2.4 Intranucleus accumbens (NAc) infusions
Briefly, C57BL/6J mice were anaesthetized with 0.5% pentobarbital sodium solution (50 mg·kg-1, i.p.) and fixed in a stereotaxic apparatus (Kopf, Tujunga, CA), with the anaesthetizing effects evaluated by muscle relaxation, slow corneal reflex, and no skin pinch reaction. The scalp was cut, and the skull was exposed using 75% alcohol and 1% H2O2. The cannulas were implanted into the bilateral NAc according to bregma: anteroposterior, + 1.5mm; mediolateral, + 1.0mm; dorsoventral, - 4.5mm(B Jiang et al., 2013). The cannula was cemented in place, and the incision was sutured. The animals were allowed to recover for at least 5 days after surgery. Osmotic minipumps were designed to deliver bilateral microinjection of different amounts of D-serine (2ug/perside ;5ug/perside), K252a (5 ug/perside), fluoxetine (5 ug/perside), or saline (0.9%) into the NAc daily for 14 days. Each osmotic minipump was attached to a brain infusion cannula. A total volume of 1.0 uL was infused into each side over 15 min, and the injection syringe was maintained in place for an additional 5 minutes to limit reflux along the injection track. In some experiments, a nonspecific tyrosine kinase inhibitor, K252a (5ug/perside), was co-infused bilaterally with D-serine, K252a was infused bilaterally 20 minutes before infusion of D-serine.