title: Effect of acute ethanol administration on the release of opioid peptides from the midbrain including the ventral tegmental area.
abstract: BACKGROUND
  Experimental evidence suggests that ethanol alters the activity of the endogenous opioid peptide systems in a dose and brain-region dependent manner. These alterations may influence the processes of ethanol reward and reinforcement. Thus, it was the objective of this study to investigate the response of the 3 major opioid peptide systems (endorphins, enkephalins, and dynorphins) to acute ethanol administration, at the level of the midbrain including the ventral tegmental area (midbrain/VTA), a region important for drug, including ethanol reinforcement.
  
  
  METHODS
  Using the in vivo microdialysis technique coupled with specific solid-phase radioimmunoassay for beta-endorphin, met-enkephalin, and dynorphin A(1-8,) changes in the extracellular concentration of theses peptides at the level of midbrain/VTA were determined at distinct time points following the administration of 0.0 (saline), 0.8, 1.2, 1.6, 2.0, and 2.4 g ethanol/kg B.Wt.
  
  
  RESULTS
  A biphasic effect of ethanol on beta-endorphin release was found, with low to medium (1.2, 1.6, and 2.0 g) but not high (2.4 g) doses of ethanol, inducing a significant increase in the dialysate content of beta-endorphin. A late increase in the dialysate content of dynorphin A(1-8) was observed in response to the 1.2 g ethanol dose. However, none of the ethanol doses tested significantly altered the content of met-enkephalin in the dialysate.
  
  
  CONCLUSIONS
  The present findings suggest that the ethanol-induced increase of beta-endorphin release at the level of midbrain/VTA may influence alcohol reinforcement.
authors.affiliation: Department of Psychiatry, McGill University, Montréal, Québec, Canada.
authors.forename: Samuel
authors.initials: S
authors.lastname: Jarjour
authors.forename: Li
authors.initials: L
authors.lastname: Bai
authors.forename: Christina
authors.initials: C
authors.lastname: Gianoulakis
mesh_terms: D000437:Alcoholism / Q000378:metabolism; D000818:Animals; D002492:Central Nervous System Depressants / Q000097:blood / Q000494:pharmacology*; D004195:Disease Models, Animal; D004305:Dose-Response Relationship, Drug; D004399:Dynorphins / Q000378:metabolism; D004744:Enkephalin, Methionine / Q000378:metabolism; D000431:Ethanol / Q000097:blood / Q000494:pharmacology*; D007274:Injections, Intraperitoneal; D008297:Male; D008636:Mesencephalon / Q000187:drug effects* / Q000378:metabolism*; D018847:Opioid Peptides / Q000378:metabolism*; D010446:Peptide Fragments / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D013997:Time Factors; D017557:Ventral Tegmental Area / Q000187:drug effects* / Q000378:metabolism*; D001615:beta-Endorphin / Q000378:metabolism
chemical_list: D002492:Central Nervous System Depressants; D018847:Opioid Peptides; D010446:Peptide Fragments; D000431:Ethanol; D004744:Enkephalin, Methionine; D001615:beta-Endorphin; D004399:Dynorphins; C026770:dynorphin (1-8)