The vesicular acetylcholine transport system

doi:10.1016/0166-2236(87)90044-0

Trends in Neurosciences

Volume 10, Issue 4, April 1987, Pages 174-177

https://doi.org/10.1016/0166-2236(87)90044-0 Get rights and content

Abstract

In recent years an acetylcholine uptake mechanism has been described in isolated synaptic vesicles. The drug 2-(4-phenylpiperidino) cyclohexanol (AH5183; vesamicol) has been shown to be a potent inhibitor of vesicular acetylcholine storage. Vesamicol acts in a stereoselective non-competitive manner at a site distinct from the transport ATPase and the acetylcholine transporter active site. The drug represents the prototype of a new series of pharmacological agents used to investigate prejunctional cholinergic transmission.

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Cited by (156)

Do spiroindolines have the potential to replace vesamicol as lead compound for the development of radioligands targeting the vesicular acetylcholine transporter?
2017, Bioorganic and Medicinal Chemistry
Citation Excerpt :
Noninvasive in vivo imaging based on radiolabeled VAChT ligands using PET (positron emission tomography) or SPECT (single-photon emission computed tomography) is a promising option for visualization of such cholinergic neuronal processes and thus might support early diagnostics of AD.7,8 So far, the development of VAChT radiotracers is based on vesamicol (trans-2-(4-phenylpiperidino)cyclohexanol, Fig. 1), the single known chemical lead compound, that binds with high affinity to an allosteric site of the transporter.9,10 However, radiolabeled vesamicol itself is not suitable for specific VAChT imaging due to its insufficient selectivity caused by the additional binding to the σ1 and σ2 receptors11,12, which are both as well expressed in cholinergic brain regions.
The vesicular acetylcholine transporter (VAChT) is an important target for in vivo imaging of neurodegenerative processes using positron emission tomography (PET). So far the development of VAChT PET radioligands is based on the single known lead compound vesamicol. In this study we investigated a recently published spiroindoline based compound class (Sluder et al., 2012), which was suggested to have potential in the development of VAChT ligands. Therefore, we synthesized a small series of N,N-substituted spiro[indoline-3,4′-piperidine] derivatives and determined their in vitro binding affinities toward the VAChT. In order to investigate the selectivity, the off-target binding toward σ₁ and σ₂ receptors was determined. The compounds possessed VAChT affinities with K_i values in the range of 39–376 nM. Binding affinities toward the σ₁ and σ₂ receptors are in a similar range indicating that the strong structural difference between the spiroindolines and vesamicol did not improve the selectivity. The observed potential to additionally bind to σ receptors let us assume that the herein investigated spiroindolines are not suitable to replace vesamicol as lead compound for the development of VAChT ligands.
New systematically modified vesamicol analogs and their affinity and selectivity for the vesicular acetylcholine transporter - A critical examination of the lead structure
2015, European Journal of Medicinal Chemistry
Citation Excerpt :
Nevertheless, PET, with fluorine-18 as the currently most widely used radionuclide, is superior regarding its detection efficiency, spatial resolution, and quantification. The previous development of VAChT radiotracers was based on the single known chemical lead compound vesamicol (trans-2-(4-phenylpiperidino)cyclohexanol), that binds with high affinity to an allosteric site of the transporter [11–13]. However, vesamicol also demonstrates substantial affinity to the sigma receptors σ1 and σ2, which are distributed in cholinergic brain regions, thereby impairing the possibility of specific in vivo imaging [14,15].
To verify vesamicol as lead structure in the development of radioligands for imaging of VAChT in the brain by PET, we systematically modified this molecule and investigated four different groups of derivatives. Structural changes were conducted in all three ring systems A, B, and C resulting in a library of different vesamicol analogs. Based on their in vitro binding affinity toward VAChT as well as σ₁ and σ₂ receptors, we performed a structure-affinity relationship (SAR) study regarding both affinity and selectivity. The compounds possessed VAChT affinities in the range of 1.32 nM (benzovesamicol) to >10 μM and selectivity factors from 0.1 to 73 regarding σ₁ and σ₂ receptors, respectively. We could confirm the exceptional position of benzovesamicols as most affine VAChT ligands. However, we also observed that most of the compounds with high VAChT affinity demonstrated considerable affinity in particular to the σ₁ receptor. Finally, none of the various vesamicol analogs in all four groups showed an in vitro binding profile suitable for specific VAChT imaging in the brain.
Cyclodextrins-based enantioselective, potentiometric membrane electrodes for l-vesamicol assay in serum samples
2006, Sensors and Actuators, B: Chemical
Four enantioselective, potentiometric membrane electrodes based on cyclodextrins (α-, β-, γ- and 2-hydroxy-3-trimethylammoniopropyl-β-cyclodextrin (as chlorine salt) (β-derivative-cyclodextrins)) have been constructed for the analysis of l-vesamicol. The linear concentration ranges for the proposed EPMEs based on cyclodextrins were from 10⁻⁹ to 10⁻⁷ mol l⁻¹ for those electrodes based on α-, β- and β-derivative-cyclodextrins with detection limits of 5.7 × 10⁻¹⁰, 2.42 × 10⁻¹⁰ and 4.77 × 10⁻¹⁰ mol l⁻¹, respectively, while γ-cyclodextrin-based electrode is characterized by linear concentration range 10⁻⁵ to 10⁻² mol l⁻¹ with detection limit of 7.86 × 10⁻⁶ mol l⁻¹. The electrodes displayed near-Nernstian slopes of 52–59 mV per decade of l-vesamicol concentration. The electrodes were used for the direct assay of l-vesamicol in serum samples and proved to be reliable, reproducible and stable. The surface of the electrodes can be simply renewed by polishing on alumina paper to obtain a fresh surface ready for use in a new test.
Evaluation of (+)-p-[<sup>11</sup>C]methylvesamicol for mapping sigma<inf>1</inf> receptors: a comparison with [<sup>11</sup>C]SA4503
2006, Nuclear Medicine and Biology
Vesamicol is a leading compound for positron emission tomography (PET) and single photon emission computed tomography (SPECT) tracers for mapping the vesicular acetylcholine transporter (VAChT). Recently, we found that (+)-p-methylvesamicol ((+)-PMV) has low affinity for VAChT (K_i=199 nM), but has moderate to high affinity for sigma receptors: K_i=3.0 nM for sigma₁ and K_i=40.7 nM for sigma₂, and that sigma₁-selective SA4503 (K_i=4.4 nM for sigma₁ and K_i=242 nM for sigma₂) has moderate affinity for VAChT (K_i=50.2 nM). In the present study, we examined the potential of (+)-[¹¹C]PMV as a PET radioligand for mapping sigma₁ receptors as compared with [¹¹C]SA4503. In rat brain, similar regional distribution patterns of (+)-[¹¹C]PMV and [¹¹C]SA4503 were shown by tissue dissection and by ex vivo autoradiography. Blocking experiments using (±)-PMV, (−)-vesamicol, SA4503, haloperidol and (±)-pentazocine showed that the two tracers specifically bound to sigma₁ receptors, and that [¹¹C]SA4503 exhibited greater specific binding than (+)-[¹¹C]PMV. No sign of VAChT-specific binding by [¹¹C]SA4503 was observed in the striatum, which is rich in VAChT sites. In conclusion, (+)-[¹¹C]PMV specifically bound to sigma₁ receptors in the brain, but to a lesser extent than [¹¹C]SA4503, suggesting that (+)-[¹¹C]PMV is a less preferable PET ligand than [¹¹C]SA4503. On the other hand, the moderate affinity of [¹¹C]SA4503 for VAChT is negligible in vivo.
Structural changes of benzylether derivatives of vesamicol and their influence on the binding selectivity to the vesicular acetylcholine transporter
2005, European Journal of Medicinal Chemistry
Citation Excerpt :
Neurodegenerative disorders like Alzheimer's disease as well as physiological ageing processes are characterised by a profound loss of central cholinergic neurons which is accompanied by deficiencies in cholinergic neurotransmission [1–7]. The vesicular acetylcholine transporter (VAChT), localised in cholinergic nerve terminals [8,9], is responsible for the transport of acetylcholine into presynaptic vesicles [10,11]. Therefore, radioligands which bind specifically to the VAChT, are assumed to provide a tool for studying the density of central cholinergic neurons using PET (positron emission tomography) or SPECT (single photon emission computed tomography).
¹⁸F labelled vesamicol analogues, which bind to the vesicular acetylcholine transporter (VAChT) in central cholinergic nerve terminals, are expected to be potential radioligands for the visualisation of cholinergic transmission deficits via positron emission tomography (PET). In this report the regioselective synthesis of five novel vesamicol analogues as well as their in vitro binding properties to the VAChT are described. Beside having the 4-fluorobenzylether-substitution at the cyclohexyl ring as an unique structural feature, the new compounds are additionally modified at the phenyl and piperidine moiety of the vesamicol skeleton. The affinity and selectivity to the VAChT were analysed by competitive binding studies using tritium labelled radioligands. The VAChT affinities (K_i-values) of the novel compounds were estimated ranging between 7.8 ± 3.5 nM and 161.6 ± 17.3 nM, thus some of them are binding with higher affinity to the transporter than vesamicol. However, the compounds tested demonstrated also affinities to the sigma receptors σ₁ and σ₂ ranging between 4.1 ± 1.5 nM and 327.5 ± 75.9 nM. Nevertheless, these data provide the basis for future structure-binding-studies and further underline the potential and usefulness of vesamicol analogues for imaging of the VAChT.
A validated LC method for the determination of vesamicol enantiomers in human plasma using vancomycin chiral stationary phase and solid phase extraction
2004, Journal of Pharmaceutical and Biomedical Analysis
An enantioseparation high performance liquid chromatographic (HPLC) method was developed and validated to determine d-(+)- and l-(−)-vesamicol in human plasma. The assay involved the use of a solid phase extraction for plasma sample clean up prior to HPLC analysis utilizing a C18 Bond-Elute column. Chromatographic resolution of the vesamicol enantiomers was performed on a vancomycin macrocyclic antibiotic chiral stationary phase (CSP) known as Chirobiotic V with a polar ionic mobile phase (PIM) consisting of methanol:glacial acetic acid:triethylamine (100:0.1:0.05 (v/v/v)) at a flow rate of 1.0 ml/min and UV detection set at 262 nm. All analyses were conducted at ambient temperature. The method was validated over the range of 1–20 μg/ml for each enantiomer concentration (R²>0.999). Recoveries for d-(+)- and l-(−)-vesamicol enantiomers were in the ranges of 96–105% at 3–16 μg/ml level. The method proved to be precise (within-run precision ranged from 1.3 to 2.7% and between-run precision ranged from 1.5 to 3.4%) and accurate (within-run accuracies ranged from 0.8 to 3.4% and between-run accuracies ranged from 1.7 to 5.0%). The limit of quantitation (LOQ) and limit of detection (LOD) for each enantiomer in human plasma were 1.0 and 0.5 μg/ml (S/N=3), respectively.

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Trends in Neurosciences

The vesicular acetylcholine transport system

Abstract

Prog. Neurobiol.

Neuroscience

Eur. J. Pharmacol.

J. Biol. Chem.

Brain Res.

Neurosci. Lett.

Brain Res.

J. Biol. Chem.

Brain Res.

Nerve, Muscle and Synapse

J. Neurochem.

J. Cell Biol.

Eur. J. Biochem.

Biochem. Biophys. Res. Commun.