Cell experiment:

RINm5F cells are seeded in 24-well plates and treated with vehicle (DMSO), 10 μM AR-M 1000390 (AR-M100390), and 10 μM Cyclizine in serum-free medium; cells are rinsed with phosphate-buffered saline and stored at -80℃ until analysis. RNA is isolated with the RNeasy purification system with DNAse treatment[2].

Animal experiment:

Rats[2]Han Wistar rats (six per treatment group) are treated with vehicle (saline) or 5, 100, and 600 μmol/kg/day of AR-M 1000390 (AR-M100390) for 7 days. A separate group of rats are treated with 600 μmol/kg/day for 7 days followed by a 14-day recovery period. Another group is treated with 600 μmol/kg/day for 3 days. Blood sampling for glucose, lipids, and insulin measurements are taken on days 2, 4, 8, and 22. Blood sampling for AR-M 1000390 concentration measurements are collected on days 4 and 8. The animals are euthanized with CO2 on days 4, 8, and 22 and the pancreas isolated and processed for histopathology, insulin immunohistochemistry, and insulin mRNA analyses[2].

AR-M 1000390 hydrochloride is a potent and selective agonist of δ-opioid receptor with IC50 value of 0.87 nM [1].

Opioid receptor is a G protein-coupled receptor with opioids as ligands. δ-opioid receptor is a opioid receptor with enkephalins as its endogenous ligands and activation of δ-opioid receptor causes analgesia.

AR-M 1000390 hydrochloride is a potent and selective δ-opioid receptor agonist with IC50 values of 0.87 nM, 3.8 and 7.47 μM for δ-opioid receptor, μ-opioid receptor and κ-opioid receptor, respectively [1]. In the SK-N-BE neuroblastoma cell line, AR-M 1000390 inhibited forskolin-stimulated cAMP accumulation with Ki and EC50 values of 106 and 111 nM, respectively. Sustained activation of opioid receptors by AR-M1000390 produced a strong desensitization [2].

In DOR-eGFP mice, ARM390 (10 mg/kg) significantly reduced CFA-induced heat hyperalgesia at day 1 and induced complete tolerance at day 5. In ARM390-tolerant mice, δ-opioid receptor uncoupled to Ca2+ channels in dorsal root ganglia [3].

References:
[1].  Wei ZY, Brown W, Takasaki B, et al. N,N-Diethyl-4-(phenylpiperidin-4-ylidenemethyl)benzamide: a novel, exceptionally selective, potent delta opioid receptor agonist with oral bioavailability and its analogues. J Med Chem, 2000, 43(21): 3895-3905.
[2].  Marie N, Landemore G, Debout C, et al. Pharmacological characterization of AR-M1000390 at human delta opioid receptors. Life Sci, 2003, 73(13): 1691-1704.
[3].  Pradhan AA, Walwyn W, Nozaki C, et al. Ligand-Directed Trafficking of the
-Opioid Receptor In Vivo: Two Paths Toward Analgesic Tolerance. J Neurosci, 2010, 30(49): 16459-16468.