SNAP: Female mice received an s.c. injection with 8 mg/kg SNAP (Sigma-Aldrich; N3398) diluted in 100 µL saline 15 min before behavioral testing, and the chosen dose was based on previous reports (24 (link)). Kisspeptin: Female mice received an s.c. injection with 0.52 µg/kg kisspeptin-10 (Kiss-10; rodent metastin [45 (link)54 (link, link, link, link, link, link, no link found, link, no link found)] amide; GeneCust YY-10-NH2) diluted in 100 µL saline 30 min before the behavioral test based on previous reports (24 (link)). sildenafil citrate: Female mice received an i.p. injection with 15 mg/kg sildenafil citrate (Sigma-Aldrich; 171599–83-0) 1 h before behavioral assessment based on previous trials from our laboratory. sildenafil citrate was first diluted in DMSO to make up a stock solution of 25 mg/mL and further diluted with sterile saline to make up a working solution of 15 mg/mL for s.c. injection on the day of the injection.