UMLS:C0043167 - FACTA Search

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Query: UMLS:C0043167 (pertussis)
19,595 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Muscarinic receptor-linked Ca2+ mobilization and changes in cyclic AMP were studied in SH-SY5Y and IMR 32 human neuroblastoma cell lines. Muscarinic agonists acetylcholine, carbachol, methacholine and muscarine induced an increase in cytosolic free Ca2+ in a pertussis toxin (100 ng/ml)-insensitive manner in both cell lines. The ED50 values in IMR 32 cells (8-98 microM) were one order of magnitude higher than in SH-SY5Y cells (0.3-1.6 microM). Oxotremorine and pilocarpine failed to mobilize Ca2+ in IMR 32 cells. Pirenzepine antagonized carbachol-induced Ca2+ mobilization in SH-SY5Y cells with a Ki value in the range of 150-189 nM whereas the corresponding values in IMR 32 cells were 24-28 nM. Atropine inhibited a carbachol-stimulated increase in cytosolic Ca2+ with an equal potency in both cell lines (Ki 2-3 nM). Carbachol stimulated cyclic AMP (cAMP) accumulation in SH-SY5Y cells in a pertussis toxin-insensitive manner. In IMR 32 cells carbachol inhibited prostaglandin E1-stimulated cAMP accumulation. Treatment of IMR 32 cells with pertussis toxin abolished the inhibition of stimulated cAMP accumulation. These results suggest that in SH-SY5Y cells the M3 muscarinic receptor couples to both Ca2+ mobilization and stimulation of cAMP accumulation. In IMR 32 cells the M1 receptor seems to couple to Ca2+ mobilization whereas the inhibition of stimulated cAMP accumulation is coupled to a non-M1 subtype by an inhibitory G-protein.
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PMID:Differential coupling of muscarinic receptors to Ca2+ mobilization and cyclic AMP in SH-SY5Y and IMR 32 neuroblastoma cells. 165 23

Incubation of the rat retina with acetylcholine resulted in about a 20 to 30% decrease of basal cyclic AMP accumulation. Oxotremorine, arecoline, [4-hydroxy-2-butynyl]trimethylammonium chloride, m-chlorocarbanilate and carbachol also inhibited cyclic AMP accumulation. Nicotine had no effect. The response was blocked by atropine and pirenzepine but not gallamine. Intraocular injection of pertussis toxin 72 hr before testing also blocked the response to acetylcholine. The presence of forskolin exaggerated the response to acetylcholine. Intraocular injection of the cholinotoxin AF64A resulted in apparent supersensitivity of the response to acetylcholine. Our results suggest that rat retina contains muscarinic M1 receptors that are coupled negatively to adenylate cyclase.
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PMID:Pharmacological characterization of muscarinic receptors mediating inhibition of adenylate cyclase activity in the rat retina. 245 48

1. The mechanism by which acetylcholine (ACh), by stimulation of muscarinic receptors, acts to inhibit activation of the hyperpolarization-activated 'pacemaker' current, if was investigated in isolated rabbit sino-atrial (SA) node myocytes. 2. Intracellular loading with GTP gamma S, a non-hydrolysable analogue of GTP, did not impair the ACh action on if, but made it irreversible. On the other hand, the ACh action on if disappeared after a few minutes of cell loading with GDP beta S, a GDP analogue known to bind to G-proteins and prevent their receptor-stimulated action. Furthermore, incubation of cells in a solution containing pertussis toxin (PTX) led to abolition of the if response to ACh. These results indicate that the inhibitory effect of ACh on if is mediated by G-proteins activated by muscarinic receptors. 3. Intracellular loading with phosphodiesterase (PDE) increased the rate of if current run-down, but did not abolish the inhibitory action of ACh on if. 4. Extracellular perfusion with isobutylmethylxanthine (IBMX), a PDE inhibitor, increased if activation by shifting the current activation range to more positive voltages, as inferred by a three-pulse protocol analysis; in the presence of IBMX, the inhibition of if by ACh was not abolished. 5. The ACh-induced if depression persisted also in cells loaded with cyclic GMP. In these cells, as in those loaded with PDE, the if run-down was fast. 6. Oxotremorine, a muscarinic agonist coupled to adenylate cyclase but not to phosphoinositide turnover in cardiac cells, simulated ACh in its inhibitory action on if. The above results rule against the ACh action being mediated by PDE or by phosphoinositide turnover. 7. To investigate the possible involvement of cyclic AMP as a second messenger in the ACh action on if, we loaded cells with cyclic AMP and IBMX; under these conditions the action of ACh disappeared within a few minutes of whole-cell recording. 8. In cells where the slow inward Ca2+ current (isi) was measured together with if, ACh was seen to depress both currents. 9. In cells superfused with forskolin, the if amplitude on stepping to the half-activation voltage range was enhanced as a consequence of a depolarizing shift of the activation curve; ACh was not effective on if following stimulation by forskolin, but strongly depressed in the same cell the if current stimulated to a similar degree by isoprenaline.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Muscarinic control of the hyperpolarization-activated current (if) in rabbit sino-atrial node myocytes. 247 9

The pertussis toxin-sensitive G proteins (guanine nucleotide binding proteins)-muscarinic receptor interactions in 18-day fetal to adult rat hearts were studied. The collective concentration of these G proteins was measured by pertussis toxin-dependent ADP-ribosylation and decreased from 1.5 pmol of [32P]ADP-ribose/mg of protein in the fetal heart to 0.5 pmol of [32P]ADP-ribose/mg of protein in 21-day postpartum and older animals in a nonlinear pattern. The muscarinic receptor density diminished 2-fold from 400 fmol/mg in 1-day-old neonate to 200 fmol/mg of protein in adult hearts in a linear manner. The receptor affinity for the agonist oxotremorine and the effect of guanine nucleotide on that affinity were monitored in heart preparations of the various ages. The IC50 value for oxotremorine/[3H]quinuclidinylbenzilate competition curves in the absence or presence of guanine nucleotide increased gradually with age. Modeling of the competition curves from 1-day-old neonate and adult preparations suggested the receptor has two oxotremorine affinity states in both age groups but the ability of guanine nucleotide to shift receptors from the higher affinity state increases with age. [3H] Oxotremorine binding to the higher affinity state had KD values of 95 and 170 pM in neonate and adult heart preparations. The concentration of 5'-guanylylimidodiphosphate which caused 50% displacement of [3H]oxotremorine binding was 1.3 and 0.22 microM in neonate and adult tissue. These results suggest that although the quantity of the G proteins and muscarinic receptors diminish with development, the sensitivity of the G protein:muscarinic receptor complex to guanine nucleotide increases.
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PMID:Developmental changes of the G proteins-muscarinic cholinergic receptor interactions in rat heart. 250 74

We measured endogenous noradrenaline (NA) overflow from a vascularly perfused rat stomach in vitro. The stomach was perfused with Krebs-Ringer solution containing 10 microM pargyline. Periarterial nerves, which contain postganglionic sympathetic nerves, around the left gastric artery were stimulated for 1 min with square-wave pulses of 2 msec duration, 2.5 to 5.0 Hz, supramaximal intensity (10 mA). Oxotremorine (10(-8) to 10(-6) M) concentration-dependently inhibited the periarterial nerve stimulation-evoked NA overflow under the presence of 10(-6) M phentolamine. Bilateral vagus nerve stimulation (5 Hz, 2 msec duration, 10 mA, for 1 min) reduced the evoked NA overflow. Oxotremorine (10(-7) M)-induced inhibition of NA overflow was attenuated by atropine, methoctramine (muscarinic M2 receptor antagonist), 4-diphenylacetoxy-N-methylpiperidine (M3 receptor antagonist) and pirenzepine (M1 receptor antagonist) with the following potency; atropine > methoctramine > 4-diphenylacetoxy-N-methylpiperidine >> pirenzepine. The oxotremorine-induced inhibition was attenuated by N-ethylmaleimide (3 x 10(-5) M for 50 min), but was not affected by pertussis toxin pretreatment (10 micrograms/rat, for 4 days). However, this pretreatment with pertussis toxin abolished completely negative chronotropic and inotropic effects of oxotremorine in rat atria. These results suggest that NA release from gastric sympathetic nerve terminals is inhibited by activation of muscarinic M2 receptor, and this receptor-mediated inhibitory mechanisms are insensitive to pertussis toxin.
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PMID:Cholinergic M2 muscarinic receptor-mediated inhibition of endogenous noradrenaline release from the isolated vascularly perfused rat stomach. 842 50

1. In the present study, we examined the cellular mechanism and receptor type responsible for a muscarine-induced inward current (Imi) in neurons of rat dorsolateral septal nucleus (DLSN) using single-microelectrode voltage-clamp and "slice" patch-clamp techniques. 2. Imi was associated with an increase of membrane conductance in 75% of DLSN neurons. There was no voltage-dependence of Imi between -60 and -140 mV; it exhibited a reversal potential of -17.0 +/- 5.3 mV (n = 14) determined by extrapolation of Imi and voltage relationship recorded using whole cell patch recording. Lowering extracellular sodium (26 mM) or potassium (1.4 mM) ions depressed Imi. 3. Imi was concentration dependent; 3 and 100 microM muscarine produced the minimum [22 +/- 4.6 pA, (mean +/- SE) n = 8] and maximum (167 +/- 28 pA, n = 7) responses, respectively. An EC50 was determined to be 15 microM (n = 8). Oxotremorine-methiodide (1-100 microM) also produced an inward current with similar potency compared with muscarine. On the other hand, McN-A-343 and pilocarpine (3-100 microM) did not produce any inward current in DLSN neurons. 4. Atropine (1 microM) completely reduced Im produced by 30 microM muscarine, whereas pirenzepine (PZP) shifted the concentration-response curve for muscarine in a parallel manner to the right. The EC50 for muscarine was shifted to 32, 52, and 204 microM by 0.2, 0.5, and 2 microM PZP, respectively. The apparent Kd value for PZP estimated by Schild plot analysis was 190 nM (n = 5). 5. Methoctramine (1 microM) also competitively depressed Imi; the calculated EC50 values were 26, 41, and 107 microM in concentrations of 0.2, 2, and 10 microM methoctramine, respectively. The apparent Kd for methoctramine was 420 nM. In contrast, AF-DX 116 (1 microM) did not significantly inhibit Imi. 6. Intracellular dialysis with guanosine 5'-O-(3-thiotriphosphate), a nonhydrolyzable analogue of GTP, suppressed irreversibly Imi. Pretreatment of DLSN neurons with pertussis toxin (PTX) did not prevent Imi (n = 8). 7. We suggest that muscarine causes this inward current by activating a M3 subtype of muscarinic receptor, which is coupled to a PTX-insensitive GTP-protein in rat DLSN neurons.
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PMID:Muscarine activates a nonselective cation current through a M3 muscarinic receptor subtype in rat dorsolateral septal nucleus neurons. 889 97

In membranes of the rat frontal cortex, acetylcholine (ACh) and other cholinergic agonists were found to potentiate the stimulation of adenylyl cyclase activity elicited by corticotropin-releasing hormone (CRH). Oxotremorine-M, carbachol and methacholine were as effective as ACh, whereas oxotremorine and arecoline were much less effective. The facilitating effect of Ach was potently blocked by the M1 antagonists R-trihexyphenidyl, telenzepine and pirenzepine and by the M3 antagonists hexahydro-sila-difenidol and p-fluorohexahydro-sila-difenidol, whereas the M2 and M4 antagonists himbacine, methoctramine, AF-DX 116 and AQ-RA 741 were less potent. The mamba venom toxin MT-1, which binds with high affinity to M1 receptors, was also a potent blocker. The pharmacological profile of the muscarinic potentiation of CRH receptor activity was markedly different from that displayed by the muscarinic inhibition of forskolin-stimulated adenylyl cyclase, which could be detected in the same membrane preparations. Moreover, the intracerebral injection of pertussis toxin impaired the muscarinic inhibition of cyclic AMP formation and reduced the Ach stimulation of [35S]GTPgammaS binding to membrane G proteins but failed to affect the facilitating effect on CRH receptor activity. The latter response was also insensitive to the phospholipase C inhibitor U-73122, the protein kinase inhibitor staurosporine and to the inhibitors of arachidonic acid metabolism indomethacin and nordihydroguaiaretic acid. These data demonstrate that in the rat frontal cortex, muscarinic receptors of the M1 subtype potentiate CRH transmission by interacting with pertussis toxin-insensitive G proteins.
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PMID:Identification and characterization of muscarinic receptors potentiating the stimulation of adenylyl cyclase activity by corticotropin-releasing hormone in membranes of rat frontal cortex. 969 30

We have investigated the mechanisms by which stimulation of cardiac muscarinic receptors result in paradoxical stimulatory effects on cardiac function, using cultured neonatal rat ventricular myocytes as a model system. Application of low concentrations of carbachol (CCh) (EC50 = 35 nM) produced an atropine-sensitive decrease in spontaneous contraction rate, while, in cells pretreated with pertussis toxin, higher concentrations of CCh (EC50 = 26 microM) elicited an atropine-sensitive increase in contraction rate. Oxotremorine, an m2 muscarinic acetylcholine receptor (mAChR) agonist, mimicked the negative but not the positive chronotropic response to CCh. Reverse transcription followed by polymerase chain reaction carried out on mRNA obtained from single cells indicated that ventricular myocytes express mRNA for the m1, m2, and, possibly, m4 mAChRs. The presence of m1 and m2 mAChR protein on the surface membranes of the cultured ventricular myocytes was confirmed by immunofluorescence. The CCh-induced positive chronotropic response was significantly inhibited by fluorescein-tagged antisense oligonucleotides directed against the m1, but not the m2 and m4, mAChR subtypes. The response was also inhibited by antisense oligonucleotides against Gqalpha protein. Finally, inhibition of CCh-induced phosphoinositide hydrolysis with 500 microM neomycin or 5 microM U73122 completely abolished the CCh-induced positive chronotropic response. These results are consistent with the stimulatory effects of mAChR activation on the rate of contractions in cultured ventricular myocytes being mediated through the m1 mAChR coupled through Gq to phospholipase C-induced phosphoinositide hydrolysis.
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PMID:Signaling mechanisms underlying muscarinic receptor-mediated increase in contraction rate in cultured heart cells. 982 93

The intrathecal administration of pertussis toxin (PTX) not only blocks the antinociceptive effects of the muscarinic cholinergic receptor agonist oxotremorine administered systemically, but also produces a long-lasting thermal allodynia in mice. The purpose of the present studies was to determine both the antinociceptive effects in normal mice and the antiallodynic effects in PTX-treated mice of systemically administered muscarinic cholinergic receptor agonists and cholinesterase inhibitors. In normal mice, antinociceptive effects were tested using a 55 degrees C water-bath tail-flick test. In mice treated 7 days previously with PTX (0.3 microg i.t.), antiallodynic effects were tested using a 45 degrees C water-bath tail-flick test. The nonselective high-efficacy muscarinic agonists oxotremorine, H-TZTP (3-(1,2, 5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine oxalate), and methylthio[2.2.1], (exo (+)3-(3-methylthio-1,2, 5-thiadiazol-4-yl)-1-azabicyclo[2.2.1]heptane oxalate), as well as vedaclidine, a mixed M(2)/M(4) muscarinic receptor partial agonist and M(1)/M(3)/M(5) muscarinic receptor antagonist, the nonselective partial agonists RS86 and pilocarpine, and the cholinesterase inhibitors physostigmine and tacrine all produced dose-related antinociception. Oxotremorine, H-TZTP and methylthio[2.2.1] produced dose-related reversals of PTX-induced thermal allodynia whereas vedaclidine produced a partial reversal and RS86 and pilocarpine, as well as physostigmine and tacrine, failed to reverse the allodynia. The present results provide further evidence that decrements in PTX-sensitive G(i/o)-protein functioning may be involved in initiating and/or maintaining some persistent or neuropathic pain states. Moreover, the present results suggest that muscarinic receptor agonists such as vedaclidine may be useful in the treatment of persistent pain states that are due at least in part to dysfunction of inhibitory second messenger systems.
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PMID:Reversal of pertussis toxin-induced thermal allodynia by muscarinic cholinergic agonists in mice. 1097 34

We compared the binding properties of selective muscarinic antagonists with their potencies for antagonizing muscarinic responses in Chinese hamster ovary (CHO) cells expressing M(2) and M(3) muscarinic receptors in combination and in isolation. When measured by the competitive displacement of [3H]N-methylscopolamine binding to CHO cells expressing both M(2) and M(3) muscarinic receptors (CHO M(2)+M(3) cells), the competition curves of the subtype-selective muscarinic antagonists were consistent with a two-site model. One site exhibited binding properties identical to those of CHO M(2) cells, whereas the other site exhibited properties like those of CHO M(3) cells. Oxotremorine-M, a muscarinic agonist, elicited a robust, pertussis toxin-insensitive stimulation of phosphoinositide hydrolysis in both CHO M(3) and CHO M(2)+M(3) cells, but not in CHO M(2) cells. The pharmacological antagonism of the phosphoinositide response exhibited similar properties in both CHO M(3) and CHO M(2)+M(3) cells. Oxotremorine-M elicited a pertussis toxin-sensitive, robust inhibition of forskolin-stimulated cyclic AMP (cAMP) accumulation in both CHO M(2) and CHO M(2)+M(3) cells and a less robust inhibition in CHO M(3) cells. At higher concentrations, oxotremorine-M elicited an increase in cAMP accumulation over the maximal inhibition noted at lower concentrations in both CHO M(3) and CHO M(2)+M(3) cells. Following pertussis toxin treatment, only the stimulatory phase of the cAMP response to oxotremorine-M was observed in CHO M(2), CHO M(3), and CHO M(2)+M(3) cells. The pharmacological antagonism of the cAMP response in CHO M(2)+M(3) cells resembled that expected for a response mediated independently by both M(2) and M(3) receptors.
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PMID:Comparison of the pharmacological antagonism of M2 and M3 muscarinic receptors expressed in isolation and in combination. 1269 64

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