Kappa-opioid receptor modulation of accumbal dopamine concentration during operant ethanol self-administration.
Our study examined ethanol self-administration and accumbal dopamine concentration during kappa-opioid receptor (KOPr) blockade. Long-Evans rats were trained to respond for 20 min of access to 10% ethanol (with sucrose) over 7 days. Rats were injected s.c. with the long-acting KOPr antagonist, nor-binaltorphimine (NOR-BNI; 0 or 20 mg/kg) 15-20 h prior to testing. Microdialysis revealed a transient elevation in dopamine concentration within 5 min of ethanol access in controls. NOR-BNI-treated rats did not exhibit this response, but showed a latent increase in dopamine concentration at the end of the access period. The rise in dopamine levels correlated positively with dialysate ethanol concentration but not in controls. NOR-BNI did not alter dopamine levels in rats self-administering 10% sucrose. The transient dopamine response during ethanol acquisition in controls is consistent with previous results that were attributed to ethanol stimulus cues. The altered dopamine response to NOR-BNI during ethanol drinking suggests that KOPr blockade temporarily uncovered a pharmacological stimulation of dopamine release by ethanol. Despite these neurochemical changes, NOR-BNI did not alter operant responding or ethanol intake, suggesting that the KOPr is not involved in ethanol-reinforced behavior under the limited conditions we studied.
Doyon
William M
WM
Department of Neuroscience, Baylor College of Medicine, Houston, TX 77030, USA.
Howard
Elaina C
EC
Shippenberg
Toni S
TS
Gonzales
Rueben A
RA
D019900:3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer / Q000494:pharmacology; D018712:Analgesics, Non-Narcotic / Q000494:pharmacology; D000818:Animals; D019540:Area Under Curve; D001522:Behavior, Animal; D002492:Central Nervous System Depressants / Q000008:administration & dosage*; D003216:Conditioning, Operant / Q000187:drug effects*; D004298:Dopamine / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D004327:Drinking Behavior / Q000187:drug effects; D004347:Drug Interactions; D000431:Ethanol / Q000008:administration & dosage*; D008297:Male; D017551:Microdialysis / Q000379:methods; D009271:Naltrexone / Q000031:analogs & derivatives / Q000494:pharmacology; D009292:Narcotic Antagonists / Q000494:pharmacology; D009714:Nucleus Accumbens / Q000378:metabolism*; D051381:Rats; D020318:Rats, Long-Evans; D017473:Receptors, Opioid, kappa / Q000502:physiology*; D012646:Self Administration / Q000379:methods
D018712:Analgesics, Non-Narcotic; D002492:Central Nervous System Depressants; D009292:Narcotic Antagonists; D017473:Receptors, Opioid, kappa; C051844:norbinaltorphimine; D000431:Ethanol; D009271:Naltrexone; D019900:3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; D004298:Dopamine