Reinforcing properties of ethanol in neonatal rats: involvement of the opioid system.
Toward understanding why infant rats ingest high levels of ethanol without initiation procedures, the authors tested effects of mu and kappa receptor antagonists on ethanol reinforcement in neonatal rats. After an intracisternal injection of CTOP (micro antagonist), nor-Binaltorphimine (kappa antagonist), or saline, newborn (3-hr-old) rats were given conditioning pairings of an odor with intraorally infused ethanol or a surrogate nipple with ethanol administered intraperitoneally (to minimize ethanol's gustatory attributes). In each case, these opioid antagonists reduced or eliminated ethanol's reinforcement effect. The same effects occurred with saccharin as the reinforcer in olfactory conditioning. The results imply that activation of mu and kappa receptors, apparently acting jointly, is necessary for reinforcement or that antagonists of this activity impair basic conditioning.
Nizhnikov
Michael E
ME
Center for Developmental Psychobiology, Department of Psychology, Binghamton University, State University of New York, Binghamton, NY 139002-6000, USA. bh08588@binghamton.edu
Varlinskaya
Elena I
EI
Petrov
Evgeniy S
ES
Spear
Norman E
NE
D000704:Analysis of Variance; D000818:Animals; D000831:Animals, Newborn; D001522:Behavior, Animal / Q000187:drug effects / Q000502:physiology; D001835:Body Weight / Q000187:drug effects; D001903:Bottle Feeding / Q000379:methods; D002492:Central Nervous System Depressants / Q000008:administration & dosage*; D002585:Cesarean Section / Q000379:methods; D003214:Conditioning, Classical / Q000187:drug effects*; D000431:Ethanol / Q000008:administration & dosage*; D005260:Female; D008297:Male; D009271:Naltrexone / Q000031:analogs & derivatives / Q000494:pharmacology; D009292:Narcotic Antagonists / Q000494:pharmacology; D009294:Narcotics / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012054:Reinforcement, Psychology; D012737:Sex Factors; D013004:Somatostatin / Q000031:analogs & derivatives / Q000494:pharmacology
D002492:Central Nervous System Depressants; D009292:Narcotic Antagonists; D009294:Narcotics; C049352:phenylalanyl-cyclo(cysteinyltyrosyl-tryptophyl-ornithyl-threonyl-penicillamine)threoninamide; C051844:norbinaltorphimine; D000431:Ethanol; D013004:Somatostatin; D009271:Naltrexone