title: Separation stress, litter size, and the rewarding effects of low-dose morphine in the dams of maternally separated rats.
abstract: Potential differences in sensitivity to the rewarding effects of morphine as a function of litter separation stress were assessed in post-weaning rat dams. During the first two weeks postnatal, Sprague-Dawley rat litters were subjected to daily 15- or 180-min sessions of dam-pup separation while control litters only experienced twice-weekly animal facility care. One week after weaning, the dams (n=7 per group) underwent a fully unbiased conditioned place preference (CPP) procedure to 1 mg/kg subcutaneous morphine. CPP responses after each conditioning cycle were recorded. Rates of acquisition and asymptotic levels of CPP were comparable in all groups; however, an inverse relationship between litter size and magnitude of morphine CPP was revealed. Although these initial data indicate no differential sensitivity to the rewarding effects of low-dose morphine produced by the stress of litter separation, this assessment of litter size and drug-induced place conditioning in post-weaning litter-separated dams is the first of its kind. Potential effects of other doses, drugs of abuse and post-partum manipulations remain to be evaluated within this emerging etiological model.
authors.affiliation: Psychopharmacology Laboratory, Department of Psychology, American University, 4400 Massachusetts Avenue, NW, Washington, DC 20016, USA. PeteRoma@gmail.com
authors.forename: Peter G
authors.initials: PG
authors.lastname: Roma
authors.forename: Mary E
authors.initials: ME
authors.lastname: Huntsberry
authors.forename: Anthony L
authors.initials: AL
authors.lastname: Riley
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D000831:Animals, Newborn; D001522:Behavior, Animal / Q000187:drug effects; D049628:Body Size / Q000187:drug effects*; D003216:Conditioning, Operant / Q000187:drug effects; D005260:Female; D066298:In Vitro Techniques; D008426:Maternal Deprivation; D009020:Morphine / Q000008:administration & dosage*; D009294:Narcotics / Q000008:administration & dosage*; D011247:Pregnancy; D051381:Rats; D012201:Reward; D013315:Stress, Psychological / Q000188:drug therapy*
chemical_list: D009294:Narcotics; D009020:Morphine