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Query: UMLS:C0030193 (pain)
 261,466 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A common obstacle in clinical management of pathological pain is the poor response to opioid analgesics. We now report that delta9-tetrahydrocannabinol (delta9-THC)-induced antinociception remained effective in rats with pathological pain. The selective central cannabinoid receptor antagonist SR141716A, but not the generic opioid receptor antagonist naloxone, blocked the delta9-THC antinociception. Moreover, there is no cross-tolerance between the antinociceptive effects of morphine and delta9-THC in pathological pain states. The results indicate that delta9-THC antinociception is both effective and independent of opioid receptors in rats with pathological pain. Thus, the cannabinoid analgesic system may be superior to opioids in alleviating intractable pathological pain syndromes.
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PMID:Two distinctive antinociceptive systems in rats with pathological pain. 1069

CB1 cannabinoid receptors are widely distributed in the central nervous system where they mediate most of the cannabinoid-induced responses. Here we have evaluated the interactions between the CB1 cannabinoid receptors and the endogenous opioid system by assaying a number of well-characterized opioid responses, e.g. antinociception and stress-mediated effects, on mutant mice in which the CB1 receptor gene was invalidated. The spontaneous responses to various nociceptive stimuli (thermal, mechanical and visceral pain) were not changed in mutant CB1 mice. Furthermore, the absence of the CB1 cannabinoid receptor did not modify the antinociceptive effects induced by different opioid agonists: morphine (preferential mu opioid agonist), D-Pen2-D-Pen5-enkephalin (DPDPE) and deltorphin II (selective delta opioid agonists), and U-50,488H (selective kappa opioid agonist) in the hot-plate and tail-immersion tests. In contrast, the stress-induced opioid mediated responses were modified in CB1 mutants. Indeed, these mutants did not exhibit antinociception following a forced swim in water at 34 degrees C and presented a decrease in the immobility induced by the previous exposure to electric footshock. However, the antinociception induced by a forced swim in water at 10 degrees C was preserved in CB1 mutants. These results indicate that CB1 receptors are not involved in the antinociceptive responses to exogenous opioids, but that a physiological interaction between the opioid and cannabinoid systems is necessary to allow the development of opioid-mediated responses to stress.
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PMID:Reduction of stress-induced analgesia but not of exogenous opioid effects in mice lacking CB1 receptors. 1071 32

The analgesic potential of cannabinoid (CB) receptor agonists is of clinical interest. Improved understanding of the mechanisms of action of cannabinoids at sites involved in the modulation of acute and sustained inflammatory nociceptive transmission, such as the spinal cord, is essential. In vivo electrophysiology was used to compare the effect of the synthetic CB agonist, HU210, on acute transcutaneous electrical-evoked responses of dorsal horn neurons of noninflamed anaesthetized rats and anaesthetized rats with a peripheral carrageenin inflammation. CB receptor G-protein coupling in lumbar spinal cord sections of noninflamed and carrageenin-inflamed rats was studied with in vitro autoradiography of guanylyl 5'-[gamma-[35S]thio]triphosphate ([35S]GTPgammaS) binding. Spinal HU210 significantly inhibited the C-fibre-mediated late (300-800 ms) postdischarge response of dorsal horn neurons of noninflamed and carrageenin-inflamed rats; the CB1 receptor antagonist SR141716A blocked the effect of HU210. HU210 had limited effects on A-fibre-evoked dorsal horn neuronal responses of both groups of rats. HU210 significantly increased [35S]GTPgammaS binding in the dorsal horn of the spinal cord of both groups of rats compared with basal [35S]GTPgammaS binding; SR141716A blocked these effects. The predominant effect of spinal HU210, via CB1 receptor activation, was on the C-fibre driven postdischarge responses, a measure of neuronal hyperexcitability following repetitive C-fibre stimulation. Sustained, but not enhanced, antinociceptive effects of HU210 following carrageenin inflammation are reported; CB receptor G-protein coupling was not altered by inflammation. These results strengthen the body of evidence suggesting CB agonists may be an important novel analgesic approach for the treatment of sustained pain states.
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PMID:Activation of spinal cannabinoid 1 receptors inhibits C-fibre driven hyperexcitable neuronal responses and increases [35S]GTPgammaS binding in the dorsal horn of the spinal cord of noninflamed and inflamed rats. 1088 47

The possible therapeutic use of marijuana s active principles, the cannabinoids, is currently being debated. It is now known that these substances exert several of their pharmacological actions by activating specific cell membrane receptors, the CB1 and CB2 cannabinoid receptor subtypes. This knowledge led to the design of synthetic cannabinoid agonists and antagonists with high therapeutic potential. The recent discovery of the endocannabinoids, i.e. endogenous metabolites capable of activating the cannabinoid receptors, and the understanding of the molecular mechanisms leading to their biosynthesis and inactivation, opened a new era in research on the pharmaceutical applications of cannabinoids. Ongoing studies on the pathological and physiological conditions regulating the tissue levels of endocannabinoids, and on the pharmacological activity of these compounds and their derivatives, may provide a lead for the development of new drugs for the treatment of nervous and immune disorders, cardiovascular diseases, pain, inflammation and cancer. These studies are reviewed in this article with special emphasis on the chemical features that determine the interaction of endocannabinoids with the proteins mediating their activity and degradation.
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PMID:Endocannabinoids: new targets for drug development. 1090 98

Cannabis has been used for centuries in the medicinal treatment of gastrointestinal disorders. Endogenous cannabinimimetic substances such as 2-arachidonylglycerol have been isolated from gut homogenates and CB1-cannabinoid binding sites have been identified in small intestine. In this study, CB1-cannabinoid receptors (CB1-R) were immunohistochemically localized within the enteric nervous system of the pig, an omnivorous species whose digestive tract is functionally similar to humans. Two anti-CB1-R antisera, raised against N-terminal epitopes in the human CB1-R, were employed to localize receptor immunoreactivity by secondary immunofluorescence. CB1-R immunoreactivity was observed in the myenteric and submucosal ganglionated plexuses of porcine ileum and colon. In the ileum, all CB1-R-immunoreactive neurons coexpressed immunoreactivity to the cholinergic marker, choline acetyltransferase (ChAT). CB1-R/ChAT-immunoreactive neurons appeared to be in close apposition to ileal Peyer's patches, submucosal blood vessels, and intestinal crypts. In the distal colon, CB1-R-immunoreactive neurons also expressed immunoreactivity to ChAT, albeit less frequently than in ileum. Immunoreactivity to vasoactive intestinal peptide or nitric oxide synthase was not colocalized in ileal or colonic CB1-R-immunoreactive neurons. These studies indicate that CB1-R are present in cholinergic neurons in the porcine enteric nervous system. The potential roles of these receptors in intestinal motility and epithelial transport, host defense and visceral pain transmission are discussed.
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PMID:Localization of CB1-cannabinoid receptor immunoreactivity in the porcine enteric nervous system. 1107 17

The plant Cannabis sativa has been used by humans for thousands of years because of its psychoactivity. The major psychoactive ingredient of cannabis is Delta(9)-tetrahydrocannabinol, which exerts effects in the brain by binding to a G-protein-coupled receptor known as the CB1 cannabinoid receptor. The discovery of this receptor indicated that endogenous cannabinoids may occur in the brain, which act as physiological ligands for CB1. Two putative endocannabinoid ligands, arachidonylethanolamide ('anandamide') and 2-arachidonylglycerol, have been identified, giving rise to the concept of a cannabinoid signalling system. Little is known about how or where these compounds are synthesized in the brain and how this relates to CB1 expression. However, detailed neuroanatomical and electrophysiological analysis of mammalian nervous systems has revealed that the CB1 receptor is targeted to the presynaptic terminals of neurons where it acts to inhibit release of 'classical' neurotransmitters. Moreover, an enzyme that inactivates endocannabinoids, fatty acid amide hydrolase, appears to be preferentially targeted to the somatodendritic compartment of neurons that are postsynaptic to CB1-expressing axon terminals. Based on these findings, we present here a model of cannabinoid signalling in which anandamide is synthesized by postsynaptic cells and acts as a retrograde messenger molecule to modulate neurotransmitter release from presynaptic terminals. Using this model as a framework, we discuss the role of cannabinoid signalling in different regions of the nervous system in relation to the characteristic physiological actions of cannabinoids in mammals, which include effects on movement, memory, pain and smooth muscle contractility. The discovery of the cannabinoid signalling system in mammals has prompted investigation of the occurrence of this pathway in non-mammalian animals. Here we review the evidence for the existence of cannabinoid receptors in non-mammalian vertebrates and invertebrates and discuss the evolution of the cannabinoid signalling system. Genes encoding orthologues of the mammalian CB1 receptor have been identified in a fish, an amphibian and a bird, indicating that CB1 receptors may occur throughout the vertebrates. Pharmacological actions of cannabinoids and specific binding sites for cannabinoids have been reported in several invertebrate species, but the molecular basis for these effects is not known. Importantly, however, the genomes of the protostomian invertebrates Drosophila melanogaster and Caenorhabditis elegans do not contain CB1 orthologues, indicating that CB1-like cannabinoid receptors may have evolved after the divergence of deuterostomes (e.g. vertebrates and echinoderms) and protostomes. Phylogenetic analysis of the relationship of vertebrate CB1 receptors with other G-protein-coupled receptors reveals that the paralogues that appear to share the most recent common evolutionary origin with CB1 are lysophospholipid receptors, melanocortin receptors and adenosine receptors. Interestingly, as with CB1, each of these receptor types does not appear to have Drosophila orthologues, indicating that this group of receptors may not occur in protostomian invertebrates. We conclude that the cannabinoid signalling system may be quite restricted in its phylogenetic distribution, probably occurring only in the deuterostomian clade of the animal kingdom and possibly only in vertebrates.
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PMID:The neurobiology and evolution of cannabinoid signalling. 1131 86

The endogenous fatty acid ethanolamide, palmitylethanolamide, alleviated, in a dose-dependent manner, pain behaviors elicited in mice by injections of formalin (5%, intraplantar), acetic acid (0.6%, 0.5 ml per animal, intraperitoneal, i.p.), kaolin (2.5 mg per animal, i.p.), and magnesium sulfate (120 mg per kg, i.p.). The antinociceptive effects of palmitylethanolamide were prevented by the cannabinoid CB2 receptor antagonist SR144528 [N-([1s]-endo-1.3.3-trimethylbicyclo[2.3.1]heptan-2-yl)-5-(4-chloro-3-methylphenyl)-1-(4-methylbenzyl)-pyrazole-3-carboxamide], not by the cannabinoid CB1 receptor antagonist SR141716A [N-(piperidin-1-yl)-5-(4-chlorophenyl)-1-(2,4-dichlorophenyl)-4-methyl-1H-pyrazole-3-carboxamide x HCl]. By contrast, palmitylethanolamide had no effect on capsaicin-evoked pain behavior or thermal nociception. The endogenous cannabinoid, anandamide (arachidonylethanolamide), alleviated nociception in all tests (formalin, acetic acid, kaolin, magnesium sulfate, capsaicin and hot plate). These effects were prevented by the cannabinoid CB1 receptor antagonist SR141716A, not the cannabinoid CB2 receptor antagonist SR141716A. Additional fatty acid ethanolamides (oleylethanolamide, myristylethanolamide, palmitoleylethanolamide, palmitelaidylethanolamide) had little or no effect on formalin-evoked pain behavior, and were not investigated in other pain models. These results support the hypothesis that endogenous palmitylethanolamide participates in the intrinsic control of pain initiation. They also suggest that the putative receptor site activated by palmitylethanolamide may provide a novel target for peripherally acting analgesic drugs.
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PMID:Antinociceptive activity of the endogenous fatty acid amide, palmitylethanolamide. 1142 41

The active principle in marijuana, Delta(9)-tetrahydrocannabinol (THC), has been shown to have wide therapeutic application for a number of important medical conditions, including pain, anxiety, glaucoma, nausea, emesis, muscle spasms, and wasting diseases. Delta(9)-THC binds to and activates two known cannabinoid receptors found in mammalian tissue, CB1 and CB2. The development of cannabinoid-based therapeutics has focused predominantly on the CB1 receptor, based on its predominant and abundant localization in the CNS. Like most of the known cannabinoid agonists, Delta(9)-THC is lipophilic and relatively nonselective for both receptor subtypes. Clinical studies show that nonselective cannabinoid agonists are relatively safe and provide therapeutic efficacy, but that they also induce psychotropic side effects. Recent studies of the biosynthesis, release, transport, and disposition of anandamide are beginning to provide an understanding of the role of lipid transmitters in the CNS. This review attempts to link current understanding of the basic biology of the endocannabinoid nervous system to novel opportunities for therapeutic intervention. This new knowledge may facilitate the development of cannabinoid receptor-targeted therapeutics with improved safety and efficacy profiles.
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PMID:The endocannabinoid nervous system: unique opportunities for therapeutic intervention. 1144 25

Cannabinoids are known to suppress responses to noxious stimulation in animals and man. Recent research has suggested a role for endogenous cannabinoids in the descending inhibition of dorsal horn cells via a supraspinal site of action. We have recently demonstrated [J. Physiol. 506(2) (1998) 459] that the nucleus reticularis gigantocellularis pars alpha (GiA) is a major source of such descending modulation, and importantly, that this system is activated in response to noxious stimulation. We have therefore investigated the role of CB1 receptor activation in mediating the antinociceptive effects of activation of GiA in models of acute and chronic pain. Microinjections (0.5 microl 60% DMSO) of either WIN 55,212-2 (5 microg, selective CB1 agonist), SR141716A (50 microg, competitive CB1 antagonist), both compounds together, or vehicle alone into GiA were performed prior to these tests in a randomised, blind manner. In control animals, WIN 55,212-2 markedly increased withdrawal latencies in the tail flick test and reduced responses to subcutaneous formalin. These effects were blocked by co-administration of SR141716A. These data suggest that activation of cannabinoid CB1 receptor subtypes in GiA leads to behavioural analgesia. In animals with partial sciatic nerve ligation, microinjection of drugs and injection of formalin were performed contralaterally to the site of ligation. Partial sciatic nerve ligation significantly reduced behavioural responses to contralaterally applied formalin. Microinjection of SR141716A to GiA reversed this inhibition of responses to formalin in animals with partial sciatic nerve ligation. These data provide evidence that endogenous CB1 receptor ligands are involved in GiA mediated antinociception, and that this system is important for the modulation of nociceptive transmission in an animal model of chronic neuropathic pain.
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PMID:CB1 receptor mediated analgesia from the Nucleus Reticularis Gigantocellularis pars alpha is activated in an animal model of neuropathic pain. 1145 32

Previous studies in our laboratory have demonstrated that cannabinoids administered intravenously attenuate the duration of nocifensive behavior and block the development of hyperalgesia produced by intraplantar injection of capsaicin. In the present study, we extended these observations and determined whether cannabinoids attenuate capsaicin-evoked pain and hyperalgesia through spinal and peripheral mechanisms, and whether the antihyperalgesia was receptor mediated. Separate groups of rats were pretreated 7 min before capsaicin with an intrathecal injection of vehicle or the cannabinoid receptor agonist WIN 55,212-2 at doses of 0.1, 1.0 or 10 microg in 10 microl. Although the intrathecal application of WIN 55,212-2 did not alter nocifensive behavior following capsaicin, it produced a dose-dependent decrease in hyperalgesia to heat and mechanical stimuli. Intrathecal pretreatment with the CB1 receptor antagonist SR141716A (10 microg) blocked the antihyperalgesia produced by WIN 55,212-2. The ability of intrathecal administration of WIN 55,212-2 to attenuate hyperalgesia was not due to motor deficits since the highest dose of WIN 55,212-2 did not alter performance on the rota-rod test. To investigate whether cannabinoids attenuated capsaicin-evoked hyperalgesia through peripheral mechanisms, separate groups of rats were pretreated with an intraplantar injection of WIN 55,212-2 at doses of 0.1, 1.0, 10 or 30 microg in 100 microl 5 min before capsaicin. Intraplantar pretreatment with WIN 55,212-2 produced a dose-dependent attenuation of hyperalgesia to heat, but did not attenuate mechanical hyperalgesia or the duration of nocifensive behavior. The inactive enantiomer WIN 55,212-3 did not alter the development of hyperalgesia. SR141716A (100 microg) co-injected with WIN 55,212-2 (30 microg) partially attenuated the effects of WIN 55,212-2 on hyperalgesia to heat. Intraplantar injection of the highest dose of WIN 55,212-2 did not interfere with the development of hyperalgesia following capsaicin injection into the contralateral paw. These data show that cannabinoids possess antihyperalgesic properties at doses that alone do not produce antinociception, and are capable of acting at both spinal and peripheral sites.
Pain 2001 Sep
PMID:Cannabinoids attenuate capsaicin-evoked hyperalgesia through spinal and peripheral mechanisms. 1151 89


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