Ascending orexinergic pathways and alcohol-seeking.

Orexin (hypocretin) containing neurons reside in discrete regions of the lateral hypothalamus from where they innervate the entire neuroaxis. Via actions upon orexin receptors (OX1 and OX2), the orexin peptides (orexin A and orexin B) are thought to play a role in ethanol consumption and seeking. While a role for OX1 receptors in these behaviours is established, the case for OX2 receptors is less clear at present, although recent data certainly support an involvement of OX2 receptors in ethanol consumption. In terms of circuitry, orexin receptors the ventral tegmental area appear to contribute to ethanol consumption. Other loci remain to be characterised, and we suggest prefrontal cortical orexin receptors deserve attention in this respect.