Methyllycaconitine citrate

Activation of alpha7 acetylcholine receptors reduces neuropathic pain by decreasing dynorphin A release from microglia.[Pubmed:30898676]

Brain Res. 2019 Mar 18. pii: S0006-8993(19)30155-6.

Dynorphin A is increased in neuropathic pain models. Activation of alpha7 n acetylcholine receptor (nAchR) reduces inflammation and pain. Whether activation of alpha7 nAchR affects dynorphin A release is unknown. The experiments evaluated the proinflammatory effect of dynorphin A in the spinal nerve ligation-induced neuropathic pain models and the effect of alpha7 nAchR activation on the dynorphin A content. alpha7 nAchR agonist, PHA-543613 and its antagonist, Methyllycaconitine citrate were used and dynorphin A content was measured after spinal nerve ligation and in microglia cultures to test the analgesic mechanisms of alpha7 nAchR activation. The results showed that dynorphin A content peaked 3 to 7 days after nerve injury, and dynorphin A anti-serum intrathecal injection decreased IL-beta and TNF-alpha content a week after nerve injury. Activation of alpha7 nAchR by PHA-543613 alleviated neuropathic pain behaviors and decreased dynorphin A concentration in the ipsilateral spinal cords. Also, PHA-543613 decreased dynorphin A release from the microglia cultures to LPS stimulation by activation of alpha7 nAchR. Our results suggest that dynorphin A contribute to the development and maintenance of neuropathic pain and that decreasing dynorphin A content by activation of alpha7 AchR of microglia is a potential therapeutic target for treating neuropathic pain.

Alpha-7 Nicotinic Receptor-Targeted Cinobufagin Induces Antinociception and Inhibits NF-kappaB Signaling Pathway in DRG Neurons.[Pubmed:30247877]

ACS Chem Neurosci. 2018 Oct 5.

Cinobufagin (CBG) has been shown to have antinociceptive properties. Nevertheless, the antinociceptive effect and mechanism of CBG are still unclear. The present study was designed to investigate the antinociceptive effect of CBG in the thermal and chemical pain models and further to explore the molecular target and potential signal pathway. As shown in the hot-plate test, formalin test, and acetic acid writhing test in mice, administration of CBG produced significant antinociceptive activity in a dose-dependent manner, and the antinociceptive effect was blocked by intraperitoneal pretreatment of Methyllycaconitine citrate (an alpha7 nicotinic receptor antagonist) and intrathecal delivery of an alpha7 nicotinic receptor antagonist siRNA (alpha7-siRNA). Immunofluorescence demonstrated that the alpha7 nicotinic receptor and IkappaB/NF-kappaB were coexpressed in primary cultured lumbar DRG neurons. In the chemical pain models and primary cultured DRG neurons, Western blot analysis showed that the formation of p-IkappaB and p-NF-kappaB was regulated by CBG, and the effect of CBG was inhibited by alpha7-siRNA, and ELISA analysis indicated that CBG also regulated the expression of inflammatory cytokines through the alpha7 nicotinic receptor in DRG. These results suggest that CBG may activate an alpha7 nicotinic receptor, thereby triggering the inhibition of the DRG NF-kappaB signaling pathway, resulting in an antinociceptive effect in mice.

Antinociception of the spirocyclopiperazinium salt compound LXM-15 via activating alpha7 nAChR and M4 mAChR and inhibiting CaMKIIalpha/cAMP/CREB/CGRP signalling pathway in mice.[Pubmed:29353067]

Regul Toxicol Pharmacol. 2018 Apr;94:108-114.

The aim of this study was to investigate the analgesic effect of the spirocyclopiperazinium salt compound LXM-15 by intragastric administration in thermal and chemical pain models and further to elucidate the possible molecular mechanisms. The results showed that LXM-15 exerted significant antinociception in hot-plate test, formalin test and acetic acid writhing test. Western blot analysis showed that LXM-15 significantly reduced the upregulation of phosphorylation of calcium/calmodulin -dependent protein kinase IIalpha (CaMKIIalpha) and cAMP response element-binding protein (CREB), and further decreased the elevation of calcitonin gene related peptide (CGRP) in the dorsal root ganglion (DRG) and spinal cord in mice. ELISA analysis showed the level of cAMP in the spinal cord was decreased by LXM-15. All effects of LXM-15 could be blocked by Methyllycaconitine citrate (MLA, a selective alpha7 nicotinic receptor antagonist) or tropicamide (TRO, a selective M4 muscarinic receptor antagonist). This study first reported that intragastric administration of LXM-15 produced significant analgesic effect, which may be related to the activation of alpha7 nicotinic acetylcholine receptor and M4 muscarine acetylcholine receptor, and thereby inhibiting CaMKIIalpha/cAMP/CREB/CGRP signalling pathway.

Anti-inflammatory effect and mechanism of the spirocyclopiperazinium salt compound LXM-15 in rats and mice.[Pubmed:29302720]

Inflamm Res. 2018 Apr;67(4):363-370.

OBJECTIVE: This study aimed to investigate the anti-inflammatory effects of a novel spirocyclopiperazinium salt compound LXM-15, and explore the underlying mechanisms. METHODS: Xylene-induced mouse ear oedema and carrageenan-induced rat paw oedema tests were used to evaluate the anti-inflammatory effects of LXM-15. The protein levels of TNF-alpha, IL-6, phosphorylation of Janus kinase 2 (JAK2) and signal transducer and activator of transcription 3 (STAT3) were detected by ELISA or Western blot analysis. Additionally, receptor blocking test was performed to explore the possible target. RESULTS: Intragastric administration with LXM-15 (2, 1, 0.5 mg/kg in mice, and 6, 3, 1.5 mg/kg in rats) produced distinct anti-inflammatory effects in vivo, the highest inhibition percentage was 60 and 52%, respectively (P < 0.01). Following treatment with LXM-15 (6 mg/kg, i.g.), the levels of TNF-alpha and IL-6 in the rats paws were attenuated by 40 and 41%; and the phosphorylation of JAK2 and STAT3 was restrained by 35 and 45%, respectively (P < 0.01). All effects of LXM-15 were blocked by pretreatment with Methyllycaconitine citrate or tropicamide. CONCLUSION: This study provides the first report that the spirocyclopiperazinium salt compound LXM-15 displays considerable anti-inflammatory effects. The underlying mechanism may be through activating the peripheral alpha7 nicotinic acetylcholine receptor and M4 muscarinic acetylcholine receptor, leading to the inhibition of the JAK2/STAT3 signalling pathway, eventually resulting in the reduction of TNF-alpha and IL-6.

Recombinant Newcastle disease virus rL-RVG enhances the apoptosis and inhibits the migration of A549 lung adenocarcinoma cells via regulating alpha 7 nicotinic acetylcholine receptors in vitro.[Pubmed:28974241]

Virol J. 2017 Oct 3;14(1):190.

BACKGROUND: The aim of this study were to investigate the possible pro-apoptotic mechanisms of the recombinant Newcastle disease virus (NDV) strain rL-RVG, which expresses the rabies virus glycoprotein, in A549 lung adenocarcinoma cells via the regulation of alpha 7 nicotinic acetylcholine receptors (alpha7 nAChRs) and to analyze the relationships between alpha7 nAChR expression in lung cancer and the clinical pathological features. METHODS: alpha7 nAChR expression in A549, LAlpha795, and small-cell lung carcinoma (SCLC) cells, among others, was detected using reverse transcription polymerase chain reaction (RT-PCR). The optimal alpha7 nAChR antagonist and agonist concentrations for affecting A549 lung adenocarcinoma cells were detected using MTT assays. The alpha7 nAChR expression in A549 cells after various treatments was assessed by Western blot, immunofluorescence and RT-PCR analyses. Apoptosis in the various groups was also monitored by Western blot and TUNEL assays, followed by the detection of cell migration via transwell and scratch tests. Furthermore, alpha7 nAChR expression was examined by immunohistochemistry in lung cancer tissue samples from 130 patients and 40 pericancerous tissue samples, and the apoptotis in lung adenocarcinoma tissue was detected by Tunel assay, Then, the expression levels and clinicopathological characteristics were analyzed. RESULTS: Of the A549, LAlpha795, SCLC and U251 cell lines, the A549 cells exhibited the highest alpha7 nAChR expression. The cells infected with rL-RVG exhibited high RVG gene and protein expression. The rL-RVG group exhibited weaker alpha7 nAChR expression compared with the Methyllycaconitine citrate hydrate (MLA, an alpha7 nAChR antagonist) and NDV groups. At the same time, the MLA and rL-RVG treatments significantly inhibited proliferation and migration and promoted apoptosis in the lung cancer cells (P < 0.05). The expression of alpha7 nAChR was upregulated in lung cancer tissue compared with pericancerous tissue (P = 0.000) and was significantly related to smoking, clinical tumor-node-metastases stage, and histological differentiation (P < 0.05). The AI in lung adenocarcinoma tissue in high-medium differentiation group was lower than that in low differentiation group (p < 0.01). CONCLUSIONS: An antagonist of alpha7 nAChR may be used as a molecular target for lung adenocarcinoma therapy. Recombinant NDV rL-RVG enhances the apoptosis and inhibits the migration of A549 lung adenocarcinoma cells by regulating alpha7 nAChR signaling pathways.

The expression, localization and function of alpha7 nicotinic acetylcholine receptor in rat corpus cavernosum.[Pubmed:28836276]

J Pharm Pharmacol. 2017 Dec;69(12):1754-1761.

OBJECTIVES: Alpha7 nicotinic acetylcholine receptor (alpha7-nAChR), an emerging pharmacological target for a variety of medical conditions, is expressed in the most mammalian tissues with different effects. So, this study was designed to investigate the expression, localization and effect of alpha7-nAChR in rat corpus cavernosum (CC). METHODS & KEY FINDINGS: Reverse transcription polymerase chain reaction (RT-PCR) revealed that alpha7-nAChR was expressed in rat CC and double immunofluorescence studies demonstrated the presence of alpha7-nAChR in corporal neurons. The rat CC segments were mounted in organ bath chambers and contracted with phenylephrine (0.1 mum -300 mum) to investigate the relaxation effect of electrical field stimulation (EFS,10 Hz) assessed in the presence of guanethidine (adrenergic blocker, 5 mum) and atropine (muscarinic cholinergic blocker, 1 mum) to obtain non-adrenergic non-cholinergic (NANC) response. Cumulative administration of nicotine significantly potentiated the EFS-induced NANC relaxation (-log EC50 = 7.5 +/- 0.057). Whereas, the potentiated NANC relaxation of nicotine was significantly inhibited with different concentrations of Methyllycaconitine citrate (alpha7-nAChR antagonist, P < 0.05) in preincubated strips. L-NAME (non-specific nitric oxide synthase inhibitor, 1 mum) completely blocked the neurogenic relaxation induced by EFS plus nicotine. CONCLUSION: To conclude alpha7-nAChR is expressed in rat CC and modulates the neurogenic relaxation response to nicotine.

Improved Outcomes of Cardiopulmonary Resuscitation in Rats Treated With Vagus Nerve Stimulation and Its Potential Mechanism.[Pubmed:28800036]

Shock. 2018 Jun;49(6):698-703.

Studies have demonstrated that vagus nerve stimulation (VNS) reduces ischemia/reperfusion injury. In this study, we investigated the protective effects of VNS in a rat model of cardiopulmonary resuscitation (CPR). We further investigated whether the beneficial effects of VNS were dependent on the alpha 7 nicotinic acetylcholine receptor (alpha7nAChR). Forty animals were randomized into four groups and all underwent CPR (n = 10 each): CPR alone (control); VNS during CPR; alpha7nAChR antagonist Methyllycaconitine citrate (MLA) with VNS; alpha7nAChR agonist 3-(2, 4-dimethoxybenzylidene) anabaseine (GTS-21 dihydrochloride) without VNS. The right vagus nerve was exteriorized in all animals. Ventricular fibrillation was induced and untreated for 8 min. Defibrillation was attempted after 8 min of CPR. VNS was initiated at the beginning of precordial chest compressions and continued for 4 h after return of spontaneous circulation (ROSC) in both the VNS and MLA groups. Hemodynamic measurements and myocardial function, including ejection fraction and myocardial performance index, were assessed at baseline, 1 and 4 h after ROSC. The neurological deficit score was measured at 24-h intervals for a total of 72 h. The heart rate was reduced in the VNS and MLA groups, while no difference was found in mean arterial pressure between the four groups. Better post-resuscitation myocardial and cerebral function and longer duration of survival were observed in the VNS-treated animals. The protective effects of VNS could be abolished by MLA and imitated by GTS-21. In addition, VNS decreased the number of electrical shocks and the duration of CPR required. VNS improves multiple outcomes after CPR.

Radiosynthesis and in-vivo evaluation of [125I]IBT: a single-photon emission computed tomography radiotracer for alpha7-nicotinic acetylcholine receptor imaging.[Pubmed:28658053]

Nucl Med Commun. 2017 Aug;38(8):683-693.

AIM: The aim of this study was to develop several novel alpha7-nicotinic acetylcholine receptor (nAChR) radioligands for the early diagnosis and treatment of Alzheimer's disease. PATIENTS AND METHODS: The study reported six compounds and studied the in-vitro receptor binding affinity, and selected the I-labeled IBT with good characteristics as a novel radioligand suitable for studying alpha7-nAChRs. After verifying the stability of the radiotracer [I]IBT, the biodistribution in vivo and regional brain biodistribution studies were carried out in mice. Blocking studies with Methyllycaconitine citrate and nicotine were carried out under control and blocking conditions, and the metabolic stability was assessed in vivo in the plasma, brain, and liver. RESULTS AND CONCLUSION: The results of our study suggested that [I]IBT had affinity for alpha7-nAChRs. The in-vivo evaluation in mice of [I]IBT showed a high brain/blood ratio and excellent metabolic stability. The regional brain distribution studies and the blocking studies showed that it had favorable selectivity and specificity and was a potential alpha7-nAChRs radioligand.

Zingiberis Siccatum Rhizoma, the active component of the Kampo formula Daikenchuto, induces anti-inflammatory actions through alpha7 nicotinic acetylcholine receptor activation.[Pubmed:28656709]

Neurogastroenterol Motil. 2017 Dec;29(12).

BACKGROUND: We previously reported that Daikenchuto (DKT), a gastrointestinal prokinetic Japanese herbal (Kampo) medicine used for the treatment of postoperative ileus (POI), has characteristic potent anti-inflammatory activity. This effect may be partly mediated by the activation of alpha7 nicotinic acetylcholine receptor (nAChR). In this study, we identified the specific herbs in DKT that induce anti-inflammatory action. METHODS: The herbal components of DKT were individually administered orally to each mouse four times before and after intestinal manipulation (IM) was carried out on the distal ileum. The anti-inflammatory activity of each crude drug was subsequently evaluated using immunohistochemical analyses of relevant molecules. KEY RESULTS: Treatment with Zingiberis Siccatum Rhizoma (ZSR) but not the other components inhibited the infiltration of cluster of differentiation 68 (CD68)-positive macrophages as effectively as DKT treatment. Selective alpha7nAChR antagonists, such as Methyllycaconitine citrate, or transient receptor potential ankyrin 1 (TRPA1) antagonists, such as HC-030031, significantly inhibited the amelioration of macrophage infiltration by ZSR. The inhibition of macrophage infiltration by ZSR was abolished in both alpha7nAChR and 5-hydroxytryptamine 4 receptor (5-HT4 R) knockout mice. CONCLUSIONS & INFERENCES: Daikenchuto-induced anti-inflammatory activity, which was mediated by inhibiting macrophage infiltration in POI, is dependent on the effects of ZSR. Zingiberis Siccatum Rhizoma activates TRPA1 channels possibly in enterochromaffin (EC) cells to release 5-HT, which stimulates 5-HT4 R in the myenteric plexus neurons to release ACh, which in turn activates alpha7nAChR on macrophages to inhibit inflammation in POI.

Differential discriminative-stimulus effects of cigarette smoke condensate and nicotine in nicotine-discriminating rats.[Pubmed:26996314]

Behav Brain Res. 2016 Jun 1;306:197-201.

Although it is widely accepted that nicotine plays a key role in tobacco dependence, nicotine alone cannot account for all of the pharmacological effects associated with cigarette smoke found in preclinical models. Thus, the present study aimed to determine the differential effects of the interoceptive cues of nicotine alone versus those of cigarette smoke condensate (CSC) in nicotine-trained rats. First, the rats were trained to discriminate nicotine (0.4mg/kg, subcutaneous [s.c.]) from saline in a two-lever drug discrimination paradigm. Then, to clarify the different neuropharmacological mechanisms underlying the discriminative-stimulus effects in the nicotine and CSC in nicotine-trained rats, either the alpha4beta2 nicotinic acetylcholine receptor (nAChR) antagonist dihydro-beta-erythroidine (DHbetaE; 0.3-1.0mg/kg, s.c.) or the alpha7 nAChR antagonist Methyllycaconitine citrate (MLA; 5-10mg/kg, intraperitoneal [i.p.]) was administered prior to the injection of either nicotine or CSC. Separate set of experiments was performed to compare the duration of action of the discriminative-stimulus effects of CSC and nicotine. CSC exhibited a dose-dependent nicotine generalization, and interestingly, 1.0mg/kg of DHbetaE antagonized the discriminative effects of nicotine (0.4mg/kg) but not CSC (0.4mg/kg nicotine content). However, pretreatment with MLA had no effect. In the time-course study, CSC had a relatively longer half-life in terms of the discriminative-stimulus effects compared with nicotine alone. Taken together, the present findings indicate that CSC has a distinct influence on interoceptive effects relative to nicotine alone and that these differential effects might be mediated, at least in part, by the alpha4beta2, but not the alpha7, nAChR.

Nicotinic modulation of Ca2+ oscillations in rat cortical neurons in vitro.[Pubmed:26843531]

Am J Physiol Cell Physiol. 2016 May 1;310(9):C748-54.

The roles of nicotine on Ca(2+) oscillations [intracellular Ca(2+) ([Ca(2+)]i) oscillation] in rat primary cultured cortical neurons were studied. The spontaneous [Ca(2+)]i oscillations (SCO) were recorded in a portion of the neurons (65%) cultured for 7-10 days in vitro. Application of nicotine enhanced [Ca(2+)]i oscillation frequency and amplitude, which were reduced by the selective alpha4beta2-nicotinic acetylcholine receptors (nAChRs) antagonist dihydro-beta-erythroidine (DHbetaE) hydrobromide, and the selective alpha7-nAChRs antagonist Methyllycaconitine citrate (MLA, 20 nM). DHbetaE reduced SCO frequency and prevented the nicotinic increase in the frequency. DHbetaE somewhat enhanced SCO amplitude and prevented nicotinic increase in the amplitude. MLA (20 nM) itself reduced SCO frequency without affecting the amplitude but blocked nicotinic increase in [Ca(2+)]i oscillation frequency and amplitude. Furthermore, coadministration of both alpha4beta2- and alpha7-nAChRs antagonists completely prevented nicotinic increment in [Ca(2+)]i oscillation frequency and amplitude. Thus, our results indicate that both alpha4beta2- and alpha7-nAChRs mediated nicotine-induced [Ca(2+)]i oscillations, and two nAChR subtypes differentially regulated SCO.

Antinociception of spirocyclopiperazinium salt compound LXM-10-M targeting alpha7 nicotinic receptor and M4 muscarinic receptor and inhibiting CaMKIIalpha/CREB/CGRP signaling pathway in mice.[Pubmed:26658370]

Eur J Pharmacol. 2016 Jan 5;770:92-8.

The present study was designed to investigate the antinociception of spirocyclopiperazinium salt compound LXM-10-M (2,4-dimethyl-9-beta-m-hydroxyphenylethyl-3-oxo-6, 9-diazaspiro [5.5] undecane chloride) in thermal and chemical pain models, and further to explore the molecular target and potential signal pathway. We assessed the antinociception of LXM-10-M in hot-plate test, formalin test and acetic acid writhing test in mice. The possible changes of calcium/calmodulin-dependent protein kinase IIalpha (CaMKIIalpha)/cAMP response element-binding protein (CREB)/calcitonin gene related peptide (CGRP) signaling pathway were detected by Western Blot in mice. Administration of LXM-10-M produced significant antinociception in hot-plate test, formalin test and acetic acid writhing test in mice, with no obvious toxicity. The antinociceptive effects were blocked by pretreatment with Methyllycaconitine citrate (MLA, alpha7 nicotinic receptor antagonist) or tropicamide (TRO, M4 muscarinic receptor antagonist). Western blot analysis showed that the upregulations of p-CaMKIIalpha, p-CREB and CGRP in the spinal cord were reduced by LXM-10-M in chemical pain model in mice, and the effects were blocked by MLA or TRO pretreatment. This is the first paper to report that LXM-10-M exerted significant antinociception, which may be attributed to the activation of alpha7 nicotinic receptor and M4 muscarinic receptor and thereby triggering the inhibition of CaMKIIalpha/CREB/CGRP signaling pathway in mice.

Methyllycaconitine prevents methamphetamine-induced effects in mouse striatum: involvement of alpha7 nicotinic receptors.[Pubmed:16076935]

J Pharmacol Exp Ther. 2005 Nov;315(2):658-67.

In a previous study, we demonstrated that in rat striatal synaptosomes, methamphetamine (METH)-induced reactive oxygen species (ROS) production was prevented by methyllycaconitine (MLA), a specific antagonist of alpha7 neuronal nicotinic acetylcholine receptors (alpha7 nAChR). The aim of this study was to test the influence of MLA on acute METH effects and neurotoxicity in mice, using both in vivo and in vitro models. MLA inhibited METH-induced climbing behavior by 50%. Acute effects after 30-min preincubation with 1 microM METH also included a decrease in striatal synaptosome dopamine (DA) uptake, which was prevented by MLA. METH-induced neurotoxicity was assessed in vivo in terms of loss of striatal dopaminergic terminals (73%) and of tyrosine hydroxylase levels (by 90%) at 72 h post-treatment, which was significantly attenuated by MLA. Microglial activation [measured as 1-(2-chlorophenyl)-N-methyl-N-(1-methylpropyl)-3-isoquinolinecarboxamide binding] was also present at 24 h post-treatment and was fully prevented by MLA, tending to confirm its neuroprotective activity. MLA had no effect on METH-induced hyperthermia. Additionally, flow cytometry assays showed that METH-induced ROS generation occurs inside synaptosomes from mouse striatum. This effect implied release of vesicular DA and was calcium-, neuronal nitric-oxide synthase-, and protein kinase C-dependent. MLA and alpha-bungarotoxin, but not dihydro-beta-erythroidine (an antagonist that blocks nAChR-containing beta2 subunits), fully prevented METH-induced ROS production without affecting vesicular DA uptake. The importance of this study lies not only in the neuroprotective effect elicited by the blockade of the alpha7 nicotinic receptors by MLA but also in that it proposes a new mechanism with which to study METH-induced acute and long-term effects.

Effects of Delphinium alkaloids on neuromuscular transmission.[Pubmed:10525069]

J Pharmacol Exp Ther. 1999 Nov;291(2):538-46.

The Delphinium alkaloids methyllycaconitine (MLA), nudicauline, 14-deacetylnudicauline (14-DN), barbinine, and deltaline were investigated for their effects on neuromuscular transmission in lizards. The substituent at C14 provides the only structural difference among the alkaloids MLA, nudicauline, 14-DN, and barbinine. Deltaline lacks the N-(methylsuccinyl)anthranilic acid at C18 common to the other four alkaloids. Each alkaloid reversibly reduced extracellularly recorded compound muscle action potential (CMAP) amplitudes in a concentration-dependent manner. The IC(50) values for CMAP blockade were between 0.32 and 13.2 microM for the N-(methylsuccinimido)anthranoyllycacotonine-type alkaloids and varied with the C14 moiety; the IC(50) value for deltaline was 156 microM. The slopes of the concentration-response curves for CMAP blockade were similar for each alkaloid except barbinine, whose shallower curve suggested alternative or additional mechanisms of action. Each alkaloid reversibly reduced intracellularly recorded spontaneous, miniature end-plate potential (MEPP) amplitudes. Alkaloid concentrations producing similar reductions in MEPP amplitude were 0.05 microM for 14-DN, 0.10 microM for MLA, 0.50 microM for barbinine, and 20 microM for deltaline. Only barbinine altered the time constant for MEPP decay, further suggesting additional or alternative effects for this alkaloid. MLA and 14-DN blocked muscle contractions induced by exogenously added acetylcholine. All five alkaloids are likely nicotinic receptor antagonists that reduce synaptic efficacy and block neuromuscular transmission. The substituent at C14 determines the potency and possibly the mechanism of nicotinic acetylcholine receptor blockade for MLA, nudicauline, 14-DN, and barbinine at neuromuscular synapses. The lower potency of deltaline indicates that the N-(methylsuccinyl)anthranilic acid at C18 affects alkaloid interactions with nicotinic acetylcholine receptors at neuromuscular junctions.

Methyllycaconitine: a selective probe for neuronal alpha-bungarotoxin binding sites.[Pubmed:2226787]

FEBS Lett. 1990 Sep 17;270(1-2):45-8.

The ability of methyllycaconitine (MLA) to inhibit the binding of [125I]alpha-bungarotoxin to rat brain membranes, frog and human muscle extracts and the human muscle cell line TE671 has been measured. MLA showed a markedly higher affinity for the rat brain site (Ki 1.4 x 10(-9) M) than for the muscle receptors (Ki 10(-5)-10(-6) M). Structure modelling techniques were used to fit the structure of MLA to a nicotinic pharmacophore model. MLA is the first low molecular weight ligand to be shown to discriminate between muscle nicotinic receptors and their alpha-bungarotoxin-binding counterpart in the brain, and as such may be a useful structural probe for pursuing the structural and functional properties of the neuronal protein.