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Query: UNIPROT:P21554 (cannabinoid receptor)
 3,582 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We examined the question of whether cannabinoid receptors modulating noradrenaline release are detectable in the brain of humans and experimental animals. For this purpose, hippocampal slices from humans, guinea-pigs, rats and mice and cerebellar, cerebrocortical and hypothalamic slices from guinea-pigs were incubated with [3H]noradrenaline and then superfused. Tritium overflow was evoked either electrically (0.3 or 1 Hz) or by introduction of Ca2+ ions (1.3 mM) [corrected] into Ca(2+)-free, K(+)-rich medium (25 mM) [corrected] containing tetrodotoxin 1 microM. Furthermore, the cAMP accumulation stimulated by forskolin 10 microM was determined in guinea-pig hippocampal membranes. We used the following drugs: the cannabinoid receptor agonists (-)-cis-3-[2-hydroxy-4-(1,1- dimethylheptyl)phenyl]-trans-4-(3-hydroxypropyl)cyclo-hexanol (CP-55,940) and R(+)-[2,3-dihydro-5-methyl-3- [(morpholinyl)methyl]pyrrolo[1,2,3-de]-1,4-benzoxazinyl]- (1-naphthalenyl)methanone (WIN 55,212-2), the inactive S(-)-enantiomer of the latter (WIN 55,212-3) and the CB1 receptor antagonist N-piperidino-5-(4-chlorophenyl)- 1-(2,4-dichlorophenyl)-4-methyl-3-pyrazole-carboxamide (SR 141716). The electrically evoked tritium overflow from guinea-pig hippocampal slices was reduced by WIN 55,212-2 (pIC30% 6.5) but not affected by WIN 55,212-3 up to 10 microM. The concentration-response curve of WIN 55,212-2 was shifted to the right by SR 141716 (0.032-microM) (apparent pA2 8.2), which by itself did not affect the evoked overflow. WIN 55,212-2 1 microM also inhibited the Ca(2+)-evoked tritium overflow in guinea-pig hippocampal slices and the electrically evoked overflow in guinea-pig cerebellar, cerebrocortical and hypothalamic slices as well as in human hippocampal slices but not in rat and mouse hippocampal slices. SR 141716 (0.32 microM) markedly attenuated the WIN 55,212-2-induced inhibition in guinea-pig and human brain slices. SR 141716 0.32 microM by itself increased the electrically evoked tritium overflow in guinea-pig hippocampal slices but failed to do so in slices from the other brain regions of the guinea-pig and in human hippocampal slices but failed to do so in slices from the other brain regions of the guinea-pig and in human hippocampal slices. The cAMP accumulation stimulated by forskolin was reduced by CP-55,940 and WIN 55,212-2. The concentration-response curve of CP 55,940 was shifted to the right by SR 141716 (0.1 microM; apparent pA2 8.3), which by itself did not affect cAMP accumulation. In conclusion, cannabinoid receptors of the CB1 subtype occur in the human hippocampus, where they may contribute to the psychotropic effects of cannabis, and in the guinea-pig hippocampus, cerebellum, cerebral cortex and hypothalamus. The CB1 receptor in the guinea-pig hippocampus is located presynaptically, is activated by endogenous cannabinoids and may be negatively coupled to adenylyl cyclase.
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PMID:Cannabinoid CB1 receptor-mediated inhibition of noradrenaline release in the human and guinea-pig hippocampus. 940 37

1. Relaxation of the methoxamine-precontracted rat small mesenteric artery by endothelium-derived hyperpolarizing factor (EDHF) was compared with relaxation to the cannabinoid, anandamide (arachidonylethanolamide). EDHF was produced in a concentration- and endothelium-dependent fashion in the presence of NG-nitro-L-arginine methyl ester (L-NAME, 100 microM) by either carbachol (pEC50 [negative logarithm of the EC50] = 6.19 +/- 0.01, Rmax [maximum response] = 93.2 +/- 0.4%; n = 14) or calcium ionophore A23187 (pEC50 = 6.46 +/- 0.02, Rmax = 83.6 +/- 3.6%; n = 8). Anandamide responses were independent of the presence of endothelium or L-NAME (control with endothelium: pEC50 = 6.31 +/- 0.06, Rmax = 94.7 +/- 4.6%; n = 10; with L-NAME: pEC50 = 6.33 +/- 0.04, Rmax = 93.4 +/- 6.0%; n = 4). 2. The selective cannabinoid receptor antagonist, SR 141716A (1 microM) caused rightward shifts of the concentration-response curves to both carbachol (2.5 fold) and A23187 (3.3 fold). It also antagonized anandamide relaxations in the presence or absence of endothelium giving a 2 fold shift in each case. SR 141716A (10 microM) greatly reduced the Rmax values for EDHF-mediated relaxations to carbachol (control, 93.2 +/- 0.4%; SR 141716A, 10.7 +/- 2.5%; n = 5; P < 0.001) and A23187 (control, 84.8 +/- 2.1%; SR 141716A, 3.5 +/- 2.3%; n = 6; P < 0.001) but caused a 10 fold parallel shift in the concentration-relaxation curve for anandamide without affecting Rmax. 3. Precontraction with 60 mM KCl significantly reduced (P < 0.01; n = 4 for all) relaxations to 1 microM carbachol (control 68.8 +/- 5.6% versus 17.8 +/- 7.1%), A23187 (control 71.4 +/- 6.1% versus 3.9 +/- 0.45%) and anandamide (control 71.1 +/- 7.0% versus 5.2 +/- 3.6%). Similar effects were seen in the presence of 25 mM K+. Incubation of vessels with pertussis toxin (PTX; 400 ng ml-1, 2 h) also reduced (P < 0.01; n = 4 for all) relaxations to 1 microM carbachol (control 63.5 +/- 7.5% versus 9.0 +/- 3.2%), A23187 (control 77.0 +/- 5.8% versus 16.2 +/- 7.1%) and anandamide (control 89.8 +/- 2.2% versus 17.6 +/- 8.7%). 4. Incubation of vessels with the protease inhibitor phenylmethylsulphonyl fluoride (PMSF; 200 microM) significantly potentiated (P < 0.01), to a similar extent (approximately 2 fold), relaxation to A23187 (pEC50: control, 6.45 +/- 0.04; PMSF, 6.74 +/- 0.10; n = 4) and anandamide (pEC50: control, 6.31 +/- 0.02; PMSF, 6.61 +/- 0.08; n = 8). PMSF also potentiated carbachol responses both in the presence (pEC50: control, 6.25 +/- 0.01; PMSF, 7.00 +/- 0.01; n = 4; P < 0.01) and absence (pEC50: control, 6.41 +/- 0.04; PMSF, 6.88 +/- 0.04; n = 4; P < 0.001) of L-NAME. Responses to the nitric oxide donor S-nitroso-N-acetylpenicillamine (SNAP) were also potentiated by PMSF (pEC50: control, 7.51 +/- 0.06; PMSF, 8.00 +/- 0.05, n = 4, P < 0.001). 5. EDHF-mediated relaxation to carbachol was significantly attenuated by the K+ channel blocker tetraethylammonium (TEA; 1 mM) (pEC50: control, 6.19 +/- 0.01; TEA, 5.61 +/- 0.01; n = 6; P < 0.01). In contrast, TEA (1 mM) had no effect on EDHF-mediated relaxation to A23187 (pEC50: control, 6.47 +/- 0.04; TEA, 6.41 +/- 0.02, n = 4) or on anandamide (pEC50: control, 6.28 +/- 0.06; TEA, 6.09 +/- 0.02; n = 5). TEA (10 mM) significantly (P < 0.01) reduced the Rmax for anandamide (control, 94.3 +/- 4.0%; 10 mM TEA, 60.7 +/- 4.4%; n = 5) but had no effect on the Rmax to carbachol or A23187. 6. BaCl2 (100 microM), considered to be selective for blockade of inward rectifier K+ channels, had no significant effect on relaxations to carbachol or A23187, but caused a small shift in the anandamide concentration-response curve (pEC50: control, 6.39 +/- 0.01; Ba2+, 6.20 +/- 0.01; n = 4; P < 0.01). BaCl2 (1 mM; which causes non-selective block of K+ channels) significantly (P < 0.01) attenuated relaxations to all three agents (pEC50 values: carbachol, 5.65 +/- 0.02; A23187, 5.84 +/- 0.04; anandamide, 5.95 +/- 0.02; n = 4 for each). 7. Apamin (1mu M), a selective blocker of small conductance, Ca2+-activated, K+ channels (SKCa), 4-aminopyridine (1mM), a blocker of delayed rectifier, voltage-dependent, K+ channels (Kv), and ciclazindol (10mu M), an inhibitor of Kv and adenosine 5'-triphosphate (ATP)-sensitive K+ channels (KATP), significantly reduced EDHF-mediated relaxations to carbachol, but had no significant effects on A23187 or anandamide responses. 8. Glibenclamide (10mu M), a KATP inhibitor and charybdotoxin (100 or 300nM), a blocker of several K+ channel subtypes, had no significant effect on relaxations to any of the agents. Iberiotoxin (50nM), an inhibitor of large conductance, Ca2+-activated, K+ channels (BKCa), had no significant effect on the relaxation responses, either alone or in combination with apamin (1muM). Also, a combination of apamin (1muM) with either glibenclamide (10muM) or 4-aminopyridine (1mM) did not inhibit relaxation to carbachol significantly more than apamin alone. Neither combination had any significant effect on relaxation to A23187 or anandamide. 9. A combination of apamin (1muM) with charybdotoxin (100nM) abolished EDHF-mediated relaxation to carbachol, but had no significant effect on that to A23187. Apamin (1muM) and charybdotoxin (300nM) together consistently inhibited the response to A23187, while apamin (1muM) and ciclazindol (10muM) together inhibited relaxations to both carbachol and A23187. None of these toxin combinations had any significant effect on relaxation to anandamide. 10. It was concluded that the differential sensitivity to K+ channel blockers of EDHF-mediated responses to carbachol and A23187 might be due to actions on endothelial generation of EDHF, as well as its actions on the vascular smooth muscle, and suggests care must be taken in choosing the means of generating EDHF when making comparative studies. Also, the relaxations to EDHF and anandamide may involve activation of cannabinoid receptors, coupled via PTX-sensitive G-proteins to activation of K+ conductances. The results support the hypothesis that EDHF is an endocannabinoid but relaxations to EDHF and anandamide show differential sensitivity to K+ channel blockers, therefore it is likely that anandamide is not identical to EDHF in the small rat mesenteric artery.
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PMID:A comparison of EDHF-mediated and anandamide-induced relaxations in the rat isolated mesenteric artery. 942 1

1. The effects of anandamide on K+ currents and membrane potential have been examined in freshly-isolated smooth muscle cells from rat hepatic artery and the results compared with the effects of this arachidonic acid derivative on tension and membrane potential changes in segments of whole artery. 2. In the presence of 0.3 mM L-NOARG and 10 microM indomethacin, anandamide (0.1-100 microM) and endothelium-derived hyperpolarizing factor (EDHF; liberated by acetylcholine, 0.01-10 microM) each relaxed endothelium-intact segments of hepatic artery precontracted with phenylephrine. These effects of anandamide, but not those of EDHF, were antagonized by the cannabinoid receptor antagonist, SR141716A (3 microM). 3. The relaxant effects of anandamide were unaffected by a toxin combination (apamin plus charybdotoxin, each 0.3 microM) which abolishes EDHF relaxations and were essentially unchanged in endothelium-denuded arteries. The relaxant effects of anandamide in endothelium-intact arteries were significantly reduced in a physiological salt solution containing 30 mM KCl and abolished when the K+ concentration was raised to 60 mM. 4. Anandamide (10 microM), acetylcholine (1 microM, via release of EDHF) and levcromakalim (10 microM) each markedly hyperpolarized the membrane potential of the smooth muscle cells of endothelium-intact arteries. However, when the endothelium was removed, the hyperpolarizing effects of both anandamide (10 microM) and acetylcholine were essentially abolished whereas those of levcromakalim (10 microM) were unaffected. 5. Under voltage-clamp conditions, anandamide (10 microM) abolished spontaneous transient outward currents (STOCs) in freshly-isolated single hepatic artery cells held at 0 mV but had no effect on the holding current at this potential. In current-clamp mode, the spontaneous hyperpolarizing potentials which corresponded to the STOCs were abolished with no significant change in basal membrane potential. 6. Anandamide (10 microM) abolished the iberiotoxin-sensitive K+ current (IBK(Ca)) produced by caffeine and the corresponding hyperpolarizations generated by this xanthine derivative in current-clamp mode. In contrast, anandamide had no effect on IBK(Ca) generated on exposure to NS1619 (30 microM). 7. It was concluded that anandamide is not EDHF in the rat hepatic artery. Anandamide-induced hyperpolarization is exerted indirectly and requires the presence of the endothelium. Anandamide also acts on the smooth muscle cells to inhibit processes which require functional intracellular calcium stores. This direct action seems more important than membrane hyperpolarization in relaxing phenylephrine-contracted vessels.
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PMID:Studies on the effects of anandamide in rat hepatic artery. 942 14

Anandamide is an endogenous ligand of cannabinoid receptors that induces pharmacological responses in animals similar to those of cannabinoids such as delta9-tetrahydrocannabinol (THC). Typical pharmacological effects of cannabinoids include disruption of pain, memory formation, and motor coordination, systems that all depend on NMDA receptor mediated neurotransmission. We investigated whether anandamide can influence NMDA receptor activity by examining NMDA-induced calcium flux (deltaCa2+NMDA) in rat brain slices. The presence of anandamide reduced deltaCa2+NMDA and the inhibition was disrupted by cannabinoid receptor antagonist, pertussis toxin treatment, and agatoxin (a calcium channel inhibitor). Whereas these treatments prevented anandamide inhibiting deltaCa2+NMDA, they also revealed another, underlying mechanism by which anandamide influences deltaCa2+NMDA. In the presence of cannabinoid receptor antagonist, anandamide potentiated deltaCa2+NMDA in cortical, cerebellar, and hippocampal slices. Anandamide (but not THC) also augmented NMDA-stimulated currents in Xenopus oocytes expressing cloned NMDA receptors, suggesting a capacity to directly modulate NMDA receptor activity. In a similar manner, anandamide enhanced neurotransmission across NMDA receptor-dependent synapses in hippocampus in a manner that was not mimicked by THC and was unaffected by cannabinoid receptor antagonist. These data demonstrate that anandamide can modulate NMDA receptor activity in addition to its role as a cannabinoid receptor ligand.
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PMID:Dual effects of anandamide on NMDA receptor-mediated responses and neurotransmission. 945 61

A three-dimensional model of human cannabinoid receptor is constructed using computer-aided molecular modeling techniques. The helices of bacteriorhodopsin were used as the initial template to construct the transmembrane helices. The extracellular and intracellular loops were added using the SYBYL molecular modeling package. The extracellular N terminus was modeled on the basis of its similarity to rat oncomodulin. Similarly, the C terminus was constructed on the basis of similarity to bovine prothrombin fragment 1. The final structure was refined by several runs of minimization and dynamics calculation using the CHARMm package. delta 9-Tetra hydrocannabinol was docked into the internal cavity using the AUTODOCK program. Our study snows that there may be a calcium-binding site in the extracellular N terminus of this receptor. The ligand binds mainly to a hydrophobic site, which consists of residues Met-240, Trp-241 (TMH-4), Trp-356, Leu-359, Leu-360 (TMH-6), and Ala-283 (TMH-5). Its phenolic hydroxyl group forms a hydrogen bond with the carboxy group of Ala-198 (TMH-3). The results of modeling agree well with experimental QSAR studies.
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PMID:The cannabinoid receptor: computer-aided molecular modeling and docking of ligand. 945 16

This review presents and explores the hypothesis that N-arachidonylethanolamine (AEA, also called anandamide) is synthesized in the brain and functions as an endogenous ligand of the cannabinoid receptor. Support for this hypothesis comes from in vitro experiments demonstrating that AEA binds and activates signaling through the cannabinoid receptor. In addition, in vivo AEA produces effects very similar to those of the classical agonists of the cannabinoid receptor. Evidence for the cellular synthesis and release of AEA is not as clear. Data are presented that suggest that AEA is synthesized via a two enzyme process. First, a novel phospholipid (N-arachidonylphosphatidylethanolamine) is formed by a calcium-dependent transacylase. This lipid is a substrate for a phosphodiesterase of the phospholipase D type which releases AEA. Although there is some evidence to support this hypothesis, it is clear that AEA is a very minor product of this enzymatic cascade. Several important questions remain to be answered, including whether the concentrations of AEA synthesized by cells are sufficient to support a signaling role in the brain.
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PMID:Biochemistry and pharmacology of arachidonylethanolamide, a putative endogenous cannabinoid. 945 63

The effects of the cannabinoid receptor agonist Win55,212 on Ca2+ channels were studied in rat hippocampal neurons grown in primary culture. Win55,212-2 inhibited whole-cell Ba2+ currents through Ca2+ channels by both CB1 receptor-mediated and direct mechanisms. The concentration dependent inhibition of the current showed two clear phases, a high-affinity receptor-mediated phase (IC50=14+/-2 nM) that was stereoselective and sensitive to a CB1 receptor antagonist, 300 nM SR141716, and a non-saturating phase that was neither stereoselective nor inhibited by SR141716. These concentration-dependent effects were paralleled by Win55212-induced inhibition of glutamatergic synaptic transmission. Win55,212-2 (100 nM) inhibited both omega-agatoxin IVA- and omega-conotoxin GVIA-sensitive currents. Thus, activation of cannabinoid receptors inhibits N- and P/Q-type Ca2+ channels. Activation of cannabinoid receptors inhibited only a fraction of the whole-cell Ca2+ channel current (17+/-2%) even though more than half of the whole-cell Ba2+ current was carried by N- and P/Q-type Ca2+ channels. Concentrations of agonist greater than 1 microM inhibited Ca2+ channels directly.
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PMID:The cannabinoid agonist Win55,212-2 inhibits calcium channels by receptor-mediated and direct pathways in cultured rat hippocampal neurons. 947 52

We have found that phosphorylation of a G-protein-coupled receptor by protein kinase C (PKC) disrupts modulation of ion channels by the receptor. In AtT-20 cells transfected with rat cannabinoid receptor (CB1), the activation of an inwardly rectifying potassium current (Kir current) and depression of P/Q-type calcium channels by cannabinoids were prevented by stimulation of protein kinase C by 100 nM phorbol 12-myristate 13-acetate (PMA). In contrast, activation of Kir current by somatostatin was unaffected, and inhibition of calcium channels was only modestly attenuated. The possibility that PKC acted by phosphorylating CB1 receptors was confirmed by demonstrating that PKC phosphorylated a single serine (S317) of a fusion protein incorporating the third intracellular loop of CB1. Mutating this serine to alanine did not affect the ability of CB1 to modulate currents, but it eliminated disruption by PMA, demonstrating that PKC can disrupt ion channel modulation by receptor phosphorylation.
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PMID:Protein kinase C disrupts cannabinoid actions by phosphorylation of the CB1 cannabinoid receptor. 952

Whole-cell patch-clamp recordings were made from substantia nigra pars reticulata (SNR) neurones in rat midbrain slices to investigate the electrophysiological effects of cannabinoids. The cannabinoid receptor agonist WIN 55212-2 (10 microM) significantly reduced intranigrally evoked and spontaneous inhibitory post-synaptic currents (IPSCs) which were mediated by GABA(A) receptors. The postsynaptic current induced by bath application of GABA was not affected by the presence of WIN 55212-2. The actions of WIN 55212-2 were not mimicked by the inactive enantiomer WIN 55212-3. WIN 55212-2 also hyperpolarized the membrane of SNR neurones in a tetrodotoxin/0-Ca2+-insensitive manner. These data suggest that cannabinoids modulate the activity of SNR neurones by presynaptic inhibition of GABA inputs. They may also exert a direct post-synaptic inhibition on these neurones.
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PMID:Presynaptic inhibition of GABAergic inputs to rat substantia nigra pars reticulata neurones by a cannabinoid agonist. 955 36

Electrophysiological consequences of activation of cannabinoid receptors have been mostly investigated on neuronal cell lines and on cells transfected with cannabinoid receptors. The aim of the present experiments was to study cannabinoid effects on identified neurons in situ. Electrically-evoked postsynaptic currents and voltage-dependent calcium currents were investigated in the principal neurons of the corpus striatum, the medium spiny neurons, with the patch-clamp method for brain slices. These neurons were chosen because they produce messenger RNA for cannabinoid receptors and because the density of cannabinoid binding sites in the striatum is high. Activation of muscarinic receptors by carbachol (10(-5) M) reduced inhibitory postsynaptic current amplitude by 67%. The synthetic cannabinoid receptor agonist R(+)-[2,3-dihydro-5-methyl-3-[(morpholinyl)methyl]pyrrolo[1,2,3-de]-1,4- benzoxazin-yl]-(1-naphtalenyl)methanone (WIN55212-2; 10(-8) to 10(-5) M) dose-dependently reduced striatal inhibitory postsynaptic currents; the maximum effect, inhibition by 52%, was observed at 10(-6) M. Another cannabinoid agonist, (-)-cis-3-[2-hydroxy-4-(1,1-dimethylheptyl)phenyl]-trans-4-(3-hydr oxypropyl)cyclohexanol (CP55940; 10(-6) M), also reduced inhibitory postsynaptic currents, by 50%. The CB1 cannnabinoid receptor antagonist N-piperidino-5-(4-chlorophenyl)-1-(2,4-dichlorophenyl)4-methyl-3-pyra zolecarboxamide (SR141716A; 10(-6) M) had no effect when given alone but abolished the effect of WIN55212-2 (10(-6) M). WIN55212-2 (10(-6) M) did not change the current evoked by the GABA(A)-receptor agonist muscimol (10(-6) M). Activation of muscarinic receptors by carbachol (10(-5) M) inhibited voltage-dependent calcium currents by 21%, but the cannabinoid receptor agonist WIN55212-2 (10(-6) M) was without effect. The results show that activation of CB1 cannabinoid receptors reduces GABAergic inhibitory postsynaptic currents in medium spiny neurons of the corpus striatum: the likely mechanism is presynaptic inhibition of GABA release from terminals of recurrent axons of the medium spiny neurons themselves.
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PMID:Inhibition of GABAergic inhibitory postsynaptic currents by cannabinoids in rat corpus striatum. 962 39


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