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Fulltext In vitro cholinomimetic effect of Loranthus ferrugineus in isolated guinea pig ileum

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: Muscarinic Antagonists/pharmacology
Interaction between oxytocin and 'sidaverin' on the gravid and non-gravid rat uterus

Lutterodt GD

Pharmacol Res, 1995 Jul-Aug;32(1-2):89-94.
PMID: 8668653 DOI: 10.1016/S1043-6618(95)80014-X

Sidaverin, a crystalline compound extracted from a polar fraction of Sida veronicaefolia (Lam), elicited oxytocin-like contractions in the non-gravid rat isolated uterus preparation with a concentration-response relationship. Equipotent concentrations of oxytocin and sidaverin, using matched responses, were approximately 0.16 U and 0.4 micrograms ml-1, respectively. Sidaverin-induced contractile response was atropine reversible. The concentration-response curves for sidaverin and oxytocin were parallel, and both responses were inhibited by the specific oxytocin antagonist, Atosiban, indicating possible involvement of oxytocin receptors in the action of sidaverin. There were potentiation of action of one drug to that of the other, irrespective of the order of administration and even after washing off the first before introducing the second drug. In the gravid uterus, sidaverin produced contractions in preparations from day 1 to day 6 or 7, caused relaxation in days 7-11, and elicited contractions in day 11 through term, the sensitivity of the preparations increasing exponentially toward term with strong sustained contractions. With the exception of days 7-11, when sidaverin antagonized oxytocin action, it potentiated action of oxytocin on the gravid uterus.

Matched MeSH terms: Muscarinic Antagonists/pharmacology
Rapid antidepressant-like effects of muscarinic receptor antagonists require BDNF-dependent signaling in the ventrolateral periaqueductal gray

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: Muscarinic Antagonists/pharmacology
Fulltext A Pharmacological Examination of the Cardiovascular Effects of Malayan Krait (Bungarus candidus) Venoms

Chaisakul J, Rusmili MR, Hodgson WC, Hatthachote P, Suwan K, Inchan A, et al.

Toxins (Basel), 2017 03 29;9(4).
PMID: 28353659 DOI: 10.3390/toxins9040122

Cardiovascular effects (e.g., tachycardia, hypo- and/or hypertension) are often clinical outcomes of snake envenoming. Malayan krait (Bungarus candidus) envenoming has been reported to cause cardiovascular effects that may be related to abnormalities in parasympathetic activity. However, the exact mechanism for this effect has yet to be determined. In the present study, we investigated thein vivoandin vitrocardiovascular effects ofB. candidusvenoms from Southern (BC-S) and Northeastern (BC-NE) Thailand. SDS-PAGE analysis of venoms showed some differences in the protein profile of the venoms.B. candidusvenoms (50 µg/kg-100 µg/kg, i.v.) caused dose-dependent hypotension in anaesthetised rats. The highest dose caused sudden hypotension (phase I) followed by a return of mean arterial pressure to baseline levels and a decrease in heart rate with transient hypertension (phase II) prior to a small decrease in blood pressure (phase III). Prior administration of monovalent antivenom significantly attenuated the hypotension induced by venoms (100 µg/kg, i.v.). The sudden hypotensive effect of BC-NE venom was abolished by prior administration of hexamethonium (10 mg/kg, i.v.) or atropine (5 mg/kg, i.v.). BC-S and BC-NE venoms (0.1 µg/kg-100 µg/ml) induced concentration-dependent relaxation (EC50= 8 ± 1 and 13 ± 3 µg/mL, respectively) in endothelium-intact aorta. The concentration-response curves were markedly shifted to the right by pre-incubation with L-NAME (0.2 mM), or removal of the endothelium, suggesting that endothelium-derived nitric oxide (NO) is likely to be responsible for venom-induced aortic relaxation. Our data indicate that the cardiovascular effects caused byB. candidusvenoms may be due to a combination of vascular mediators (i.e., NO) and autonomic adaptation via nicotinic and muscarinic acetylcholine receptors.

Matched MeSH terms: Muscarinic Antagonists/pharmacology
Effects of a neurotensin analogue (PD149163) and antagonist (SR142948A) on the scopolamine-induced deficits in a novel object discrimination task

Azmi N, Norman C, Spicer CH, Bennett GW

Behav Pharmacol, 2006 Jun;17(4):357-62.
PMID: 16914954

Various lines of evidence suggest a role in cognition for the endogenous neuropeptide, neurotensin, involving an interaction with the central nervous system cholinergic pathways. A preliminary study has shown that central administration of neurotensin enhances spatial and nonspatial working memory in the presence of scopolamine, a muscarinic receptor antagonist which induces memory deficits. Utilizing similar methods, the present study employed a two-trial novel object discrimination task to determine the acute effect of a neurotensin peptide analogue with improved metabolic stability, PD149163, on recognition memory in Lister hooded rats. Consistent with previous findings with neurotensin, animals receiving an intracerebroventricular injection of PD149163 (3 microg) significantly discriminated the novel from familiar object during the choice trial. In addition, a similar dose of PD149163 restored the scopolamine-induced deficit in novelty recognition. The restoration effect on scopolamine-induced amnesia produced by PD149163 was blocked by SR142948A, a nonselective neurotensin receptor antagonist, at a dose of 1 mg/kg (intraperitonial) but not at 0.1 mg/kg. In conclusion, the present results confirm a role for neurotensin in mediating memory processes, possibly via central cholinergic mechanisms.

Matched MeSH terms: Muscarinic Antagonists/pharmacology*
Mechanisms underlying the antihypertensive effect of Alstonia scholaris

Bello I, Usman NS, Mahmud R, Asmawi MZ

J Ethnopharmacol, 2015 Dec 4;175:422-31.
PMID: 26429073 DOI: 10.1016/j.jep.2015.09.031

Alstonia scholaris has a long history of use in the Ayurveda traditional treatment of various ailments including hypertension. We have reported the blood pressure lowering activity of the extract of A. scholaris. The following research aim to delineate the pharmacological mechanism involve in the antihypertensive action.

Matched MeSH terms: Muscarinic Antagonists/pharmacology