title: Effects of acute ethanol on opioid peptide release in the central amygdala: an in vivo microdialysis study.
abstract: BACKGROUND
  There is experimental evidence that indicates that the endogenous opioid system of the central nucleus of the amygdala (CeA) may mediate some of the reinforcing effects of ethanol. However, the precise interactions of ethanol with the endogenous opioid system at the level of the CeA have not been investigated.
  
  
  OBJECTIVE
  The aim of the current study was to investigate the hypothesis that acute systemic ethanol administration will increase the release of endogenous opioid peptides at the level of the CeA in a time- and dose-dependent manner.
  
  
  METHODS
  Rats were implanted with a unilateral guide cannula to aim microdialysis probes at the CeA. Intraperitoneal injections of saline and various doses of ethanol (0.8, 1.6, 2.0, 2.4, and 2.8 g ethanol/kg body weight) were administered to the rats. Dialysate samples were collected at 30-min intervals at distinct time points prior to and following treatment. Radioimmunoassays specific for beta-endorphin, met-enkephalin, and dynorphin A1-8 were used to determine the effect of ethanol on the content of the opioid peptides in the dialysate.
  
  
  RESULTS
  We report that the 2.8-g/kg dose of ethanol induced a long-lasting increase in beta-endorphin release from 60 min onwards following administration and, later, an ongoing increase in dynorphin A1-8 release. None of the ethanol doses tested elicited significant changes in dialysate met-enkephalin content compared to the saline treatment.
  
  
  CONCLUSIONS
  Acute systemic ethanol administration induced a dose- and time-dependent increase in beta-endorphin and dynorphin A1-8 release at the level of the CeA, which may be involved in ethanol consumption.
authors.affiliation: Department of Physiology, McGill University, Montréal, Canada.
authors.forename: Minh P
authors.initials: MP
authors.lastname: Lam
authors.forename: Peter W
authors.initials: PW
authors.lastname: Marinelli
authors.forename: Li
authors.initials: L
authors.lastname: Bai
authors.forename: Christina
authors.initials: C
authors.lastname: Gianoulakis
mesh_terms: D000679:Amygdala / Q000737:chemistry / Q000187:drug effects* / Q000378:metabolism*; D000818:Animals; D004305:Dose-Response Relationship, Drug; D004399:Dynorphins / Q000378:metabolism; D004744:Enkephalin, Methionine / Q000378:metabolism; D000431:Ethanol / Q000008:administration & dosage / Q000097:blood / Q000494:pharmacology*; D007274:Injections, Intraperitoneal; D008297:Male; D017551:Microdialysis; D018847:Opioid Peptides / Q000737:chemistry / Q000187:drug effects* / Q000378:metabolism*; D010446:Peptide Fragments / Q000378:metabolism; D010455:Peptides / Q000378:metabolism; D010784:Photomicrography; D051381:Rats; D017207:Rats, Sprague-Dawley; D001615:beta-Endorphin / Q000378:metabolism
chemical_list: D018847:Opioid Peptides; D010446:Peptide Fragments; D010455:Peptides; D000431:Ethanol; D004744:Enkephalin, Methionine; D001615:beta-Endorphin; D004399:Dynorphins; C039666:dynorphin amide (1-10)