The dual orexin/hypocretin receptor antagonist, almorexant, in the ventral tegmental area attenuates ethanol self-administration

PLoS One. 2012;7(9):e44726. doi: 10.1371/journal.pone.0044726. Epub 2012 Sep 21.

Abstract

Recent studies have implicated the hypocretin/orexinergic system in reward-seeking behavior. Almorexant, a dual orexin/hypocretin R(1) and R(2) receptor antagonist, has proven effective in preclinical studies in promoting sleep in animal models and was in Phase III clinical trials for sleep disorders. The present study combines behavioral assays with in vitro biochemical and electrophysiological techniques to elucidate the role of almorexant in ethanol and sucrose intake. Using an operant self-administration paradigm, we demonstrate that systemic administration of almorexant decreased operant self-administration of both 20% ethanol and 5% sucrose. We further demonstrate that intra-ventral tegmental area (VTA) infusions, but not intra-substantia nigra infusions, of almorexant reduced ethanol self-administration. Extracellular recordings performed in VTA neurons revealed that orexin-A increased firing and this enhancement of firing was blocked by almorexant. The results demonstrate that orexin/hypocretin receptors in distinct brain regions regulate ethanol and sucrose mediated behaviors.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Acetamides / pharmacology*
  • Animals
  • Electrophysiology
  • Ethanol / metabolism*
  • Isoquinolines / pharmacology*
  • Male
  • Motor Activity / drug effects
  • Orexin Receptors
  • Rats
  • Receptors, G-Protein-Coupled / antagonists & inhibitors*
  • Receptors, Neuropeptide / antagonists & inhibitors*
  • Sucrose / metabolism*
  • Ventral Tegmental Area / drug effects*
  • Ventral Tegmental Area / metabolism*

Substances

  • Acetamides
  • Isoquinolines
  • Orexin Receptors
  • Receptors, G-Protein-Coupled
  • Receptors, Neuropeptide
  • Ethanol
  • Sucrose
  • almorexant

Grants and funding

The research was carried out with the help of Department of Defense, TATRC grant W81XWH-10-1-0247 (www.tatrc.org) awarded to S.E.B. and A.B. and the state funding for medical research through UCSF to S.E.B. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.