2.6. In vivo microdialysis in the rat nucleus accumbens

Anesthetized rats (chloral hydrate 400 mg/kg, i.p.) were positioned in a Kopf stereotaxic frame. A guide cannula (CMA/12 microdialysis probe, Phymep) was implanted into the nucleus accumbens (anterior‐posterior, +1.2 mm from bregma; medial‐lateral, +0.18 mm; dorsal‐ventral, −5.8 mm from dura) according to the atlas of Paxinos and Watson.30 It was secured with dental cement and anchor screws into the skull. Rats were single‐housed for postoperative recovery for at least 5 days. Then, microdialysis experiments were performed as described previously25 by use of a CMA/12 microdialysis probe (2‐mm length) to measure the effects on extracellular DA of vehicle (methylcellulose 1% in water, 5 ml/kg, p.o.), or solriamfetol (30 and 100 mg/kg, p.o.).

Male OF1 mice (22–25 g) were fasted for 16 h before p.o. administration of vehicle (methylcellulose 1% in water, 10 ml/kg, p.o.) or of solriamfetol (30 and 100 mg/kg, p.o.). Ninety minutes after the treatments, animals were killed. The brain was dissected out and homogenized in 10 volumes (w/v) of ice‐cold 0.4 N perchloric acid. The clear supernatant that was obtained after centrifugation (2000 g for 30 min at 4℃) was stored at −20℃ before the level of tele‐methylhistamine was measured by enzyme immunoassay as described previously.31