Stimuli Linked to Ethanol Availability Activate Hypothalamic CART and Orexin Neurons in a Reinstatement Model of Relapse

Background

There has been a recent upsurge of interest in the role of hypothalamic feeding peptides, in particular, orexin (hypocretin), in drug-seeking behavior. However, the potential role of other hypothalamic feeding peptides, such as cocaine- and amphetamine-regulated transcript (CART), in conditioned reinstatement has yet to be explored.

Methods

Animals were exposed to environmental stimuli previously associated with ethanol availability (EtOH S⁺), and sections from the hypothalamus and paraventricular thalamus (PVT), a recipient of CART and orexin innervation, were dual labeled for Fos-protein and either CART or orexin.

Results

Significantly larger numbers of Fos-positive arcuate nucleus CART and hypothalamic orexin neurons were seen in animals exposed to the EtOH S⁺ compared with nonreward S⁻ animals. Presentation of the EtOH S⁺ also increased numbers of Fos-positive PVT neurons. Fos-positive PVT neurons were observed to be closely associated with orexin and CART terminal fields.

Conclusions

Taken together, these findings suggest that activation of hypothalamic neuropeptide systems may be a common mechanism underlying drug-seeking behavior.