Raphael Mechoulam

Identification of an endogenous 2-monoglyceride, present in canine gut, that binds to cannabinoid receptors.

In this study, we report the isolation from canine intestines of 2-arachidonyl glycerol (2-Ara-Gl). Its structure was determined by mass spectrometry and by direct comparison with a synthetic sample. 2-Ara-Gl bound to membranes from cells transiently transfected with expression plasmids carrying DNA of either CB1 or CB2--the two cannabinoid receptors identified thus far--with Ki values of 472 +/- 55 and 1400 +/- 172 nM, respectively. In the presence of forskolin, 2-Ara-Gl inhibited adenylate cyclase in isolated mouse spleen cells, at the potency level of delta 9-tetrahydrocannabinol (delta 9-THC). Upon intravenous administration to mice, 2-Ara-Gl caused the typical tetrad of effects produced by THC: antinociception, immobility, reduction of spontaneous activity, and lowering of the rectal temperature. 2-Ara-Gl also shares the ability of delta 9-THC to inhibit electrically evoked contractions of mouse isolated vasa deferentia; however, it was less potent than delta 9-THC.

International Union of Pharmacology. XXVII. Classification of Cannabinoid Receptors

Two types of cannabinoid receptor have been discovered so far, CB1 (2.1: CBD:1:CB1:), cloned in 1990, and CB2(2.1:CBD:2:CB2:), cloned in 1993. Distinction between these receptors is based on differences in their predicted amino acid sequence, signaling mechanisms, tissue distribution, and sensitivity to certain potent agonists and antagonists that show marked selectivity for one or the other receptor type. Cannabinoid receptors CB1 and CB2 exhibit 48% amino acid sequence identity. Both receptor types are coupled through G proteins to adenylyl cyclase and mitogen-activated protein kinase. CB1 receptors are also coupled through G proteins to several types of calcium and potassium channels. These receptors exist primarily on central and peripheral neurons, one of their functions being to inhibit neurotransmitter release. Indeed, endogenous CB1 agonists probably serve as retrograde synaptic messengers. CB2 receptors are present mainly on immune cells. Such cells also express CB1receptors, albeit to a lesser extent, with both receptor types exerting a broad spectrum of immune effects that includes modulation of cytokine release. Of several endogenous agonists for cannabinoid receptors identified thus far, the most notable are arachidonoylethanolamide, 2-arachidonoylglycerol, and 2-arachidonylglyceryl ether. It is unclear whether these eicosanoid molecules are the only, or primary, endogenous agonists. Hence, we consider it premature to rename cannabinoid receptors after an endogenous agonist as is recommended by the International Union of Pharmacology Committee on Receptor Nomenclature and Drug Classification. Although pharmacological evidence for the existence of additional types of cannabinoid receptor is emerging, other kinds of supporting evidence are still lacking.

An endogenous cannabinoid (2-AG) is neuroprotective after brain injury

Traumatic brain injury triggers the accumulation of harmful mediators that may lead to secondary damage. Protective mechanisms to attenuate damage are also set in motion. 2-Arachidonoyl glycerol (2-AG) is an endogenous cannabinoid, identified both in the periphery and in the brain, but its physiological roles have been only partially clarified. Here we show that, after injury to the mouse brain, 2-AG may have a neuroprotective role in which the cannabinoid system is involved. After closed head injury (CHI) in mice, the level of endogenous 2-AG was significantly elevated. We administered synthetic 2-AG to mice after CHI and found significant reduction of brain oedema, better clinical recovery, reduced infarct volume and reduced hippocampal cell death compared with controls. When 2-AG was administered together with additional inactive 2-acyl-glycerols that are normally present in the brain, functional recovery was significantly enhanced. The beneficial effect of 2-AG was dose-dependently attenuated by SR-141761A, an antagonist of the CB1 cannabinoid receptor.

Chronic Administration of Cannabidiol to Healthy Volunteers and Epileptic Patients

In phase 1 of the study, 3 mg/kg daily of cannabidiol (CBD) was given for 30 days to 8 health human volunteers. Another 8 volunteers received the same number of identical capsules containing glucose as placebo in a double-blind setting. Neurological and physical examinations, blood and urine analysis, ECG and EEG were performed at weekly intervals. In phase 2 of the study, 15 patients suffering from secondary generalized epilepsy with temporal focus were randomly divided into two groups. Each patient received, in a double-blind procedure, 200-300 mg daily of CBD or placebo. The drugs were administered for along as 4 1/2 months. Clinical and laboratory examinations, EEG and ECG were performed at 15- or 30-day intervals. Throughout the experiment the patients continued to take the antiepileptic drugs prescribed before the experiment, although these drugs no longer controlled the signs of the disease. All patients and volunteers tolerated CBD very well and no signs of toxicity or serious side effects were detected on examination. 4 of the 8 CBD subjects remained almost free of convulsive crises throughout the experiment and 3 other patients demonstrated partial improvement in their clinical condition. CBD was ineffective in 1 patient. The clinical condition of 7 placebo patients remained unchanged whereas the condition of 1 patient clearly improved. The potential use of CBD as an antiepileptic drug and its possible potentiating effect on other antiepileptic drugs are discussed.

Cannabinoids: between neuroprotection and neurotoxicity.

Cannabinoids, such as the delta9-tetrahydrocannabinol (THC), present in the cannabis plant, as well as anandamide and 2-arachidonoyl glycerol, produced by the mammalian body, have been shown to protect the brain from various insults and to improve several neurodegenerative diseases. The current review summarizes the evidence for cannabinoid neuroprotection in vivo, and refers to recent in vitro studies, which help elucidate possible molecular mechanisms underlying this protective effect. Some of these mechanisms involve the activation of CB1 and CB2 cannabinoid receptors, while others are not dependent on them. In some cases, protection is due to a direct effect of the cannabinoids on neuronal cells, while in others, it results from their effects on non-neuronal elements within the brain. In many experimental set-ups, cannabinoid neurotoxicity, particularly by THC, resides side by side with neuroprotection. The current review attempts to shed light on this dual activity, and to dissociate between the two contradictory effects.

Plant cannabinoids: a neglected pharmacological treasure trove.

Most of the cannabinoids in Cannabis sativa L. have not been fully evaluated for their pharmacological activity. A publication in this issue presents evidence that a plant cannabinoid, Δ9‐tetrahydrocannabivarin is a potent antagonist of anandamide, a major endogenous cannabinoid. It seems possible that many of the non‐psychoactive constituents of this plant will be of biological interest.

Endocannabinoids affect neurological and cognitive function in thioacetamide-induced hepatic encephalopathy in mice

Endocannabinoids function as neurotransmitters and neuromodulators in the central nervous system via specific receptors and apparently have a neuroprotective role. We assumed that the endocannabinoid system could be involved in the pathogenesis of hepatic encephalopathy (HE), a neuropsychiatric syndrome due to liver disease. We used a mouse model of a thioacetamide induced fulminant hepatic failure. We found that the levels of the endocannabinoid 2-arachidonoyl-glycerol (2-AG) were elevated in the brain. Treatment with either 2-AG or with the CB1 receptor antagonist, SR141716A, improved a neurological score, activity and cognitive function. Activation of the CB2 receptor by a selective agonist, HU308, also improved the neurological score. 2-AG activity could be blocked with the specific CB2 receptor antagonist SR144528A. The CB1 receptor agonist noladin ether was inactive. We conclude that the endocannabinoid system may play an important role in the pathogenesis of HE. Modulation of this system either by exogenous agonists specific for the CB2 receptors or possibly also by antagonists to the CB1 receptors may have therapeutic potential.

Cannabinoids as therapeutics.

Cannabis in India: ancient lore and modern medicine.- Cannabinoid chemistry: an overview.- Cannabidiol as a potential medicine.- Endocannabinoids and regulation of fertility.- Cannabinoids in neurodegeneration and neuroprotection.- Role of the endocannabinoid system in learning and memory.- Cannabinoids and anxiety.- Cannabinoid targets for pain therapeutics.- Potential use of cannabimimetics in the treatment of cancer.- Cannabinoids: effects on vomiting and nausea in animal models.- The skeleton: stone bones and stoned heads?.- Cannabinoids and drugs of abuse.- Cannabinoids in appetite and obesity.- The development of Sativex(R) - a natural cannabis-based medicine.

Towards cannabinoid drugs.

Publisher Summary This chapter discusses cannabinoid drugs. Because of its psychotropic properties, Cannabis sativa was one of the first plants to be used by man, both in social-religious rites and in medicine. Many of the actions produced by Cannabis are undoubtedly distinct from the placebo effect, and in recent years, some have been confirmed in animals and in man. The chapter compares past use with modern data to present an overview of modern use and developments and to predict future pathways in medicinal chemistry research in this area. The following abbreviations are used: THC (tetrahydrocannabinol), CBD (cannabidiol), CBN (cannabinol), DMH (1,l-dimethylheptyl), SAR (structure–activity relationship), cisplatin (cis-diamminedichloroplatinum(II)), GABA (γ-aminobutyric acid), MES (maximal electroshock seizures), PTZ (pentylenetetrazol), AGS (audiogenic seizure), IOP (intraocular pressure). It is probably impossible for man today to comprehend fully the attitudes of an ancient population toward drugs and their associations with beliefs, religion, superstitions, and social life and interactions. Cannabis oil and leaf juice were employed externally for various skin diseases, wounds, and even in leprosy. The topical antibiotic properties of cannabinoids as known today justify the use in appropriate skin diseases. Cannabis was also used against vomiting. This use was widespread in India as well.

Stereospecific Effects of (–)- and (+)-7-Hydroxy-Delta-6-Tetrahydrocannabinol-Dimethylheptyl on the Immune System of Mice

The effects of the (+) and (-) cannabinoid enantiomers 7-hydroxy-delta-6-tetra-hydrocannabinol-dimethylheptyl [(-)-7-OH-delta-6-THC-DMH (HU-210) and (+)-7-OH-delta-6-THC-DMH (HU-211)] on the inductive and productive phases of the primary humoral immune response to sheep red blood cell immunization were investigated in mice. Animals treated with (-)-7-OH-delta-6-THC-DMH (0.01, 0.05, 0.1 and 0.5 mg/kg) exhibited a dose-dependent suppression of both phases of the primary humoral immune response in the hemolytic plaque assay, the hemagglutination titer and in the ratio of the spleen weight to final body weight. Mice treated with (+)-7-OH-delta-6-THC-DMH (0.01, 0.05, 0.01, 0.5 and 1.0 mg/kg) did not exhibit dose-dependent immune suppression. However, the (+) enantiomer reduced the number of plaque-forming cells in the hemolytic plaque assay during the inductive phase. Mice treated with a combination of (-) and (+) enantiomers, each at 0.01 mg/kg, exhibited no impairment in ability to undergo a primary humoral immune response (inductive phase).