Duloxetine

Five drugs were tested in this study: duloxetine, celecoxib (Tokyo Chemical Industry Co., Ltd, Tokyo, Japan), pregabalin (ChemFaces, Hubei, China), venlafaxine, and tramadol (Sigma-Aldrich, St. Louis, MO, USA). All drugs were dissolved in distilled water (Otsuka Pharmaceutical Factory Inc, Tokushima, Japan) containing 0.5% w/v methylcellulose 400 solution (Fujifilm Wako Pure Chemical Corporation, Osaka, Japan) and administered orally (5 mL/kg) on Day 7 after SNL.

Duloxetine (3, 10, 30 mg/mL/kg, Tokyo Chemical Industry Co., Ltd., Tokyo, Japan) was dissolved in 50% dimethylsulfoxide and saline (vehicle), and injected intraperitoneally (Ito et al., 2018 (link), Hiroki et al., 2017 (link), Sun et al., 2014 (link)). Idazoxan hydrochloride (α2 adrenoceptor antagonist, Sigma Aldrich, St. Louis, MO, USA) and atropine (muscarinic antagonist, Sigma Aldrich) were dissolved in saline. One hundred and sixty-five minutes following intraperitoneal Duloxetine injection, 10 µL idazoxan (30 µg/10 µL) (Hayashida et al., 2008a (link)) or atropine (30 µg/10 µL) (Hayashida et al., 2007 (link)) was administered to the rats through an intrathecal catheter, and this was followed by flushing with 10 µL of saline. 7,8-Dihydroxyflavone (7,8-DHF, TrkB agonist, Wako Pure Chemical Industries, Ltd., Osaka, Japan), dissolved in 0.1 mol/L PBS containing 20% dimethylsulfoxide. 7,8-DHF (5 mg/mL/kg/day) (Kato et al., 2019 (link), Andero et al., 2012 (link)), was injected intraperitoneally for 5 days from week 6 (day 42) to week 7 (day 46) following SNL surgery.