Kinase experiment:

Cultured adult rat dorsal root ganglia neurons in 96-well plates are washed twice with release buffer to initiate the assay. CGRP release is induced by incubation of neurons with capsaicin for 10 min at room temperature. The cultures are preincubated with increasing concentrations of capsazepine or AMG9810 for 15 min, followed by 300 nM capsaicin activation for 10 min at room temperature. The extracellular medium is collected and the CGRP content is determined using a commercially kit[1].

Cell experiment:

To assess cyotoxicity of AMG9810, N/TERT1 cells are treated with different concentrations of AMG9810 (0.25, 0.5, 1, 5 μM) and cultured for various periods of time (24, 48, 72 h). The CellTiter 96 AQueous One Solution is added to each well and then cells are kept in a 37℃, 5% CO2 incubator for 1 h. Absorbance is then measured at 492 and 690 nm with a plate reader[2].

Animal experiment:

Rats: AMG9810 is dissolved in DMSO. Rats are acclimated for 30 to 45 min in a 30×30×30-cm Plexiglas chambers before the intraperitoneal injection of either vehicle (DMSO) or AMG 9810. Injections are made over a 5-s period in the lower right ventral quadrant of the abdomen either 15, 30, or 60 min before intraocular application of capsaicin. Intraocular application of capsaicin (3 μg/20 μL in 10% ethanol/PBS) or vehicle (20 μL in 10% ethanol/PBS) is done with a pipette, and the number of front paw eye wipes is counted over a 5-min period in 1-min intervals [1].

AMG 9810 is a vanilloid receptor 1 (VR1 or TRPV1) antagonist, with IC50 values for human TRPV1 of 24.5±15.7 nM, for rat TRPV1 of 85.6 ±39.4 nM as a competitive antagonist of capsaicin activation. To block protons, its IC50 values for rat TRPV1 is 294±192 nM, for human TRPV1 is 92.7±72.8 nM. To block heat, its IC50 value for rat TRPV1 is 21±17 nM, for human TRPV1 is 15.8±10.8 nM. It can also block endogenous ligands, such as N-arachidonyl dopamine, anandamide and oleoyldopamine [1].

TRPV1 is expressed by peripheral sensory neurons. It is a membrane-bound, nonselective cation channel [1].

In rat dorsal root ganglia neurons with the presence of endogenous TRPV1, 45Ca2+ uptake was induced by capsaicin in a dose-dependent manner, the EC90 value is 300 nM. In a Ca2+-dependent manner, capsaicin induces CGRP release through the activation of TRPV1. Capsaicin at 300 nM induced a greater level of CGRP release from cultured neurons into the media, compared with the basal level. Capsaicin-induced 45Ca2+ uptake and CGRP release was potently blocked by AMG 9810 with IC50 values of 9±6 nM and 6±3 nM, respectively. AMG 9810 alone up to 10 ?M had no effect on the basal 45Ca2+ uptake or CGRP release of exposed neurons [1].

In animals capsaicin induced eye wipes. Intraperitoneally, AMG 9810 at 3, 10, and 30 mg/kg, dose-dependently decrease this effect at 15 min. Treatment with AMG 9810 at 10 and 30 mg/kg, 30 min before capsaicin treatment, statistically significantly reduced the number of eye wipes. Only treatment with AMG 9810 at 30 mg/kg 60 min before capsaicin administration significantly reduced eye wipes. Vehicle did not affect capsaicin-evoked eye wipes [1].

Reference:
[1].  Gavva NR, Tamir R, Qu Y, et al. AMG 9810 [(E)-3-(4-t-butylphenyl)-N-(2, 3-dihydrobenzo[b][1,4] dioxin-6-yl)acrylamide], a novel vanilloid receptor 1 (TRPV1) antagonist with antihyperalgesic properties. J Pharmacol Exp Ther, 2005, 313(1):474-84.