| In Vitro | In vitro activity: JTC-801 displays about 12.5-, 129-, and 1055-fold selectivity for ORL1 receptor (Ki = 8.2 nM) over μ-, κ-, and δ-opioid receptors, respectively. JTC-801 does not inhibit forskolin-stimulated cyclic AMP accumulation in human ORL1 receptor-expressing HeLa cells, but it prevents nociceptin-induced inhibition of cyclic AMP accumulation, indicating that JTC-801 possesses full antagonistic activity. In rat cerebrocortical membrane, JTC-801 inhibits ORL1 receptor with IC50 of 472 nM and μ-receptor with IC50 of 1831 nM. JTC-801 completely antagonizes the suppression of nociceptin on forskolin-induced accumulation of cyclic AMP with IC50 of 2.58 μM in HeLa cells expressing ORL1 receptor.
Kinase Assay: A suspension of membranes from human μ-opioid receptor-expressing CHO-K1
cells in 50 mM Tris-HCl buffer (pH 7.4) containing 5 mM MgCl2 and 10% sucrose is incubated at room temperature for 2.5 h with 0.33 nM 3H-labeled
diprenorphine and various concentrations of JTC-801. The membranes are
collected by filtration using Whatman 934-AH, and radioactivity is
counted with a TopCount A9912V scintillation counter. Nonspecific
binding (6.4%) is determined with 10 μM naloxone. Specific binding is
calculated by subtracting nonspecific binding from the total binding.
Data are the mean±SE (n=3). |
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| In Vivo | Oral administration of JTC-801 (0.3-3 mg/kg) antagonizes nociceptin-induced allodynia in mice, and shows analgesic effect in a hot plate test using mice and in a formalin test using rats. In mouse hot-plate test, JTC-801 prolongs escape response latency (ERL) or exposed heat stimulus with minimum effective doses (MED) of 0.01 mg/kg by i.v. or 1 mg/kg by p.o. In the rat formalin test, JTC-801 reduces both the first and second phases of the nociceptive response with MED of 0.01 mg/kg71 by i.v. or 1 mg/kg by p.o. JTC-801 dose-dependently normalizes paw withdrawal latency (PWL). Although JTC-801 does not inhibit a chronic constriction injury (CCI)-induced decrease in bone mineral content (BMC) and bone mineral density (BMD), it inhibits an increase in the number of osteoclasts. Tactile allodynia induced by L5/L6 spinal nerve ligation is reversed by both systemic (3-30 mg/kg) and spinal (22.5 and 45 pg) JTC-801 in a dose-dependent manner. Furthermore, systemic JTC-801 reduces Fos-like immunoreactivity in the dorsal horn of the spinal cord (laminae I/II). JTC-801 produces dose-dependent mechanical and cold anti-allodynic effects with ED50 of 0.83 mg/kg and 1.02 mg/kg, respectively. |
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