Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0043167 (pertussis)
 19,595 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In C6 glioma cells stably expressing a homogeneous population of the cloned rat mu opioid receptor, the binding affinities of opioid agonists and subsequent activation of G protein were examined. Opioid receptor number in membranes of these cells was high (10-30 pmol/mg protein [3H]diprenorphine binding sites). Opioids were found to bind to the receptor with high affinity [Tyr-D-Ala-Gly-(Me)Phe-Gly-ol (DAMGO) 0.23 nM; sufentanil 0.034 nM; morphine 0.16 nM]. Activation of G protein by opioid agonists was examined by measuring the stimulation of guanosine-5'-O-(3-[35S]thio)triphosphate ([35S]GTP gamma S) binding. Sufentanil increased [35S]GTP gamma S binding by 326% with an EC50 value of 2.39 nM. Agonist stimulation of [35S]GTP gamma S binding was stereoselective, naltrexone-reversible, and pertussis toxin-sensitive. The "intrinsic activity" of opioids at the mu receptor was reflected by the magnitude of agonist-mediated activation of G protein. The rank order of the stimulation of [35S]GTP gamma S binding was etonitazene = sufentanil = DAMGO = PLO17 = fentanyl > morphine > profadol > meperidine > butorphanol = nalbuphine = pentazocine > cyclazocine = nalorphine > levallorphan > naltrexone. High affinity binding of ligands to the mu opioid receptor was reduced by the addition of sodium and guanosine diphosphate at concentrations used in the [35S]GTP gamma S binding assay. Ligand affinity was reduced in a manner correlating with "intrinsic activity". DAMGO, 1229-fold, nalbuphine 35-fold, naltrexone, 3-fold. The results presented show that the stable expression of the rat mu opioid receptor in C6 cells provides an effective tool to examine opioid receptor signal transduction mechanisms and evaluate the activity of novel opioids at the mu receptor.
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PMID:Characterization of opioid agonist efficacy in a C6 glioma cell line expressing the mu opioid receptor. 881 94

1. High-threshold Ca2+ channel currents were measured every 15 s following a 200 ms voltage step from -80 mV to 0 mV in order to study the coupling mechanism between neurotransmitter receptors and Ca2+ channels in neurones acutely isolated from the nucleus tractus solitarius (NTS) of the rat. 2. Application of 30 microM baclofen (GABAB receptor agonist) caused 38.9 +/- 1.2% inhibition of the peak inward Ba2+ current (IBa2+) in most NTS cells tested (n = 85 of 88). Somatostatin, 300 nM, also reduced IBa2+ by 31.3 +/- 1.6% in 53 cells of 82 tested. 3. Activation of mu-opioid-, GABAB- or somatostatin-receptors inhibited both N- and P/Q-type Ca2+ channels. 4. The inhibition of Ca2+ currents by DAMGo (mu-opioid receptor agonist), baclofen and somatostatin was reduced by treatment with pertussis toxin and partially relieved by application of a 50 ms conditioning prepulse to +80 mV. This suggests that a pertussis toxin-sensitive G-protein was involved in the neurotransmitter-mediated action in the observed inhibition of Ca2+ currents. 5. Intracellular loading with an antiserum raised against the amino terminus of Go alpha (GC/2) markedly attenuated the somatostatin-induced inhibition, but did not block the DAMGO- and baclofen-induced inhibition. 6. These findings suggest at least two different pertussis toxin-sensitive G-protein-mediated pathways are involved in receptor-induced inhibition of Ca2+ currents in the NTS.
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PMID:Mechanism of inhibition of calcium channels in rat nucleus tractus solitarius by neurotransmitters. 883 55

The experiments were designed to determine the role of pertussis toxin-(PTX) sensitive G-proteins Gi/Go in the brain and spinal cord in antinociception induced by epsilon-opioid receptor agonist beta-endorphin (beta-EP) and mu-opioid receptor agonist morphine. The effects of intracerebroventricular (i.c.v.) or intrathecal (i.t.) pretreatment with PTX on antinociception induced by morphine, beta-endorphin (beta-EP) and other selective opioid receptor agonists given i.c.v. or i.t. were studied in male ICR mice. Antinociception was assessed by the tail-flick and hot-plate tests. An i.c.v. pretreatment with PTX (0.5 microgram) caused a time- and dose-dependent attenuation of the tail-flick and hot-plate inhibition induced by i.c.v.-challenged morphine-induced antinociception. However, the same pretreatment with PTX did not affect the antinociception induced by i.c.v.-administered beta-EP. The tail-flick and hot-plate inhibition induced by selective mu-, delta- and kappa-opioid receptor agonist, DAMGO, [D-Ala2]deltorphin II and U50,488H, respectively, given i.c.v. was also attenuated by the i.c.v. pretreatment with PTX. An i.t. pretreatment with PTX (0.5 microgram) blocked markedly the tail-flick inhibition induced by morphine and beta-EP given i.c.v. However, the same treatment did not affect the hot-plate inhibition induced by beta-EP and attenuated, to a lesser degree, the hot-plate inhibition induced by morphine given i.c.v. An i.t. pretreatment with PTX blocked the tail-flick inhibition induced by selective delta 2-, alpha 2 and 5-HT receptor agonist [D-Ala2]deltorphin, norepinephrine and 5-HT, respectively, given i.t. Our results indicate that the antinociception induced by mu-, delta-, kappa-opioid receptor agonists given supraspinally is mediated by respectively opioid receptors that are coupled to PTX-sensitive Gi/Go proteins at the supraspinal sites and subsequently mediated by the activation of PTX-sensitive Gi/Go coupled receptors in the spinal cord. However, the antinociception induced by beta-EP given supraspinally is mediated by the PTX-resistant epsilon-opioid receptors at the supraspinal sites and subsequently activation of the delta 2-opioid receptors in the spinal cord that is sensitive to the pretreatment with PTX.
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PMID:Pretreatment with pertussis toxin differentially modulates morphine- and beta-endorphin-induced antinociception in the mouse. 885 73

To study cloned opioid receptor binding and modulation of both adenylyl cyclase and ion channel activity, we stably expressed mu- and delta-opioid receptors in the rodent pituitary-derived GH3 cell line. GH3 cells express G proteins and voltage-activated Ca2+ channels (predominantly of the L-type). Activation of cloned rat mu-opioid receptors expressed in GH3 cells (termed GH3MOR cells) inhibits L-type Ca2+ channel activity. GH3MOR cells, further transfected with mouse delta receptor cDNA (termed GH3MORDOR cells), bound both [D-Ala2,N-MePhe4,Gly-ol5]enkephalin (DAMGO) and [D-Pen2,D-Pen5]enkephalin (DPDPE). These opioid ligands inhibited adenylyl cyclase activity (IC50 = 174 and 0.53 nM, respectively). This action of DAMGO and DPDPE was attenuated selectively by mu- and delta-opioid receptor-specific antagonists. Activation of both opioid receptors also led to inhibition of Ca2+ channel activity, measured with Ba2+ as the charge carrier using the whole-cell patch-clamp technique. Both DAMGO (1 microM) and DPDPE (1 microM) reversibly inhibited Ba2+ currents (by 17.0 +/- 1.4% and 20.7 +/- 1.3%, respectively) in GH3MORDOR cells. The inhibitory action of DPDPE was dose dependent (IC50 = 1.6 nM) and was attenuated by pretreatment with pertussis toxin (200 ng/ml) or by the inclusion of guanosine-5'-O-(2-thio)diphosphate (2 mM) in the recording electrode. Ba2+ current inhibitions by both DAMGO and DPDPE were completely reversed by depolarizing (to > 50 mV) prepulses in GH3MORDOR cells. In summary, cloned mu- and delta-opioid receptors expressed in GH3 cells voltage-dependently couple through Gi/G(o) proteins to L-type Ca2+ channels.
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PMID:Voltage-dependent inhibition of Ca2+ channels in GH3 cells by cloned mu- and delta-opioid receptors. 886 41

Bovine chromaffin cells possess a mixture of high-voltage-activated Ca2+ channel subtypes: L-type, dihydropyridine-sensitive channels, and N-, P- and Q-types, omega-conotoxin MVIIC-sensitive channels. In these cells, we studied the reversible, naloxone-antagonized inhibition of Ba2+ currents by the opioid agonist met-enkephalin (IC50 = 272 nM). This inhibition could be resolved into a voltage-dependent and a voltage-independent component. The first was revealed by its slow Ba2+ current activation kinetics at 0 mV and by the current facilitation induced by short prepulses to +90 mV. The second was estimated as the residual inhibition persisting after the facilitation protocol. The two inhibitory components varied markedly from cell to cell and each contributed to about half of the total inhibition. Replacement of internal GTP by GDP-beta-S or cell pretreatment with pertussis toxin completely abolished the voltage-dependent inhibition by opioids, partially preserving the voltage-independent component. The opioid-induced inhibition was not selective for any Ca2+ channel subtype, being not prevented after the addition of specific Ca2+ channel antagonists. However, when separately analysing the contribution of each channel type to the voltage-dependent and voltage-independent modulation, a clear-cut distinction could be achieved. The voltage-independent inhibition was effective on all Ca2+ channel subtypes but predominantly on L-type Ca2+ channels. The voltage-dependent process was abolished by omega-conotoxin-MVIIC, but unaffected by nifedipine, and was thus sharply restricted to non-L-type channels (N-, P- and Q-types). Our data suggest a functionally distinct opioid receptor-mediated modulation of L- and non-L-type channels, i.e. of the two channel classes sharing major control of catecholamine secretion from bovine chromaffin cells.
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PMID:Opioid inhibition of Ca2+ channel subtypes in bovine chromaffin cells: selectivity of action and voltage-dependence. 892 Dec 48

Although both opioid receptors and endogenous opioids are abundant in cardiac tissues, the signal transduction pathways of opioids in cardiac sarcolemmal membranes have yet to be identified. In highly purified canine cardiac sarcolemmal membranes, binding of the opioid receptor antagonist [3H]diprenorphine and effects of mu, delta and kappa agonists on low Km GTPase and adenylyl cyclase were measured. Equilibrium binding of [3H]diprenorphine revealed a maximal binding capacity of 7.2 pmol/mg protein and a Kd of 1.3 nmol/l. In the presence of GTP, (D-Pen2,5, p-Cl-Phe4) enkephalin and (D-Arg6) dynorphin A 1-13 fragment both inhibited adenylyl cyclase by 20-25% (from 206 +/- 30 to 164 +/- 28 pmol.min-1.mg protein-1, EC50 6 mumol/L, and from 254 +/- 109 to 204 +/- 90 pmol.min-1.mg protein-1, EC50 8 mumol/L, respectively; P < 0.001). Both substances stimulated low Km GTPase by 20% and 13%, respectively (from 12.7 +/- 3.0 to 15.2 +/- 3.7 pmol.min-1.mg protein-1, EC50 12 mumol/L, P < 0.01, and from 9.1 +/- 2.8 to 10.4 +/- 3.2 pmol.min-1.mg protein-1, EC50 6 mumol/L, P < 0.05, respectively). These effects were blocked by the opioid receptor antagonist naltrexone and by pretreatment of sarcolemmal membranes with pertussis toxin. The mu opioid receptor agonists (D-Ala2, Me Phe4, Gly-[ol]5)enkephalin and morphiceptin had no effect on either adenylyl cyclase or low Km GTPase activities. These data suggest that in cardiac sarcolemma, opioid receptors are coupled to pertussis toxin sensitive G proteins and mediate inhibition of adenylyl cyclase activity.
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PMID:Opioid receptor agonists activate pertussis toxin-sensitive G proteins and inhibit adenylyl cyclase in canine cardiac sarcolemma. 893 64

Rat-1 fibroblasts were transfected with a cDNA encoding the mouse delta opioid receptor. Two separate clones, D2 (which expressed some 6 pmol of the receptor/mg of membrane protein) and DOE (which expressed some 0.2 pmol/mg of membrane protein), were examined in detail. With membranes from both clones, the opioid agonist [D-Ala2]leucine enkephalin (DADLE) caused stimulation of high-affinity GTPase activity and of the binding of guanosine 5'-[gamma-[35S]thio]triphosphate, and inhibition of forskolin-amplified adenylate cyclase activity. DADLE also induced phosphorylation and activation of both the p42MAPK (42 kDa isoform) and p44MAPK (44 kDa isoform) members of the mitogen-activated protein kinase (MAP kinase) family. All of these effects of DADLE were prevented in both clones by pretreatment of the cells with pertussis toxin. The maximal response that could be produced by DADLE in direct assays of G-protein activation were substantially greater in clone D2 than in clone DOE, but in both clones essentially full phosphorylation of both p42MAPK and p44MAPK could be achieved. EC50 values for DADLE stimulation of GTPase activity and for activation of p44MAPK were substantially lower in clone D2 than in clone DOE. Moreover, in both clones the EC50 value for DADLE stimulation of p44MAPK was substantially lower than that for stimulation of GTPase activity, and the Hill coefficients for agonist activation of p44MAPK (h > 1) displayed marked co-operativity whereas those for G-protein activation did not (h 0.8-1.0). DADLE activation of p44MAPK showed more sustained kinetics in clone D2 than in clone DOE. By contrast, lysophosphatidic acid, acting at an endogenously expressed G-protein-coupled receptor, also activated p44MAPK in both clones in a pertussis toxinsensitive manner, but both the kinetics and the concentration-response curve for activation of p44MAPK by this ligand were similar. As with other systems, maintained cellular levels of a cAMP analogue prevented the effects of both G-protein-coupled receptors on activation of p44MAPK. These results demonstrate for the first time that an opioid receptor, at least when expressed in Rat-1 fibroblasts, is able to initiate activation of the MAP kinase cascade in a G1-dependent manner, and show that only a very small proportion of the cellular G1 population is required to be activated to result in full phosphorylation of the p42MAPK and p44MAPK MAP kinases.
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PMID:Agonist activation of p42 and p44 mitogen-activated protein kinases following expression of the mouse delta opioid receptor in Rat-1 fibroblasts: effects of receptor expression levels and comparisons with G-protein activation. 894 92

Previous studies have established that the delta-selective antagonist ICI-174,864 exhibits negative intrinsic activity at the delta-opioid receptors in NG108-15 membranes. To determine whether ICI-174,864 can function as a true inverse agonist in intact cells, its ability to stimulate cAMP accumulation was examined in a human embryonic kidney 293 cell line (293/DOR) expressing the cloned murine delta-opioid receptor. Forskolin-stimulated cAMP accumulation in the 293/DOR cells was dose-dependently suppressed by the delta-selective agonist [D-Pen2, D-Pen5]enkephalin, and such inhibition was abolished by pertussis toxin or the opiate antagonist naloxone. In contrast, ICI-174,864 significantly potentiated the forskolin response. The ICI-174,864-induced enhancement of the forskolin response exhibited dose-dependency and was antagonized by [D-Pen2,D-Pen5]enkephalin and blocked by pertussis toxin. Neither ICI-174,864 nor pertussis toxin elevated the basal level of cAMP accumulation in the absence of forskolin. Other opiate antagonists, such as naloxone and naltrindole, were ineffective in enhancing the forskolin-stimulated cAMP accumulation. Elevation of cAMP levels in response to the activation of Gs (through either ligand-bound receptor or point mutation on alpha(s)) was also potentiated by ICI-174,864. Our results indicate that ICI-174,864 behaves as an inverse agonist in human embryonic kidney 293 cells stably expressing the delta-opioid receptor. The inverse agonistic effect of ICI-174,864 seemed to require Gi proteins and was clearly manifested when adenylyl cyclase was activated.
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PMID:Inverse agonistic effect of ICI-174,864 on the cloned delta-opioid receptor: role of G protein and adenylyl cyclase activation. 896 89

Chronic opioid regulation of stimulatory beta-2 adrenoceptor (beta-2 AR) signaling was investigated in human mammary epidermoid carcinoma A431 cells stably expressing the cloned rat mu opioid receptor. In the cell clone used (A431/mu 13; Bmax = 302.9 +/- 46 fmol/mg membrane protein), the addition of morphine acutely attenuated basal as well as (-)-isoproterenol-stimulated cAMP accumulation. Prolonged exposure of the cells to morphine (10 microM; 2 d) resulted in homologous desensitization of MOR function as well as heterologous sensitization of adenylate cyclase (AC). Up-regulation of AC in A431/mu 13 cells is characterized by an increased capacity rather than an increased sensitivity of beta-2 AR-stimulated AC. Moreover, opioid withdrawal falls to precipitate a cAMP overshoot in this cell system. Sensitization of stimulatory AC signaling by chronic morphine develops in a time- and dose-dependent manner and is blocked by both naloxone and pertussis toxin. Investigation into the mechanism leading to up-regulation of AC revealed a 40% increase in the number of beta-2 ARs as assessed by [125I]-cyanopindolol binding experiments. No additional quantitative changes were found for stimulatory G proteins and the effector enzyme itself. Sensitization of AC appears to be mediated solely by the increase in beta-2 AR numbers, because (+/-)-1-[2,3-(dihydro-7-methyl-1H-inden-4-yl)oxy]-3- [(1-methylethyl)amino]-2-butanol hydrochloride, which acts as an "inverse agonist" at the beta-2 AR, completely reversed elevated basal AC activities, and because the ratio between functional active beta-2 ARs and stimulatory G proteins remained unchanged. In conclusion, chronic exposure of clonal A431/ mu13 cells to morphine increases the capacity of stimulatory AC signaling by up-regulating beta-2 AR number. These results demonstrate participation of stimulatory receptor systems in the cellular mechanisms underlying opioid dependence.
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PMID:Chronic morphine treatment increases stimulatory beta-2 adrenoceptor signaling in A431 cells stably expressing the mu opioid receptor. 899 36

The ultra-potent opioid analgesic, etorphine, elicits naloxone-reversible, dose-dependent inhibitory effects, i.e., shortening of the action potential duration (APD) of naive and chronic morphine-treated sensory dorsal root ganglion (DRG) neurons, even at low (pM-nM) concentrations. In contrast, morphine and most other opioid agonists elicit excitatory effects, i.e., APD prolongation, at these low opioid concentrations, require much higher (ca. 0.1-1 microM) concentrations to shorten the APD of naive neurons, and evoke only excitatory effects on chronic morphine-treated cells even at high > 1-10 microM concentrations. In addition to the potent agonist action of etorphine at mu-, delta- and kappa-inhibitory opioid receptors in vivo and on DRG neurons in culture, this opioid has also been shown to be a potent antagonist of excitatory mu-, delta- and kappa-receptor functions in naive and chronic morphine-treated DRG neurons. The present study demonstrates that the potent inhibitory APD-shortening effects of etorphine still occur in DRG neurons tested in the presence of a mixture of selective antagonists that blocks all mu-, delta- and kappa-opioid receptor-mediated functions, whereas addition of the epsilon (epsilon)-opioid-receptor antagonist, beta-endorphin(1-27) prevents these effects of etorphine. Furthermore, after markedly enhancing excitatory opioid receptor functions in DRG neurons by treatment with GM1 ganglioside or pertussis toxin, etorphine shows excitatory agonist action on non-mu-/delta-/kappa-opioid receptor functions in these sensory neurons, in contrast to its usual potent antagonist action on mu-, delta- and kappa-excitatory receptor functions in naive and even in chronic morphine-treated cells which become supersensitive to the excitatory effects of mu-, delta- and kappa-opioid agonists. This weak excitatory agonist action of etorphine on non-mu-/delta-/kappa-opioid receptor functions may account for the tolerance and dependence observed after chronic treatment with extremely high doses of etorphine in vivo.
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PMID:Etorphine elicits anomalous excitatory opioid effects on sensory neurons treated with GM1 ganglioside or pertussis toxin in contrast to its potent inhibitory effects on naive or chronic morphine-treated cells. 900 33


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