Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2017 Nov:92:202-209.
doi: 10.1016/j.biocel.2017.10.006. Epub 2017 Oct 16.

Selectivity of coronaridine congeners at nicotinic acetylcholine receptors and inhibitory activity on mouse medial habenula

Affiliations

Selectivity of coronaridine congeners at nicotinic acetylcholine receptors and inhibitory activity on mouse medial habenula

Hugo R Arias et al. Int J Biochem Cell Biol. 2017 Nov.

Abstract

The inhibitory activity of coronaridine congeners on human (h) α4β2 and α7 nicotinic acetylcholine receptors (AChRs) is determined by Ca2+ influx assays, whereas their effects on neurons in the ventral inferior (VI) aspect of the mouse medial habenula (MHb) are determined by patch-clamp recordings. The Ca2+ influx results clearly establish that coronaridine congeners inhibit hα3β4 AChRs with higher selectivity compared to hα4β2 and hα7 subtypes, and with the following potency sequence, for hα4β2: (±)-18-methoxycoronaridine [(±)-18-MC]>(+)-catharanthine>(±)-18-methylaminocoronaridine [(±)-18-MAC] ∼ (±)-18-hydroxycoronaridine [(±)-18-HC]; and for hα7: (+)-catharanthine>(±)-18-MC>(±)-18-HC>(±)-18-MAC. Interestingly, the inhibitory potency of (+)-catharanthine (27±4μM) and (±)-18-MC (28±6μM) on MHb (VI) neurons was lower than that observed on hα3β4 AChRs, suggesting that these compounds inhibit a variety of endogenous α3β4* AChRs. In addition, the interaction of bupropion with (-)-ibogaine sites on hα3β4 AChRs is tested by [3H]ibogaine competition binding experiments. The results indicate that bupropion binds to ibogaine sites at desensitized hα3β4 AChRs with 2-fold higher affinity than at resting receptors, suggesting that these compounds share the same binding sites. In conclusion, coronaridine congeners inhibit hα3β4 AChRs with higher selectivity compared to other AChRs, by interacting with the bupropion (luminal) site. Coronaridine congeners also inhibit α3β4*AChRs expressed in MHb (VI) neurons, supporting the notion that these receptors are important endogenous targets for their anti-addictive activities.

Keywords: (+)-Catharanthine; 18-Methoxycoronaridine; Brain slices; Coronaridine congeners; Medial habenula; Nicotinic acetylcholine receptor.

PubMed Disclaimer

Figures

Fig. 1
Fig. 1
Molecular structure of coronaridine congeners in the protonated state, including (−)-18-MC [(−)-18-methoxycoronaridine], (−)-18-HC [(−)-18-hydroxycoronaridine], (−)-18-MAC [(−)-18-methylaminocoronaridine], and (+)-catharanthine [(+)-3,4-didehydrocoronaridine].
Fig. 2
Fig. 2
Effect of coronaridine congeners on (±)-epibatidine-induced Ca2+ influx in HEK293-hα4β2 cells. Increased concentrations of (±)-epibatidine (■) activated hα4β2 AChRs with potency EC50 = 12 ± 5 nM (n = 25). Subsequently, cells were pre-treated (5 min) with several concentrations of (+)-catharanthine (▲), (±)-18-MC (○), (±)-18-MAC (□), and (±)-18-HC (●), followed by addition of 0.1 μM (±)-epibatidine. Response was normalized to the maximal (±)-epibatidine response which was set as 100%. The plots are representative of four determinations, where the error bars are the S.D. The calculated IC50 and nH values are summarized in Table 1.
Fig. 3
Fig. 3
Effect of coronaridine congeners on (±)-epibatidine-induced Ca2+ influx in GH3-hα7 cells. Increased concentrations of (±)-epibatidine (■) activated hα7 AChRs with potency EC50 = 26 ± 4 nM (n = 25). Subsequently, cells were pre-treated (5 min) with several concentrations of (+)-catharanthine (▲), (±)-18-MC (○), (±)-18-MAC (□), and (±)-18-HC (●), followed by addition of 1.0 μM (±)-epibatidine. Response was normalized to the maximal (±)-epibatidine response which was set as 100%. The plots are representative of four determinations, where the error bars are the S.D. The calculated IC50 and nH values are summarized in Table 1.
Fig. 4
Fig. 4
Inhibitory potency of (±)-18-MC on ACh-evoked currents from MHb (VI) neurons. (A) ACh puffer (100 μM)-evoked currents from MHb (VI) neurons are decreased by 180 μM (±)-18-MC. The puffer was performed for 250 ms at a pressure of 12 psi. After washing (13 min), the peak amplitude reached the same levels as that observed in control neurons, indicating a reversible inhibition. (B) Concentration-response relationship for the inhibitory activity of (±)-18-MC on ACh-evoked currents from MHb (VI) neurons. Response was normalized to the maximal ACh response which was set as 100%. The plot (r2 = 0.80) is representative of 5–7 determinations, where the error bars are the S.D. The calculated IC50 and nH values are summarized in Table 2.
Fig. 5
Fig. 5
Inhibitory potency of (+)-catharanthine on ACh-evoked currents from MHb (VI) neurons. (A) ACh puffer (100 μM)-evoked currents from MHb (VI) neurons are decreased by 180 μM (+)-catharanthine. The puffer was performed for 250 ms at a pressure of 12 psi. After washing (10 min), the peak amplitude reached the same levels as that observed in control neurons, indicating a reversible inhibition. (B) Concentration-response relationship for the inhibitory activity of (+)-catharanthine on MHb (VI) neurons. Response was normalized to the maximal ACh response which was set as 100%. The plot (r2 = 0.87) is representative of 4–7 determinations, where the error bars are the S.D. The calculated IC50 and nH values are summarized in Table 2.
Fig. 6
Fig. 6
Bupropion-induced inhibition of [3H]ibogaine binding to hα3β4 AChRs in the resting (□) and desensitized (○) states, respectively. hα3β4 AChR membranes (1.5 mg/mL) were pre-incubated (30 min) with 16.6 nM [3H]ibogaine in the absence (receptors are mainly in the resting state) and presence of 1 μM (−)-nicotine (receptors are mainly in the desensitized state), and then equilibrated with increasing concentrations of bupropion. Nonspecific binding was determined at 100 μM (−)-ibogaine. The plots are combinations of two experiments, each performed in triplicate, where the error bars are the S.D. The IC50 and nH values were obtained by nonlinear least-squares fit of the plots (r2 = 0.95 for both). The Ki values, calculated using eq. 1 and summarized in Table 3, indicated that bupropion binds to desensitized hα3β4 AChRs with higher affinity than that at resting receptors (Student t-test p = 0.001).
Fig. 7
Fig. 7
Model of the hα3β4 AChR transmembrane domain showing the ion channel lumen (modified from Arias et al., 2010b). (−)-Ibogaine (cyan) interacts with a luminal site formed between the phenylalanine/valine (position 13′) and serine (position 6′) rings (Arias et al., 2010b), which overlaps the site for (−)-bupropion (magenta) (Arias et al., submitted manuscript). The AChR and ligands are depicted by its solvent accessible surface.

Similar articles

Cited by

References

    1. Alper KR, Lotsof HS, Kaplan CD. The ibogaine medical subculture. J Ethnopharmacol. 2008;115:9–24. - PubMed
    1. Arias HR, Rosenberg A, Feuerbach D, Targowska-Duda KM, Maciejewski R, Moaddel R, Glick SD, Wainer IW. Interaction of 18-methoxycoronaridine with nicotinic acetylcholine receptors in different conformational states. Biochem Biophys Acta. 2010a;1798:1153–1163. - PMC - PubMed
    1. Arias HR, Rosenberg A, Targowska-Duda KM, Feuerbach D, Yuan XJ, Jozwiak K, Moaddel R, Wainer IW. Interaction of ibogaine with human α3β4-nicotinic acetylcholine receptors in different conformational states. Int J Biochem Cell Biol. 2010b;42:1525–1535. - PMC - PubMed
    1. Arias HR, Feuerbach D, Targowska-Duda KM, Russell M, Jozwiak K. Interaction of selective serotonin reuptake inhibitors with neuronal nicotinic acetylcholine receptors. Biochemistry. 2010c;49:5734–5742. - PubMed
    1. Arias HR, Targowska-Duda KM, Feuerbach D, Sullivan CJ, Maciejewski R, Jozwiak K. Different interaction between tricyclic antidepressants and mecamylamine with the human α3β4 nicotinic acetylcholine receptor ion channel. Neurochem Int. 2010d;56:642–649. - PubMed

Publication types

LinkOut - more resources