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

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

We tested the hypothesis that an endogenous cannabinoid (CB) receptor agonist, such as N-arachidonylethanolamine (anandamide), is the transmitter that mediates perivascular sensory nerve-dependent Ca2+-induced relaxation. Rat mesenteric branch arteries were studied using wire myography; relaxation was determined after inducing contraction with norepinephrine. Cumulative addition of Ca2+ caused dose-dependent relaxation (ED50 = 2.2 +/- 0.09 mM). The relaxation was inhibited by 10 mM TEA and 100 nM iberiotoxin, a blocker of large conductance Ca2+-activated K+ channels, but not by 5 microM glibenclamide, 1 mM 4-aminopyridine, or 30 nM apamin. Ca2+-induced relaxation was also blocked by the selective CB receptor antagonist SR141716A and was enhanced by pretreatment with 4-(2-aminoethyl)benzenesulfonyl fluoride hydrochloride (pefabloc; 30 microM), an inhibitor of anandamide metabolism. Anandamide also caused dose-dependent relaxation (ED50 =.72 +/- 0.3 microM). The relaxation was not inhibited by endothelial denudation, 10 microM indomethacin, or 1 microM miconazole, but was blocked by 3 microM SR141716A, 10 mM TEA, precontraction with 100 mM K+, and 100 nM iberiotoxin, and was enhanced by treatment with 30 microM pefabloc. Mesenteric branch arteries were 200-fold more sensitive to the relaxing action of anandamide than arachidonic acid (ED50 = 160 +/- 7 microM). These data show that: 1) Ca2+ and anandamide cause hyperpolarization-mediated relaxation of mesenteric branch arteries, which is dependent on an iberiotoxin-sensitive Ca2+-activated K+ channel, 2) relaxation induced by both Ca2+ and anandamide is inhibited by CB receptor blockade, and 3) relaxation induced by anandamide is not dependent on its breakdown to arachidonic acid and subsequent metabolism. These findings support the hypothesis that anandamide, or a similar cannabinoid receptor agonist, mediates nerve-dependent Ca2+-induced relaxation in the rat.
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PMID:A role for N-arachidonylethanolamine (anandamide) as the mediator of sensory nerve-dependent Ca2+-induced relaxation. 1008 11

The influence of the cannabinoids anandamide, methanandamide and WIN 55212-2 on the delayed rectifier K(+) current (I(K(V))) in rat arterial myocytes was investigated. Anandamide caused a concentration-dependent reduction of total peak and late K(+) current (I(K)). The maximal effect (about 50% inhibition of I(K)) was reached with 3 microM, and half-maximal current block was observed at 0.6 microM. Blockade was voltage-independent. Inhibition of I(K) by the cannabinoid was associated with a characteristic increase in the rate of current relaxation. Methanandamide (10 microM), a metabolically more stable analogue of anandamide, decreased I(K) with a similar time course. Current traces in the presence of the drug also showed an acceleration of inactivation. The presence of TEA did not impair the inhibition by anandamide or methanandamide, but inhibition was prevented by pre-exposure to 4-AP, showing that both cannabinoids inhibited I(K(V)) while having no influence on Ca(2+)-dependent K(+) current (I(K(Ca))). The CB(1) receptor antagonist SR141716A (10 microM) did not influence the action of anandamide or methanandamide. Arachidonic acid (1 microM) increased I(K) considerably. However, in the presence of TEA it caused a decrease of I(K(V)) with a characteristic increase in the rate of current relaxation. WIN 55212-2 (20 microM) caused similar inhibition of I(K). Internally applied anandamide (10 microM) or methanandamide (10 microM) was ineffective at influencing I(K). In the dialyzed cells, the additional external application of a cannabinoid promptly initiated inhibition. The results show that anandamide, methanandamide and WIN 55212-2 affect I(K(V)) in a cannabinoid receptor-independent way similar to that of arachidonic acid, which, unlike the cannabinoids, additionally increases a Ca(2+)-activated K(+) current. It is suggested that cannabinoids might bind to an external site on or near the K(v) channel of the vascular smooth muscle cells.
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PMID:Influence of cannabinoids on the delayed rectifier in freshly dissociated smooth muscle cells of the rat aorta. 1096 73

1. The cannabinoid arachidonyl ethanolamide (anandamide) caused concentration-dependent relaxation of 5-HT-precontracted, myograph-mounted, segments of rat left anterior descending coronary artery. 2. This relaxation was endothelium-independent, unaffected by the fatty acid amide hydrolase inhibitor, arachidonyl trifluoromethyl ketone (10 microM), and mimicked by the non-hydrolysable anandamide derivative, methanandamide. 3. Relaxations to anandamide were attenuated by the cannabinoid receptor antagonist, SR 141716A (3 microM), but unaffected by AM 251 (1 microM) and AM 630 (1 microM), more selective antagonists of cannabinoid CB(1) and CB(2) receptors respectively. Palmitoylethanolamide, a selective CB(2) receptor agonist, did not relax precontracted coronary arteries. 4. Anandamide relaxations were not affected by inhibition of sensory nerve transmission with capsaicin (10 microM) or blockade of vanilloid VR1 receptors with capsazepine (5 microM). Nevertheless capsaicin relaxed coronary arteries in a concentration-dependent and capsazepine-sensitive manner, confirming functional sensory nerves were present. In contrast, capsazepine and capsaicin did inhibit anandamide relaxations in methoxamine-precontracted rat small mesenteric arteries. 5. Relaxations to anandamide were inhibited by TEA (1 mM) or iberiotoxin (50 nM), blockers of large conductance, Ca(2+)-activated K(+) channels (BK(Ca)). Gap junction inhibition with 18alpha-glycyrrhetinic acid (100 microM) did not affect anandamide relaxations. 6. This study shows anandamide relaxes the rat coronary artery by a novel mechanism. Anandamide-induced relaxations do not involve the endothelium, degradation into active metabolites, or activation of cannabinoid CB(1) or CB(2) receptors, but may involve activation of BK(Ca). Vanilloid receptor activation also has no role in the effects of anandamide in coronary arteries, even though functional sensory nerves are present.
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PMID:Mechanisms of anandamide-induced vasorelaxation in rat isolated coronary arteries. 1160 34

1. The effects of the endocannabinoid, anandamide, and its metabolically stable analogue, methanandamide, on induced tone were examined in sheep coronary artery rings in vitro. 2. In endothelium-intact rings precontracted to the thromboxane A(2) mimetic, U46619, anandamide (0.01 - 30 microM) induced slowly developing concentration-dependent relaxations (pEC(50) [negative log of EC(50)]=6.1+/-0.1; R(max) [maximum response]=81+/-4%). Endothelium denudation caused a 10 fold rightward shift of the anandamide concentration-relaxation curve without modifying R(max). Methanandamide was without effect on U46619-induced tone. 3. The anandamide-induced relaxation was unaffected by the cannabinoid receptor antagonist, SR 141716A (3 microM), the vanilloid receptor antagonist, capsazepine (3 and 10 microM) or the nitric oxide synthase inhibitor, L-NAME (100 microM). 4. The cyclo-oxygenase inhibitor, indomethacin (3 and 10 microM) and the anandamide amidohydrolase inhibitor, PMSF (70 and 200 microM), markedly attenuated the anandamide response. The anandamide transport inhibitor, AM 404 (10 and 30 microM), shifted the anandamide concentration-response curve to the right. 5. Precontraction of endothelium-intact rings with 25 mM KCl attenuated the anandamide-induced relaxations (R(max)=7+/-7%), as did K(+) channel blockade with tetraethylammonium (TEA; 3 microM) or iberiotoxin (100 nM). Blockade of small conductance, Ca(2+)-activated K(+) channels, delayed rectifier K(+) channels, K(ATP) channels or inward rectifier K(+) channels was without effect. 6. These data suggest that the relaxant effects of anandamide in sheep coronary arteries are mediated in part via the endothelium and result from the cellular uptake and conversion of anandamide to a vasodilatory prostanoid. This, in turn, causes vasorelaxation, in part, by opening potassium channels.
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PMID:Anandamide-induced relaxation of sheep coronary arteries: the role of the vascular endothelium, arachidonic acid metabolites and potassium channels. 1168 48

In the present study, the relaxant effect of the cannabinoid methanandamide was explored in rat gastric arteries. Since in some vessels cannabinoids have been shown to release calcitonin gene-related peptide (CGRP) from perivascular nerves, the influence of methanandamide was compared with that of exogenous CGRP. Methanandamide and CGRP elicited concentration-dependent, endothelium-independent relaxations. Methanandamide-induced relaxations were unaffected by the CB1 receptor antagonist AM251, the CB2 receptor antagonists AM630 and SR144528, and combined pre-exposure to AM251 and SR144528. Pre-exposure to O-1918, an antagonist of a novel nonCB1/nonCB2 cannabinoid receptor, did not influence the relaxations to methanandamide. Capsaicin or capsazepine treatment slightly inhibited methanandamide-induced relaxations. Preincubation with 30 mmol/L extracellular K+ or 3 mmol/L TEA had no significant effect on the responses elicited by methanandamide, but reduced CGRP-induced relaxations. Relaxation to 10(-5) mol/L methanandamide was significantly blunted by Bay K8644 and by preincubation with nifedipine. Furthermore, 10(-5) mol/L methanandamide significantly inhibited CaCl2-induced contractions in norepinephrine-stimulated vessels previously depleted of intra- and extracellular Ca2+. Finally, preincubation with 10(-5) mol/L methanandamide almost completely abolished high K+-induced contractions. These findings suggest that the vasorelaxant action of methanandamide in rat gastric arteries is not mediated by stimulation of known cannabinoid receptors and only partly related to stimulation of TRPV1 receptors on perivascular nerves. At high concentrations, methanandamide might induce relaxation by reducing calcium entry into the smooth muscle cells.
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PMID:Characterization of the vasorelaxation to methanandamide in rat gastric arteries. 1721 76