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)

The direct effect of muscarine on neurons of the rat dorsolateral septal nucleus (DLSN) was examined by using conventional microelectrode and voltage-clamp techniques. Muscarine (1-50 microM) caused a hyperpolarization accompanied by an increase of a voltage-independent potassium conductance. Pirenzepine competitively antagonized the muscarine-induced hyperpolarization with an apparent dissociation constant (Kd) value of 54 nM. Furthermore, intracellular loading with GTP gamma S, a non-hydrolyzable GTP analog, blocked irreversibly the muscarine-induced hyperpolarization. In addition, pretreatment of neurons with pertussis toxin (PTX) prevented the hyperpolarization produced by muscarine. These results suggest that muscarine hyperpolarizes DLSN neurons via a voltage-independent potassium conductance by acting at M4 subtype receptors which are coupled to a PTX-sensitive G-protein in DLSN neurons.
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PMID:Muscarine increases a voltage-independent potassium conductance through an M4 receptor in rat dorsolateral septal nucleus neurons. 762 35

The effects of muscarine on whole-cell Ca2+ channel currents in SH-SY5Y cells were studied using conventional and perforated-patch-clamp techniques, with 10 mM Ba2+ as charge carrier. Muscarine (10-300 microM) caused concentration-dependent inhibitions of Ca2+ channel currents which were only reversible when perforated-patch recordings were used. Inhibition of currents was associated with slowing of activation kinetics in approximately 50% of cells. In the presence of 5 microM nifedipine, muscarine was still able to inhibit currents, but after pre-exposure of cells to 1 microM omega-conotoxin GVIA the inhibitory effects of muscarine were almost completely lost. In the presence of 100 microM muscarine, Bay K 8644 (5 microM) was still able to enhance current amplitudes. Pre-treatment of cells with pertussis toxin (250 ng/ml for 16-24 hr) or inclusion of 1 mM GDP-beta-S in the patch-pipette prevented the inhibitory actions of muscarine. Hexahydrosiladifenidol (0.1-1 microM) antagonized the actions of muscarine (calculated pA2 7.1) but the presence of 10 microM pirenzipine or 0.1 microM methoctramine in the bath solution did not alter the degree of current inhibition caused by 100 microM muscarine. In summary, these results indicate that muscarine in SH-SY5Y cells causes inhibition of N-type Ca2+ channels via a M3 receptor coupled to a pertussis toxin-sensitive G-protein.
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PMID:Inhibition of N-type Ca2+ channel currents in human neuroblastoma (SH-SY5Y) cells by muscarine via stimulation of M3 receptors. 763 Apr 87

1. Ca2+ channel modulation by muscarine was investigated in primary cultured embryonic rat hippocampal neurons using the whole-cell variant of the patch-clamp technique. 2. Muscarine produced a reversible and concentration-dependent decrease in the Ba2+ current amplitude. In 65% of neurons sensitive to the agonist, current inhibition was time and voltage dependent, being maximal between -20 and 0 mV and decreasing at depolarizing potentials. In the remaining 35% of neurons, the effects of muscarine were voltage independent, inhibition being constant in a wide potential range between -20 and +80 mV. 3. Different receptors might be involved in the two modes of modulation. Muscarine-induced voltage-dependent inhibition of Ba2+ current was best suppressed by the muscarinic receptor antagonist 4-diphenylacetoxy-N-methyl-piperidine methiodide (81% suppression), while voltage-independent inhibition was best suppressed by AFDX116 (75% suppression). 4. In cells treated with omega-conotoxin (omega-CgTX), the voltage-independent mode of inhibition was strongly prevented, suggesting that the two modulatory mechanisms (voltage dependent and voltage independent) operate on separate classes of high-voltage-activated (HVA) Ca2+ channels. 5. A pertussis toxin-sensitive G-protein is involved in both modes of action of muscarine, since both modes were prevented by pretreatment of the cells with 50 ng ml-1 pertussis toxin. 6. Both modes of modulation were mimicked in different cells by intracellular application of GTP-gamma-S. However, the onset of voltage-independent inhibition was about 5 times slower than that of voltage-dependent inhibition, suggesting involvement of a more complex metabolic pathway for the former mode of channel modulation. 7. Relief of the voltage-dependent inhibition was obtained by depolarizing voltage prepulses and occurred with kinetics that depended on agonist concentration. 8. The voltage-dependent inhibition could be simulated by a kinetic model in which the time course of Ca2+ entry was assumed to be regulated by both the concentration of muscarine and membrane potential.
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PMID:Muscarine inhibits high-threshold calcium currents with two distinct modes in rat embryonic hippocampal neurons. 765 Jun 8

Bath application of the muscarinic receptor agonist, muscarine, produced a concentration-dependent depression of synaptic activity in the dentate gyrus of hippocampal slices. A concentration of 10 microM muscarine produced a reversible depression that could be competitively antagonized by the muscarinic receptor antagonist pirenzepine. However, other muscarinic receptor subtype (M1-M3) antagonists could also block the effects of muscarine. The rank order of antagonist potency was: 4-diphenylacetoxy-N-methyl-piperidine methiodide (M3/M1 antagonist) > pirenzepine (M1) > AFDX-116 (M2). The depression produced by 10 microM muscarine was not affected by in vivo pretreatment with pertussis toxin, and therefore was not mediated by a pertussis toxin-sensitive G-protein. In addition, high concentrations of muscarine did not affect either basal or isoproterenol-stimulated accumulation of cyclic AMP from slices of dentate gyrus. Muscarine also produced a concentration-dependent blockade of the induction of norepinephrine-induced long-lasting potentiation in the dentate gyrus. Norepinephrine-induced long-lasting potentiation is a form of long-lasting plasticity induced in medial perforant path synapses by beta-adrenergic agonists such as isoproterenol. The muscarinic blockade of norepinephrine-induced long-lasting potentiation was also prevented by pretreatment with pirenzepine. Based on these pharmacological data, we conclude that muscarinic depression of evoked responses, as well as blockade of norepinephrine-induced long-lasting potentiation, involves activation of either M3 or M1, but not M2, muscarinic receptors. These data also demonstrate that in addition to modulating normal synaptic transmission, muscarinic receptors may also play an important role in modulating synaptic plasticity.
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PMID:Muscarinic depression of synaptic transmission and blockade of norepinephrine-induced long-lasting potentiation in the dentate gyrus. 768 52

1. Human neuroblastoma (SH-SY5Y) cells were preincubated with [3H]-noradrenaline ([3H]-NA) in the presence of 0.2 mM pargyline to examine the modulation of K(+)-evoked [3H]-NA release by muscarinic agonists. 2. Release of [3H]-NA evoked by 4 min exposure to 100 mM K+ could be partially inhibited by 5 microM nifedipine and partially inhibited by 100 nM omega-conotoxin GVIA (omega-CgTx). When nifedipine and omega-CgTx were added together, evoked release was inhibited by approximately 93%. 3. K(+)-evoked [3H]-NA release was inhibited by > 90% by pretreatment of cells for 2 min with muscarine, carbachol or oxotremorine methiodide (each at 300 microM). For muscarine, inhibition of evoked release was both time- and concentration-dependent and was reversible. Muscarine also inhibited [3H]-NA release evoked by veratridine (28 microM) and replacement of extracellular Ca2+ with Ba2+, but not that evoked by the Ca2+ ionophore, A23187 (19 microM). 4. Residual K(+)-evoked [3H]-NA release measured in the presence of either nifedipine (5 microM) or omega-CgTx (100 nM) was inhibited by muscarine with a similar potency as release evoked in the absence of either Ca2+ channel blocker. Pretreatment of cells for 16-24 h with pertussis toxin (200 ng ml-1) did not affect K(+)-evoked release per se or the ability of muscarine to inhibit such release. 5. Muscarinic inhibition of K(+)-evoked [3H]-NA release was potently antagonized by pirenzepine (pA2 8.14) and by hexahydrosiladiphenidol (pA2 9.03), suggesting the involvement of an M1 receptor. 6. Our results demonstrate that 100 mM K+-evoked release of [3H]-NA from the human neuroblastoma is mediated by activation of both L- and N-type Ca2+ channels. Activation of muscarinic Ml receptors can inhibit release via a pertussis toxin-insensitive mechanism which involves non-selective inhibition of L- and N-type Ca2+ channels.
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PMID:Muscarinic (M1) receptor-mediated inhibition of K(+)-evoked [3H]-noradrenaline release from human neuroblastoma (SH-SY5Y) cells via inhibition of L- and N-type Ca2+ channels. 783 16

1. The effects of acetylcholine (ACh) on pyramidal neurons acutely dissociated from the rat cerebral cortex were studied in the whole-cell mode, by use of the nystatin-perforated patch recording configuration. 2. ACh induced a net inward current (IACh) accompanied by a membrane conductance decrease at a holding potential (VH) of -40 mV. IACh increased in a concentration-dependent manner with a half-maximum concentration (EC50) of 8.7 x 10(-7) M. 3. IACh mainly resulted from the suppression of the voltage- and time-dependent K+ current (M-current). 4. Muscarine and muscarinic agonists such as McN-A-343, oxotremorine and oxotremorine-M mimicked the ACh response. The potency was in the order of oxotremorine-M > McN-A-343 > or = muscarine > oxotremorine. 5. Pirenzepine shifted the concentration-response curve for ACh to the right and the corresponding Schild plot yielded a pA2 value of 7.81. Other muscarinic antagonists also reversibly blocked IACh in a concentration-dependent manner. The inhibitory potency was in the order of atropine > 4-DAMP > pirenzepine > AF-DX-116. 6. IACh could be induced normally even after pre-incubation of dissociated neurones in external solution with 200 ng ml-1 pertussis toxin (PTX) for 8 h, whereas the inhibitory effect of ACh on high-voltage-activated Ca2+ channels was completely abolished by the PTX treatment.
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PMID:Muscarinic acetylcholine response in pyramidal neurones of rat cerebral cortex. 795 77

We studied, in rat sensory neurons, the modulation of high voltage-activated Ca2+ currents (ICa) mediated by the pertussis toxin-sensitive activation of muscarinic receptors, which were found to be of subtypes M2 or M4. Muscarine reversibly blocked somatic Ca2+ spikes but strong predepolarizations only partially relieved the inhibited Ca2+ current. On the other hand, the putative coupling messenger could not rapidly diffuse towards channels whose activity was recorded from a macro-patch. The perforated patch technique virtually prevented the response rundown present during whole-cell experiments. Both omega-conotoxin GVIA (omega-CgTx)-sensitive channels and omega-CgTx- and dihydropyridine-resistant channels are coupled to the muscarinic receptor, but not the L-channel. When measured in the same neuron, dose-response relationships for the first and subsequent agonist applications differed; maximal inhibition, the reciprocal of half-maximal concentration and the Hill coefficient were always highest in the first trial. Muscarine and oxotremorine exhibited monotone dose-response curves, but oxotremorine-M showed non-linear relationships which became monotonic when cells were intracellularly perfused with inhibitors of protein kinase A (PKA) and C (PKC), suggesting that either PKA or receptor-induced PKC could phosphorylate and thus inactive G-proteins or other unknown proteins involved in inhibitory muscarinic actions on ICa. In summary, these data provide a preliminary pharmacological characterization of the muscarinic inhibition of the Ca2+ channels in sensory neurons, with implications about agonist specificity and the interplay between signalling pathways.
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PMID:Muscarinic regulation of Ca2+ currents in rat sensory neurons: channel and receptor types, dose-response relationships and cross-talk pathways. 801 75

1. The effects of acetylcholine (ACh) on granule cells freshly dissociated from rat dentate gyrus (DG) were studied using the nystatin perforated patch technique. This method allowed us to study ACh-induced currents (IACh) under voltage clamp without "run-down" of the ACh response. In some experiments, we used the conventional whole-cell method for intracellular application of drugs not permeable to cell membrane. 2. At a holding potential of -40 mV, ACh induced an outward current. The amplitude of IACh increased in a sigmoidal fashion with increasing ACh concentration. The half-maximal response and the Hill coefficient determined from the relation between ACh concentration and response were 4.98 x 10(-7) M and 1.70, respectively. 3. The reversal potential of IACh was close to the K+ equilibrium potential. The IACh was accompanied by an enhancement of the K+ current. 4. Muscarine and McN-A-343 mimicked the ACh response, whereas oxotremorine induced no response. 5. Muscarinic antagonists reversibly suppressed the IACh (10(-5) M) in a concentration-dependent manner, where the values of half-inhibition concentration (IC50) were 1.03 x 10(-6) M for pirenzepine and 2.21 x 10(-5) M for AF-DX-116. 6. Intracellular perfusion with GDP-beta S suppressed the IACh greatly. The IACh persisted in the neurons pretreated with an external solution containing pertussis toxin (IAP) for 18 h. 7. In the neurons perfused with Ca(2+)-free external solution containing 2 mM ethylene glycol-O,O'-bis (beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid and 10 mM Mg2+, the first application of ACh induced the IACh with an amplitude similar to that in the standard solution.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Muscarinic receptor activation of potassium channels in rat dentate gyrus neurons. 828 13

1. Whole-cell recordings were made from cultured cerebellar granule neurons using perforated patch clamp techniques. The primary cultures were prepared using 6- to 9-day-old Sprague-Dawley rats. 2. Neurons in culture for less than 48 h possessed resting membrane potentials of -29 mV. However, neurons in culture for 7 days had much more hyperpolarized resting membrane potentials (-89 mV). Over the same period, these neurons developed an additional component of outward current. 3. This non-inactivating current was activated by depolarization, exhibited outward rectification and reversed close to the potassium equilibrium potential. The kinetics of activation and deactivation were very rapid. 4. Muscarine ((+)-muscarine chloride) reversibly inhibited the current with an EC50 of 0.17 microM. The inhibition by muscarine was unaffected by pre-incubation for 17-20 h with 120 micrograms ml-1 pertussis toxin. 5. The current and its inhibition by muscarine were unaffected by 100 microM Cd2+. In Ca(2+)-free conditions, the current was significantly larger than in 0.5 mM Ca2+, but inhibition by 10 microM muscarine was significantly reduced. 6. The standing outward current was not obviously affected by 50 microM 5-HT, 50 microM noradrenaline, 50 microM 2-chloroadenosine or 5 mM tetraethylammonium. It was reduced by 10 microM La3+, 10 microM Zn2+ and 1 mM Ba2+. 7. Muscarinic agonists increased the input resistance of neurons and shifted the zero current level in the depolarized direction when voltage clamped. This enhanced excitability was evident under current clamp, where 10 microM muscarine depolarized granule neurons such that action potentials became evident.
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PMID:A non-inactivating K+ current sensitive to muscarinic receptor activation in rat cultured cerebellar granule neurons. 886 63

1. Calcium channel modulation by muscarine was investigated in cultured human neuroblastoma SH-SY5Y cells using the whole cell variant of the patch-clamp technique. 2. In SH-SY5Y cells, omega-conotoxin (omega-CgTx)-sensitive, high-voltage-activated Ca2+ current density gradually increased from approximately 1 microA/cm2 in undifferentiated cells to 4 microA/cm2 after approximately 20 days of application of the differentiating agent retinoic acid. 3. In differentiated SH-SY5Y cells, muscarine reversibly decreased high-voltage-activated omega-CgTx-sensitive Ba2+ currents in a concentration-dependent way. Maximum inhibition (approximately 65%) measured at 0 mV was obtained with 30 microM muscarine and the IC50 was 1 microM. 4. Current inhibition obtained with 30 microM muscarine was suppressed by the specific M2 and M3 antagonists AFDX-116 and 4-diphenylacetoxy-N-methyl-piperidine methiodide (0.3 microM; 87% suppression), but not by the M1 antagonist pirenzepine. 5. Muscarine-induced current suppression was prevented by pretreatment of the cells with pertussis toxin and mimicked by intracellular application of guanosine 5'-[gamma-thio]triphosphate. 6. In several cells, muscarinic inhibition was characterized by a clear slowdown of Ba2+ current activation at low test potentials. Both inhibition and slowdown of activation were attenuated at more positive potentials and could be partially relieved by strong conditioning depolarizations. 7. These results indicate that muscarinic inhibition of omega-CgTx-sensitive Ca2+ channel current occurs through activation of specific muscarinic receptors and the modulatory mechanism operates through activation of a guanosine 5'-triphosphate-binding protein sensitive to pertussis toxin. Our results suggest that a blocking molecule interacts in a voltage-dependent manner with the Ca2+ channel without involvement of intracellular Ca2+ mobilization or activation of protein kinase C or cyclic nucleotide protein kinases. A simple model describing the reactions involved is proposed.
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PMID:Muscarine inhibits omega-conotoxin-sensitive calcium channels in a voltage- and time-dependent mode in the human neuroblastoma cell line SH-SY5Y. 898 8


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