Endocannabinoids

Endocannabinoids are defined as endogenously produced compounds that bind to and functionally activate the cannabinoid receptors [7]. Since the discovery of anandamide (A-arachidonoylethanolamine) in 1992 [8], many other endogenous compounds that activate one of the cannabinoid receptors have been identified from mammalian tissues (see Refs [1, 2, 9] for reviews). These endocannabinoids and related compounds generally belonged to the classes of A-acyl ethanolamine, 2-acyl 

Chromatographic separation and sensitive detection methods are imperative to monitor endocannabinoids from biological samples as their relative abundance is low compared to the levels of other lipid species in the tissue matrices, even following extraction and purification. Early 

Together, these studies contributed to the development of validated procedures to measure brain-tissue levels of endocannabinoids and related lipids. In light of the considerable variability among quantitative regional estimates of endocannabinoids with different sample preparation techniques and analytical methods, assessment of relative changes with intrastudy controls provided the most reliable information on their 

Starting from the thought that a lock had been discovered, there came now the question of the endogenous key . Altough A -tetrahydrocannabinol from hemp fits nicely into this lock it could be mere serendipity the more so as THC, unlike morphine, had not been detected in the human body as an endogenous compound. In 1992, Raphael Mechoulam (Fig. 5.67), at the Hebrew University in Jerusalem, discovered the first endocannabinoid, which he extracted from a pig s brain he demonstrated its affinity to the CBl-receptor by classical displacement studies. Mechoulam named it anandamide (Sanskrit, ananda bliss). In chemical terms it is arachidonoylethanolamide (Fig. 5.68). Anandamide (Kj 52 nM) has practically the same affinity as A -tetrahydro-cannabinol (Kj 41 nM) at the CBl-receptor, but in contrast to THC, the former is rapidly deactivated hydrolytically by the enzyme anandamide amidohydro-lase. 

Two more fatty acid amides of aminoethanol were later discovered in extracts of the pig brain. These bind to the CBl receptor with comparable Kj-values. [119] Further endocannabinoids were discovered in the gastro-intes-tinal tract of the dog, and in the spleen of the mouse. These are monoglyceride esters. 2-Arachidonoylglycerol could be detected in the brain at a 170 times higher concentration than anandamide. This compound has the same effect as anandamide, both, in vivo and in vitro. 

Giuseppe Astarita, Jennifer Geaga, Faizy Ahmed, and Daniele Piomelli Department of Pharmacology, University of California, Irvine, California 92967, USA 

Application of Targeted Lipidomics for the Study of Endocannabinoid Metabolism 

The endocannabinoid system is constituted of various lipid species, which include precursors and metabolites of anandamide and 2-AG (Figs. 1 and 2). Each of these lipids appears to have functionally distinct biosynthetic pathways and 

In recent years the rapid development of high-sensitivity analytical techniques such as mass spectrometry (MS) and liquid chromatography (LC) supported the investigation of the endocannabinoids as part of a complex lipid network. The identification of lipid components of the endocannabinoid system can be achieved in a single analytical step by state-of-the-art platforms such as tandem mass spectrometry (MS/MS), which provides the detailed structural information necessary for characterization of lipids and increases specificity in complex biological matrices. Furthermore, the implementation of ionization techniques such as electrospray ionization (ESI) and atmospheric pressure chemical ionization (APCI) allow the coupling of LC to MS, and permits the separation and analysis of endocannabinoids with greater speed and accuracy. 

In the following sections we illustrate the complexity of endocannabinoid metabolism, highlighting the many questions that still remain unanswered. 

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Matias I, Di Marzo V (2007) Endocannabinoids and the control of energy balance. Trends Endocrinol Metab 18 27-37... 

Endocannabinoids are endogenous mediators acting via the binding to, and activation of, cannabinoid receptors, CBX and CB2 [1]. iV-arachidonoy 1-ethanol-amine (AEA, anandamide) and 2-arachidonoyl-glycerol (2-AG) (Fig. 1) are the two most studied endocannabinoids. In the nervous system, endocannabinoids act as... 

Endocannabinoids. Figure 1 Chemical structures of the two most studied endocannabinoids, anandamide and 2-arachidonoylglycerol, of Cannabis sativa psychoactive principle, A9-tetrahydrocannabinol, and of the CB-i receptor antagonist/inverse agonist, rimonabant. 

Endocannabinoids. Table 1 Changes of endocannabinoid levels during pathological conditions and subsequent possible pharmacological interventions... 

Disorder Effects on endocannabinoid levels Potential drugs... 

Parkinson s disease (PD) 1. In a non-human primate model of PD endocannabinoid levels are elevated in the basal ganglia and may contribute to the generation of parkinsonian symptoms and/or to expression of levodopa-induced dyskinesia. The cerebrospinal fluid of untreated PD patients contains elevated levels of AEA 1. CB-) antagonists or biosynthesis inhibitors... 

Neuronal excitotoxicity AEA levels are elevated in the hippocampus of mice treated with kainic acid. 2-AG levels are elevated in rats treated with pilocarpine These are two animal models of epileptic seizures, where the endocannabinoids play an anti-convulsant and protective function Inhibitors of cellular re-uptake... 

Neuropathic pain Endocannabinoid levels are elevated in FAAH inhibitors... 

Obesity and hyperglycemia 2. 2-AG levels are elevated in mouse adipocytes and epididymal of mice with DIO. AEA and 2-AG levels are elevated in rat insulinoma p-cells, in pancreas of mice with DIO, and in obese women. Patients with obesity or hyperglycaemia caused by type 2 diabetes exhibit elevated levels of 2-AG or of both endocannabinoids in visceral fat or blood, respectively. AEA levels are elevated in the liver of DIO mice 2. CB1 antagonists... 

Based on the role of endocannabinoids and cannabinoid receptors in several pathological conditions, the pharmacological manipulation of their levels or action is being developed as a therapeutic strategy. Enhancement of endocannabinoid signalling when this plays uniquely a protective role can be effected in a safer way using (i) cannabis extracts in which the presence of non-psychotropic cannabinoids with therapeutic activity per... 

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