Recovery profiles from reward downshift are correlated with operant licking maintained by alcohol, but not with genetic variation in the mu opioid receptor.
After ten 5-min sessions of access to 32% sucrose, a reward downshift (RD) to 2% sucrose induces a transient rejection of the reward. Animals were segregated according to the speed of recovery from RD into Fast-recovery and Slow-recovery subgroups. Animals were subsequently trained in an operant licking (OL) task in which licking at an empty tube provided 10 s of access to a second tube containing 66% alcohol. Licking on the first tube was subjected to a progressive ratio (PR) schedule with a step of 4 licks. Fast-recovery animals (both males and females) licked to a higher ratio than Slow-recovery animals. Animals were also exposed to a well-lit open field (OF) for 20 min. Fast- and Slow-recovery males and females exhibited equal levels of activity in the OF. Tissue samples from tails were assessed for two well-known allelic variations of the human opioid receptor gene, OPRM1, known to affect mu opioid sensitivity: The C17T and A118G single nucleotide polymorphisms. There was no evidence of a relationship between genotype and behavior, suggesting that these genetic mechanisms in humans do not account for the individual differences in recovery from RD and OL for alcohol in rats.
['Thompson|Joanna B|JB|', 'Daniel|Alan M|AM|', 'Rushing|Brenda G|BG|', 'Papini|Mauricio R|MR|']
D000818:Animals D000431:Ethanol D005260:Female D005838:Genotype D020641:Polymorphism, Single Nucleotide D051381:Rats D017450:Receptors, Opioid, mu D012201:Reward
Reward downshift OPRM1 A118G single nucleotide polymorphism Alcohol intake C17T single nucleotide polymorphism Open field activity