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  1. Chung LY, Yap KF, Goh SH, Mustafa MR, Imiyabir Z
    Phytochemistry, 2008 May;69(7):1548-54.
    PMID: 18334259 DOI: 10.1016/j.phytochem.2008.01.024
    The bark extract of Melicope subunifoliolata (Stapf) T.G. Hartley showed competitive muscarinic receptor binding activity. Six polymethoxyflavones [melibentin (1); melisimplexin (3); 3,3',4',5,7-pentamethoxyflavone (4); meliternatin (5); 3,5,8-trimethoxy-3',4',6,7-bismethylenedioxyflavone (6); and isokanugin (7)] and one furanocoumarin [5-methoxy-8-geranyloxypsoralen (2)] were isolated from the bark extract. Compounds 2 and 6 were isolated for the first time from M. subunifoliolata. The methoxyflavones (compounds 1, 3, 4, 5, 6, and 7) show moderate inhibition in a muscarinic receptor binding assay, while the furanocoumarin (compound 2) is inactive. The potency of the methoxyflavones to inhibit [(3)H]NMS-muscarinic receptor binding is influenced by the position and number of methoxy substitution. The results suggest these compounds are probably muscarinic modulators, agonists or partial agonists/antagonists.
    Matched MeSH terms: Receptors, Muscarinic/metabolism*
  2. Amend N, Niessen KV, Seeger T, Wille T, Worek F, Thiermann H
    Ann N Y Acad Sci, 2020 11;1479(1):13-28.
    PMID: 32198755 DOI: 10.1111/nyas.14336
    Although 193 states have committed to the Chemical Weapons Convention and 98% of the declared chemical weapons stockpiles have been destroyed so far, nerve agent poisoning remains a lingering threat. The recent dissemination of sarin in Syria, the assassination of Kim Jong-Nam in Malaysia, and the assault on Sergei Skripal in the United Kingdom underline the need for effective treatment. The current therapeutic options of a muscarinic receptor antagonist, an oxime, and an anticonvulsant have been unchanged for decades. Therefore, new therapeutic strategies, for example, bioscavengers and receptor-active substances, are promising concepts that have to be examined for their benefits and limitations. In order to facilitate rapid diagnosis in challenging clinical situations, point-of-care diagnostics and detection are of importance. Therapeutic guidance concerning the duration and success of the current oxime therapy via determination of the cholinesterase status can contribute to an optimal use of resources. In summary, the challenges of current and future therapies for nerve agent poisoning and key diagnostic devices will be discussed.
    Matched MeSH terms: Receptors, Muscarinic
  3. Ameer OZ, Salman IM, Siddiqui MJ, Yam MF, Sriramaneni RN, Sadikun A, et al.
    J Acupunct Meridian Stud, 2009 Dec;2(4):288-93.
    PMID: 20633504 DOI: 10.1016/S2005-2901(09)60070-4
    This study aimed to elucidate the mechanism(s) of the spasmogenic action of Loranthus ferrugineus in isolated guinea pig ileum. Thus the contractile responses of guinea pig ileum to graded additions of either L. ferrugineus methanol extract or its n-butanol fraction were tested in the presence and absence of various pharmacological interventions. The data showed that L. ferrugineus methanol extract and the n-butanol fraction produced a concentration-dependent spasmogenic effect in isolated guinea pig ileum segments. These effects were significantly inhibited in the presence of 1 microM atropine. In contrast, the response to the lowest concentrations of L. ferrugineus methanol extract (0.25, 0.5 and 1 mg/mL) and n-butanol fraction of L. ferrugineus (0.125, 0.25 and 0.5 mg/mL) were considerably enhanced in the presence of 0.05 microM neostigmine. Neither L. ferrugineus methanol extract nor n-butanol fraction contractile responses were affected upon the incubation of the ileal segments with 100 microM hexamethonium. The results of this study show that the spasmogenic effect of L. ferrugineus is possibly mediated through a direct action on intestinal muscarinic receptors. It is suggested that the bioactive constituents of L. ferrugineus serve as a substrate for acetylcholinesterase.
    Matched MeSH terms: Receptors, Muscarinic/metabolism
  4. Zakaria ZA, Hassan MH, Nurul Aqmar MN, Abd Ghani M, Mohd Zaid SN, Sulaiman MR, et al.
    Methods Find Exp Clin Pharmacol, 2007 Oct;29(8):515-20.
    PMID: 18040526
    This study was carried out in mice to determine the nonopioid receptor signaling pathway(s) that might modulate the antinociceptive activity of the aqueous and chloroform extracts of Muntingia calabura (M. calabura) leaves, using the hot-plate test. The leaves of M. calabura were sequentially soaked [1:2 (w/v); 72 h] in distilled water (dH(2)O) and chloroform. The 50% concentration extracts were selected for this study based on the plant's previously established antinociceptive profiles. The mice (n = 7) were pretreated (s.c.) for 10 min with the selected nonopioid receptor antagonists, followed by the (s.c.) administration of the respective extract. The latency of discomfort was recorded at the interval time of 0.5, 1, 2, 3, 4 and 5 h after the extract administration. The 5 mg/kg atropine, 10 mg/kg phenoxybenzamine, 10 mg/kg yohimbine, 10 mg/kg pindolol, 1 mg/kg haloperidol and 10 mg/kg bicuculline caused significant (p < 0.05) reduction in the aqueous extract-induced antinociceptive activity. The 10 mg/kg phenoxybenzamine, 10 mg/kg yohimbine, 10 mg/kg pindolol and 10 mg/kg bicuculline caused significant (p < 0.05) reduction in the chloroform extract-induced antinociceptive activity. In conclusion, the central antinociceptive activity of M. calabura leaves appears to be involved in the modulation of various nonopioid receptor signaling pathways. Its aqueous extract antinociceptive activity is mediated via modulation of the muscarinic, alpha(1)-adrenergic, alpha(2)-adrenergic, beta-adrenergic, dopaminergic and GABAergic receptors, while its chloroform extract activity is mediated via modulation of the alpha(1)-adrenergic, alpha(2)-adrenergic, beta-adrenergic and GABAergic receptors.
    Matched MeSH terms: Receptors, Muscarinic/drug effects; Receptors, Muscarinic/metabolism
  5. Nabishah BM, Morat PB, Kadir BA, Khalid BA
    Gen. Pharmacol., 1991;22(2):389-92.
    PMID: 1647349
    1. Glucocorticosteroid may relieve bronchospasm by mediating changes in the muscarinic receptor concentration and/or its affinity. 2. Cholinergic muscarinic receptors were determined by using Scatchard's plots from radioligand binding assays of 0.13-3.2 nM [3H]quinuclidinyl benzylate binding to the membrane fraction of bronchial smooth muscle (BSM). 3. The concentration of muscarinic receptor in BSM of normal rat was 57 +/- 3 fmol mg protein and the dissociation constant was 0.07 +/- 0.02 nM. Dexamethasone and corticosterone reduced muscarinic receptor concentration to 50-60% of basal with no changes in receptor affinity. No changes were found in rat treated with deoxycorticosterone. 4. These findings suggest that glucocorticoids but not mineralocorticoid relieve bronchospasm at least partly by reducing the cholinergic hypersensitivity.
    Matched MeSH terms: Receptors, Muscarinic/drug effects*
  6. Tew WY, Tan CS, Asmawi MZ, Yam MF
    Eur J Pharmacol, 2020 Aug 05;880:173123.
    PMID: 32335091 DOI: 10.1016/j.ejphar.2020.173123
    Morin (3,5,7,2',4'-pentahydroxyflavone) is a yellow coloured natural flavonoid found in plants of the Moraceae family. This favonoid is easily sources from readily available fruits, vegetables and eve certain beverages. Among the sources that was identified, it is clear that morin is most abundantly found in almond, old fustic, Indian guava, and Osage orange. Multiple studies have suggested that morin has multiple therapeutic actions and possess potential to be a functional potent drug. Previous studies demonstrated that morin is capable of resolving deoxycorticosterone acetate-salt-induced hypertension and possess strong vasorelaxant properties. However, the exact mechanisms remains unknown. Therefore, this study is designed to investigate the in vitro mechanism of morin-induced vasorelaxant effects. The underlying mechanisms of morin's vasorelaxant activities were evaluated on thoracic aortic rings isolated from Sprague-Dawley rats. Results from the study demonstrated morin causing vasodilatory reaction in phenylephrine and potassium chloride pre-contracted endothelium-intact aortic rings with the effect being significantly affected in endothelium-denuded aortic rings. Pre-incubation of the aortic rings with ODQ (selective cGMP-independent sGC inhibitor), indomethacin (nonselective COX inhibitor), L-NAME (endothelial nitric oxide inhibitor), propranolol (β2-adrenegic receptors blocker), and atropine (muscarinic receptors blocker) significantly reduced the vasorelaxant effect of morin. It was also found to be able to reduce the intracellular calcium level by blocking VOCC and calcium intake from the extracellular environment and the intracellular release of calcium from the sarcoplasmic reticulum. The present study showed that the vasorelaxant effect of morin potentially involves the NO/sGC, muscarinic receptors, β2-adrenegic receptors, and calcium channels.
    Matched MeSH terms: Receptors, Muscarinic/physiology
  7. Khalid A, Shakeel R, Justin S, Iqbal G, Shah SAA, Zahid S, et al.
    Curr Drug Targets, 2017;18(13):1545-1557.
    PMID: 28302036 DOI: 10.2174/1389450118666170315120627
    BACKGROUND: Stress is involved in memory impairment through multiple mechanisms, including activation of hypothalamic-pituitary axis, which in turn activates release of corticosterone in blood. Cholinergic system blockade by the muscarinic antagonist, scopolamine, also impairs memory.

    OBJECTIVE: This study aimed to investigate the effect of turmeric (20mg/kg) on learning and memory and cholinergic system in a mouse model of stress along with cholinergic blockade.

    METHODS: Restrained stress was induced and cholinergic receptors were blocked using scopolamine in mice. Animals were treated with turmeric (turmeric rhizome powder which was also subjected to NMR analyses) and learning and social behavior was examined. Effect of turmeric on cholinergic muscarinic receptors (mAChR; M1, M3 and M5) gene expression was assessed by RT-PCR in both pre-frontal cortex and hippocampus.

    RESULTS: Ar-turmerone, curcuminoids and α-linolenic acid were the lead compounds present in turmeric extract. Increased serum corticosterone levels were observed in stressed mice when compared to the control group, while turmeric treatment significantly reduced serum corticosterone level. Turmeric treatment caused an improved learning and memory in Morris water maze test in stressed animals. Social novelty preference was also restored in turmeric treated animals. Following turmeric treatment, M5 expression was improved in the cortex and M3 expression was improved in the hippocampus of stress + scopolamine + turmeric treated group.

    CONCLUSIONS: These findings highlight the therapeutic role of turmeric by increasing the expression of M3, M5 and improving learning and memory. Turmeric can be an effective candidate for the treatment of amnesia caused by the stress.

    Matched MeSH terms: Receptors, Muscarinic/metabolism*
  8. Ibrahim E, Diakonov I, Arunthavarajah D, Swift T, Goodwin M, McIlvride S, et al.
    Sci Rep, 2018 05 08;8(1):7110.
    PMID: 29740092 DOI: 10.1038/s41598-018-25569-4
    Bile acids are recognised as bioactive signalling molecules. While they are known to influence arrhythmia susceptibility in cholestasis, there is limited knowledge about the underlying mechanisms. To delineate mechanisms underlying fetal heart rhythm disturbances in cholestatic pregnancy, we used FRET microscopy to monitor cAMP release and contraction measurements in isolated rodent neonatal cardiomyocytes. The unconjugated bile acids CDCA, DCA and UDCA and, to a lesser extent, CA were found to be relatively potent agonists for the GPBAR1 (TGR5) receptor and elicit cAMP release, whereas all glyco- and tauro- conjugated bile acids are weak agonists. The bile acid-induced cAMP production does not lead to an increase in contraction rate, and seems to be mediated by the RI isoform of adenylate cyclase, unlike adrenaline-dependent release which is mediated by the RII isoform. In contrast, bile acids elicited slowing of neonatal cardiomyocyte contraction indicating that other signalling pathways are involved. The conjugated bile acids were found to be partial agonists of the muscarinic M2, but not sphingosin-1-phosphate-2, receptors, and act partially through the Gi pathway. Furthermore, the contraction slowing effect of unconjugated bile acids may also relate to cytotoxicity at higher concentrations.
    Matched MeSH terms: Receptors, Muscarinic/genetics*
  9. Amy Suzana Abu Bakar, Norhafiza Razali, Mohammad Daniel Shafiq Hassan, Renu Agarwal
    MyJurnal
    Glaucoma is an optic neuropathy characterised by optic nerve degeneration associated with
    visual field defects. It remains the world’s number one cause of irreversible blindness and
    patients usually present at late stage of the disease since it is generally asymptomatic until
    severe. The disease is subdivided into primary and secondary with primary open-angle
    glaucoma (POAG) being the most common type. At present, lowering the intraocular pressure
    (IOP) remains the only proven efficient approach in delaying the onset or preventing the
    progression of the disease. Medical treatment with topical antiglaucoma agents is the
    treatment of choice in open angle glaucoma. The use of antiglaucoma drugs aims to reduce
    IOP by enhancing aqueous humour (AH) outflow, reducing AH production, or both. The choice
    to use any available treatment option should be carefully considered in an attempt to maximise
    benefits and reducing the risk of developing adverse drug reactions. This review highlights the
    six classes of ocular hypotensive agents currently in use for POAG treatment including
    prostaglandin analogues; -adrenergic receptor blockers; -2 adrenergic receptor stimulants;
    carbonic anhydrase inhibitors; muscarinic receptor stimulants; rho kinase inhibitors with
    regards to their mechanism/s of action and potential adverse drug reactions, and
    antiglaucoma fixed drug combinations.
    Matched MeSH terms: Receptors, Muscarinic
  10. Chokhani R, Muttalif AR, Gunasekera K, Mukhopadhyay A, Gaur V, Gogtay J
    Pulm Ther, 2021 Jun;7(1):251-265.
    PMID: 33855650 DOI: 10.1007/s41030-021-00153-w
    INTRODUCTION: There is much recent data from Nepal, Sri Lanka and Malaysia that can help us understand the practice patterns of physicians regarding the diagnosis and management of chronic obstructive pulmonary disease (COPD) in these countries. We conducted this survey to understand the practice patterns of physicians related to the diagnosis and management of COPD in these three countries.

    METHODS: This questionnaire-based, observational, multicentre, cross-sectional survey was carried out with 438 randomly selected physicians consulting COPD patients.

    RESULTS: In the survey, 73.29% of the physicians consulted at least five COPD patients daily (all patients > 40 years of age). 31.14% of the COPD patients visiting their doctors were women. Among physicians, 95.12% reported that at least 70% of their patients were smokers. 34.18% of the physicians did not routinely use spirometry to diagnose COPD. Most physicians preferred a short-acting β2-agonist (SABA) (28.19%) in the Global Initiative for Chronic Obstructive Lung Disease (GOLD) Group-A and long-acting muscarinic receptor antagonist plus long-acting β2-agonist/inhaled corticosteroids (LAMA + LABA/ICS) in both the GOLD Group-C (39.86%) and Group-D (72.89%) patients. A significant number (40.67%) of physicians preferred LABA/LAMA for their GOLD Group-B patients. A pressurised metered dose inhaler (pMDI) with or without spacer was the most preferred device. Only 23.67% of the physicians believed that at least 70% of their patients had good adherence (> 80%) to therapy. Up to 54.42% of the physicians prescribed inhalation therapy to every COPD patient. Also, 39.95% of the physicians evaluated their patients' inhalation technique on every visit. Up to 52.67% of the physicians advised home nebulisation to > 10% of patients, with nebulised SABA/short-acting muscarinic receptor antagonist (SAMA) being the most preferred management choice. Most physicians offered smoking cessation advice (94.16%) and/or vaccinations (74.30%) as non-pharmacological management, whereas pulmonary rehabilitation was offered by a smaller number of physicians. Cost of therapy and poor technique were the most common reasons for non-adherence to COPD management therapy.

    CONCLUSION: Awareness of spirometry can be increased to improve the diagnosis of COPD. Though physicians are following the GOLD strategy recommendations for the pharmacological and non-pharmacological management of COPD, awareness of spirometry could be increased to improve proper diagnosis. Regular device demonstration during each visit can improve the inhalation technique and can possibly increase adherence to treatment.

    Matched MeSH terms: Receptors, Muscarinic
  11. Kan HW, Peng WH, Wu CC, Wang DW, Lee MT, Lee YK, et al.
    Psychopharmacology (Berl), 2022 Dec;239(12):3805-3818.
    PMID: 36221037 DOI: 10.1007/s00213-022-06250-1
    RATIONALE: Clinical reports reveal that scopolamine, an acetylcholine muscarinic receptor antagonist, exerts rapid antidepressant effects in depressed patients, but the mechanisms underlying the therapeutic effects have not been fully identified.

    OBJECTIVES: The present study examines the cellular mechanisms by which scopolamine produces antidepressant-like effects through its action in the ventrolateral midbrain periaqueductal gray (vlPAG).

    METHODS: We used a well-established mouse model of depression induced by chronic restraint stress (CRS) exposure for 14 days. Behaviors were tested using the forced swim test (FST), tail suspension test (TST), female urine sniffing test (FUST), novelty-suppressed feeding test (NSFT), and locomotor activity (LMA). Synaptic transmission in the vlPAG was measured by whole-cell patch-clamp recordings. IntravlPAG microinjection was used to pharmacologically verify the signaling cascades of scopolamine in the vlPAG.

    RESULTS: The results demonstrated that intraperitoneal injection of scopolamine produced antidepressant-like effects in a dose-dependent manner without affecting locomotor activity. CRS elicited depression-like behaviors, whereas intraperitoneal injection of scopolamine alleviated CRS-induced depression-like behaviors. CRS diminished glutamatergic transmission in the vlPAG, while scopolamine reversed the above effects. Moreover, intravlPAG microinjection of the L-type voltage-dependent calcium channel (VDCC) blocker verapamil, tropomyosin-related kinase B (TrkB) receptor antagonist ANA-12, mammalian target of rapamycin complex 1 (mTORC1) inhibitor rapamycin, and α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPA) antagonist CNQX prevented scopolamine-induced antidepressant-like effects.

    CONCLUSIONS: Scopolamine ameliorated CRS-elicited depression-like behavior required activation of VDCC, resulting in activity-dependent release of brain-derived neurotrophic factor (BDNF), engaging the TrkB receptor and downstream mTORC1 signaling in the vlPAG.

    Matched MeSH terms: Receptors, Muscarinic
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