The Role of Orexin-A in Water Intake in Water-deprived Rats

Background: The lateral hypothalamus (LH), which produces orexin, is vital for body solution homeostasis. Lateral hypothalamus (LH) lesion causes adipsia and its stimulation increases water intake. Objective: This study aimed to investigate the effect of an intracerebroventricular (ICV) injection of orexin-A (OXA) on water-drinking behavior in water-deprived rats. Metods: A total of 32 male Wistar rats (220–250 g) were used and divided into 4 groups, control (no injection), vehicle (Normal saline, 5 µL), OXA (30 µg/rat), SB-334867 (OXA receptor selective antagonist, 30 µg/rat). After the microinjection of drugs or vehicles in the right lateral ventricle, each rat was placed individually into the metabolic cage and the amount of water intake, the delay time for the first water intake, and the referral number for water intake were recorded for 4 h. Findings: This study showed that ICV administration of OXA increased both water intake and the referral number for water intake in water-deprived animals (P<0.05). On the other hand, ICV administration of SB-334867 decreased water intake compared to vehicle and control groups. Conclusion: It can be concluded that OXA has a regulatory role in water drinking behavior in water-depriving states.