Parameters derived from fitting of data to the Hill Equation with a Hill co-efficient of one.

<p>Parameters derived from fitting of data to the Hill Equation with a Hill co-efficient of one.</p

Proposed model.

<p>A schematic of proposed receptor model for the activation of WT 3α4:2β2 nAChR. The model includes unbound (R), one agonist bound (AR), two agonist bound (A₂R) and three agonist bound (A₃R) receptor states. Intermediate ‘flip’ state (RF), Open state (RO) and desensitized state (RD) are shown. Blue frame includes receptor activation model for agonists (eg. Saz-A and TC-2559) that selective bind at the α4-β2 interface and red frame shows receptor activation for ligands selective for α4-α4 interface (NS9283). Dashed lines and grey states indicate transitions and states not discretely tested in our experiments but are considered likely to exist.</p

Saz-A and TC-2559 act selectively at the α4-β2 interface.

<p><b>A</b> Schematic showing α4-β2 (black arrow) and α-α (grey arrow) binding sites for ACh at the 3α4:2β2, 2α4:3β2 and 3α4:2β2^HQT receptors. <b>B.</b> Current traces of Saz-A (1μM) and <b>C.</b> TC-2559 (10μM) for 3α4:2β2, 2α4:3β2 and 3α4:2β2^HQT receptor compared to maximum ACh currents on the same oocyte. Peak currents elicited by <b>D</b> Saz-A and <b>E</b> TC-2559 were normalized to the saturating concentration of ACh and fitted to non-linear curve fits. The injection ratios of α4:β2 that correspond to the 3α4:2β2 (blue) and the 2α4:3β2 (red) receptors are 4:1 and 1:4 respectively. Saz-A and TC-2559 do not activate the 3α4:2β2^HQT (green) receptor that has three α4-α4-like interfaces. Dots represent the mean ± s.e.m.</p

Estimation of open probability.

<p><b><i>A</i></b> Schematic depicting the hypothesized areas for NS206 binding [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0161154#pone.0161154.ref034" target="_blank">34</a>]. <b><i>B</i></b> Representative current trace of the response of the 3α4:2β2 receptor to 1 mM ACh (blue) and 1 mM ACh co-applied with 10 μM NS206 to estimate open channel probability. <b><i>C</i></b> The level of NS206 (10μM) positive modulation of ACh currents for the WT. <b><i>D</i></b> Saz-A and <b><i>E</i></b> TC-2559 concentration-response curves in the absence (blue) and presence (green) of 10 μM NS9283 normalized to 1 mM ACh co-applied with 10 μM NS206 (Est <i>P</i>_{<i>o</i>,<i>max</i>}) at 3α4:2β2 receptors. Dots represent the mean ± s.e.m.</p

Ligand Binding at the α4-α4 Agonist-Binding Site of the α4β2 nAChR Triggers Receptor Activation through a Pre-Activated Conformational State - Fig 2

<p>Saz-A and TC-2559 co-application with NS9283: <b>A</b> Schematic of the 3α4:2β2 receptor with the binding sites of Saz-A and TC-2559 at the α4-β2 interface, and NS9283 at the α4-α4 interface. Representative current trace of <b><i>B</i>.</b> Saz-A and <b><i>C</i>.</b> TC-2559, co-applied with NS9283 (10μM) (Green) compared to max ACh (1mM) current on 3α4:2β2 receptors <b><i>D</i></b> Saz-A and <b><i>E</i></b> TC-2559 concentration-response curves in the absence (blue) and presence (green) of 10 μM NS9283 normalized to 1 mM ACh at 3α4:2β2 receptors. Dots represent the mean ± s.e.m.</p

Kinetic equilibrium constants derived from three-step models proposed.

<p>Kinetic equilibrium constants derived from three-step models proposed.</p

Tying up Nicotine: New Selective Competitive Antagonist of the Neuronal Nicotinic Acetylcholine Receptors

Conformational restriction of the pyrrolidine nitrogen in nicotine by the introduction of an ethylene bridge provided a potent and selective antagonist of the α4β2-subtype of the nicotinic acetylcholine receptors. Resolution by chiral SFC, pharmacological characterization of the two enantiomers, and determination of absolute configuration via enantioselective synthesis showed that the pharmacological activity resided almost exclusively in the (<i>R</i>)-enantiomer