Orexin-A microinjection mediated food and water intake are antagonized by selective orexin-1 receptor antagonist in the bed nucleus of stria terminalis

Orexins are expressed by lateral hypothalamic neurons which project to numerous brain regions such as the cortex, hypothalamus, brainstem and the limbic system including the amygdala (AMY) and the bed nucleus of stria terminalis (BST). Orexinergic system coordinates the metabolic, motivational, motor, autonomic and arousal processes necessary to elicit environmentally appropriate behaviors. In our previous experiments, orexin-A (OXA) microinjections into the BST evoked dose-dependent increase of liquid food and water intake. Since in the BST high level of orexin-1 receptor (OX1R) mRNA was observed, in the present experiments the effect of selective OX1R antagonist SB334867 was examined in male Wistar rats. One hundred ng (0.26 nmol) SB334867 was microinjected bilaterally alone or 15 min prior 500 ng (0.14 nmol) OXA bilateral microinjections to prove whether the effects of OXA on liquid food and water intake can be antagonized. OXA significantly enhanced liquid food consumption and water intake, and these effects could be antagonized by SB334867. Application of the antagonist SB334867 alone did not modify intakes. Our results show that OXA induced enhancement on liquid food ingestion and water intake can be antagonized by SB334867 indicating that these effects are mediated by OX1Rs in the BST.