Selective actions of central mu and kappa opioid antagonists upon sucrose intake in sham-fed rats.
Intake of a palatable sucrose solution in real-fed rats is mediated in part by central mu and kappa opioid receptors. Since general opioid antagonists still inhibit sucrose intake in sham-fed rats, the present study examined whether centrally administered mu (beta-funaltrexamine: 5, 20 micrograms), mu1 (naloxonazine: 50 micrograms), kappa (nor-binaltorphamine: 1, 5, 20 micrograms), delta (naltrindole: 20 micrograms) or delta 1 (DALCE: 40 micrograms) opioid subtype antagonists altered sucrose intake in sham-fed rats in a similar manner to systemic naltrexone (0.01-1 mg/kg) and whether such effects were equivalent to altering the sucrose concentration. Sucrose (20%) intake in sham-fed rats was significantly and dose-dependently reduced by naltrexone (59%), beta-funaltrexamine (44%) and nor-binaltorphamine (62%), but not by naloxonazine, naltrindole or DALCE. The reductions in sham sucrose (20%) intake by general, mu and kappa antagonism were similar in pattern and magnitude to diluting sucrose concentration from 20% to 10% in untreated sham-fed rats. Since both real-fed and sham-fed rats share similar patterns of specificity of opioid effects, magnitudes and potencies of inhibition, it suggests that central mu and kappa antagonism acts on orosensory mechanisms supporting sucrose intake.
Leventhal
L
L
Department of Psychology, Queens College, City University of New York, Flushing 11367, USA.
Kirkham
T C
TC
Cole
J L
JL
Bodnar
R J
RJ
D000818:Animals; D002552:Cerebral Ventricles; D004435:Eating / Q000502:physiology*; D016308:Enkephalin, Leucine-2-Alanine / Q000031:analogs & derivatives / Q000494:pharmacology; D007263:Infusions, Parenteral; D008297:Male; D009270:Naloxone / Q000031:analogs & derivatives / Q000494:pharmacology; D009271:Naltrexone / Q000031:analogs & derivatives / Q000494:pharmacology; D009292:Narcotic Antagonists / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D017473:Receptors, Opioid, kappa / Q000037:antagonists & inhibitors*; D017450:Receptors, Opioid, mu / Q000037:antagonists & inhibitors*; D013395:Sucrose / Q000378:metabolism*
D009292:Narcotic Antagonists; D017473:Receptors, Opioid, kappa; D017450:Receptors, Opioid, mu; C053821:enkephalin-Leu, Ala(2)-Cys(6)-; D009270:Naloxone; C051844:norbinaltorphimine; D013395:Sucrose; D009271:Naltrexone; D016308:Enkephalin, Leucine-2-Alanine; C024524:beta-funaltrexamine; C034643:naloxonazine; C055382:naltrindole