Enhanced sensitivity to naltrexone-induced drinking suppression of fluid intake and sucrose consumption in maternally separated rats.
Early-life stress has been identified as a risk factor in the development of a host of disorders, including substance abuse; however the link between early postnatal stress and changes in measures of reward has not been thoroughly researched. The current study had two main objectives: 1) to determine the impact of maternal separation (an animal model of early-life stress) on the consumption of 10% and 2.5% sucrose solutions by Long-Evans rat dams and male and female offspring, and 2) to determine the effect of the opioid antagonist naltrexone (0.1-3.0 mg/kg) on drinking by each of those groups. Dam-pup separations occurred for varying lengths of time during the first two postnatal weeks. In Experiment 1, a two-bottle choice test (sucrose solution vs. water) was administered across five days to both nonhandled (NH) and maternally-separated (MS) offspring as adults and to dams 2-4 weeks post-weaning. In Experiment 2, naltrexone was administered prior to two-bottle choice tests. MS males and the dams of MS litters exhibited increased intake of total fluid and sucrose solutions, whereas results from females were less consistent. Naltrexone elicited a greater decrease in fluid intake and sucrose intake in male MS offspring compared to male NH offspring. These results indicate that early postnatal stress alters both sucrose consumption, a non-drug measure of reward, and apparently the brain opioid systems that mediate naltrexone-induced drinking suppression.
Michaels
Clifford C
CC
Department of Pharmacology, Emory University School of Medicine, Atlanta, GA 30322, USA. ccmicha@emory.edu
Holtzman
Stephen G
SG
D000818:Animals; D001921:Brain / Q000187:drug effects / Q000503:physiopathology; D004326:Drinking / Q000187:drug effects* / Q000502:physiology; D005260:Female; D005518:Food Preferences / Q000187:drug effects / Q000502:physiology; D008297:Male; D023421:Models, Animal; D009271:Naltrexone / Q000494:pharmacology*; D009292:Narcotic Antagonists / Q000494:pharmacology; D018847:Opioid Peptides / Q000502:physiology; D011247:Pregnancy; D051381:Rats; D020318:Rats, Long-Evans; D012201:Reward; D012727:Sex Characteristics; D012996:Solutions; D013315:Stress, Psychological / Q000150:complications / Q000503:physiopathology; D019966:Substance-Related Disorders / Q000209:etiology / Q000503:physiopathology / Q000523:psychology; D013395:Sucrose / Q000008:administration & dosage
D009292:Narcotic Antagonists; D018847:Opioid Peptides; D012996:Solutions; D013395:Sucrose; D009271:Naltrexone