Effects of orexin-A on memory processing.

Orexin-A is an endogenous peptide with receptors present throughout the brain. Here, we examined the effect of post-training administration of orexin-A on retention in active and passive avoidance. Orexin-A administered by intracerebroventricular (i.c.v.) injection to CD-1 mice post-training improved retention in both T-maze footshock avoidance and one trial step-down passive avoidance. SAMP8 mice have age-related deficits in learning and memory, which correlate with an increase in brain levels of beta amyloid (Abeta) and an impaired response to memory-enhancing compounds. Orexin-A at 3nmol improved retention in young and old SAMP8 mice. These findings show that orexin-A can improve memory even with overproduction of Abeta.