Role of Leptin and Orexin-A Within the Suprachiasmatic Nucleus on Anxiety-Like Behaviors in Hamsters

It is well established that the maintenance of energy expenditure is linked to active hypothalamic neural mechanisms controlling adaptive stimuli such as food intake. Variations of glucose levels and hormonal (leptin plus orexin-A) parameters, which are involved with energy homeostasis during different behavioral states, have not yet been fully defined. In this first study, behavioral analyses of an unpredictable stress model dealing with the actions of a sub-chronic administration of orexin-A (ORX-A) and the anti-hunger neuropeptide, i.e., leptin (LEP) within the hypothalamic suprachiasmatic (SCH) nucleus, were conducted on the valuable hibernating rodent (hamster; Mesocricetus auratus) model noted for its distinct depression and anxiety states. Treatment with LEP accounted for a notable reduction (p < 0.01) of body weight in stressed hamsters that not only executed very evident (p < 0.001) movements to and from elevated plus maze (EPM) but also spent less time in the dark area of the light–dark box test (LDT). Conversely, ORX-A predominantly evoked anxiogenic effects that were inverted by LEP. Interestingly, the anti-hunger neuropeptide accounted for both down-regulated NPY1 transcripts in mostly lateral-posterior hypothalamic areas while up-regulated levels were detected in the parietal cerebral cortex, hippocampus, and amygdala, which largely behaved in an opposite manner to ORX-A-dependent effects. Overall, the present findings corroborate a predominating LEPergic effect of the SCH toward the reduction of hamster anxiety-like behaviors with respect to that of ORX-A signaling, which may constitute useful therapeutic targets for stress-related obesity states.