cellular mechanism of action of endocannabinoids has not been established in the enteric nervous system. Endocannabinoids not only act at cannabinoid receptors, but potentially also at vanilloid and 5-HT 3 receptors, both of which are expressed in the gastrointestinal tract. The interactions between endocannabinoids and these other important receptor systems have not been extensively investigated. A greater understanding of the endocannabinoid system in the enteric nervous system could lead to advances with important therapeutic potential in the treatment of gastrointestinal disorders such as irritable bowel syndrome, inflammatory bowel disease, secretory diarrhoea and gastro-oesophageal reflux disease. INTRODUCTIONCannabis, marijuana, hashish and their derivatives have been known for centuries to stimulate appetite, inhibit emesis, normalize gastrointestinal motility and improve a variety of other gastrointestinal conditions. 1 With the discovery in the early 1960s that D 9 -tetrahydrocannabinol (THC) was the main psychoactive constituent of cannabis, 2 considerable efforts were made to understand the biology of this class of compounds. This ultimately led to the discovery of two specific cannabinoid (CB) receptors, 3, 4 termed CB 1 and CB 2 receptors and the search and identification of endogenous CB ligands, anandamide and 2-arachidonylglycerol (2-AG). [5][6][7] It is now clear that the gastrointestinal tract contains an endocannabinoid system where endocannabinoids are synthesized locally and act on specific receptors modulating a variety of functions.In this short review we describe the endocannabinoid system in relation to the enteric nervous system (ENS). The ENS is the major site of action of CBs in the gastrointestinal tract. 8,9 The ENS is composed of nerve fibres that innervate the tissues of the gut and neurones that are found in two major plexuses: the myenteric plexus that lies between the external muscle layers and the submucosal plexus that is located in the submucosa. 10 Besides being an autonomous control system, the ENS is also the final pathway for central nervous system (CNS) regulation of gastrointestinal function. Cannabinoids act at many points within the brain-gut

Enhanced intestinal transit due to lipopolysaccharide (LPS) is reversed by cannabinoid (CB)2 receptor agonists in vivo, but the site and mechanism of action are unknown. We have tested the hypothesis that CB2 receptors are expressed in the enteric nervous system and are activated in pathophysiological conditions. Tissues from either saline- or LPS-treated (2 h; 65 microg/kg ip) rats were processed for RT-PCR, Western blotting, and immunohistochemistry or were mounted in organ baths where electrical field stimulation was applied in the presence or absence of CB receptor agonists. Whereas the CB2 receptor agonist JWH133 did not affect the electrically evoked twitch response of the ileum under basal conditions, in the LPS-treated tissues JWH133 was able to reduce the enhanced contractile response in a concentration-dependent manner. Rat ileum expressed CB2 receptor mRNA and protein under physiological conditions, and this expression was not affected by LPS treatment. In the myenteric plexus, CB2 receptors were expressed on the majority of neurons, although not on those expressing nitric oxide synthase. LPS did not alter the distribution of CB2 receptor expression in the myenteric plexus. In vivo LPS treatment significantly increased Fos expression in both enteric glia and neurons. This enhanced expression was significantly attenuated by JWH133, whose action was reversed by the CB2 receptor antagonist AM630. Taking these facts together, we conclude that activation of CB2 receptors in the enteric nervous system of the gastrointestinal tract dampens endotoxin-induced enhanced intestinal contractility.

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BACKGROUND AND PURPOSEEpilepsy is the most prevalent neurological disease and is characterized by recurrent seizures. Here, we investigate (i) the anticonvulsant profiles of cannabis-derived botanical drug substances (BDSs) rich in cannabidivarin (CBDV) and containing cannabidiol (CBD) in acute in vivo seizure models and (ii) the binding of CBDV BDSs and their components at cannabinoid CB1 receptors. EXPERIMENTAL APPROACHThe anticonvulsant profiles of two CBDV BDSs (50-422 mg·kg −1 ) were evaluated in three animal models of acute seizure. Purified CBDV and CBD were also evaluated in an isobolographic study to evaluate potential pharmacological interactions. CBDV BDS effects on motor function were also investigated using static beam and grip strength assays. Binding of CBDV BDSs to cannabinoid CB1 receptors was evaluated using displacement binding assays. KEY RESULTSCBDV BDSs exerted significant anticonvulsant effects in the pentylenetetrazole (≥100 mg·kg ). The isobolographic study revealed that the anticonvulsant effects of purified CBDV and CBD were linearly additive when co-administered. Some motor effects of CBDV BDSs were observed on static beam performance; no effects on grip strength were found. The Δ 9 -tetrahydrocannabinol and Δ 9 -tetrahydrocannabivarin content of CBDV BDS accounted for its greater affinity for CB1 cannabinoid receptors than purified CBDV. CONCLUSIONS AND IMPLICATIONSCBDV BDSs exerted significant anticonvulsant effects in three models of seizure that were not mediated by the CB1 cannabinoid receptor and were of comparable efficacy with purified CBDV. These findings strongly support the further clinical development of CBDV BDSs for the treatment of epilepsy.