Social and Appetitive Behavior in the Social Transmission of Food Preference Paradigm Predict Activation of Orexin-A producing Neurons

Orexin-producing cells in the lateral hypothalamic area have been shown to be involved in a wide variety of behavioral and cognitive functions, including the recall of appetitive associations and a variety of social behaviors. Here, we investigated the role of orexin in the acquisition and recall of socially transmitted food preferences in the rat. Rats were euthanized following either acquisition, short-term recall, or long-term recall of a socially transmitted food preference and their brains processed for orexin and c-Fos expression. We found that while there were no significant differences in c-Fos expression between control and experimental subjects at any of the tested timepoints, females displayed significantly more activity in both orexinergic and non-orexinergic cells in the lateral hypothalamus. Moreover, both social and appetitive behavior were significantly predictive of the activation of orexinergic neurons with sex serving as an important mediating factor in both cases. Additionally, we found that social behavior was significantly predictive of c-Fos expression in the infralimbic cortex. Finally, our data showed that orexin activity during the dark cycle negatively correlated with the total amount of food eaten prior to euthanasia in male but not female rats, a finding that contradicts the standard perception of orexin as an appetite stimulant. These findings provide evidence for a role of the orexin system in generalized social and appetitive behavior, as well as a potential sex-specific role for the orexin system in balancing the stimulation of feeding behavior with the sleep/wake cycle.