Incentive salience of cocaine across the postpartum period of the female rat.
RATIONALE-OBJECTIVES: Our prior conditioned place preference (CPP) work demonstrates that late (day16) postpartum female rats consistently prefer cocaine- over pup-associated chambers, whereas far fewer early postpartum (day8) females prefer the cocaine-associated chamber. The present study examines early and late postpartum females' preference for a cocaine-associated chamber when contrasted with a chamber associated with saline (rather than pups).


METHODS
Postpartum females were tested for conditioned preference for chambers associated with cocaine (10 mg/kg subcutaneous (SC) or 0.5, 5, 10, or 20 mg/kg intraperitoneal (IP) injections) versus saline; preferences of virgin female and male rats for select cocaine stimuli (10mg/kg SC or IP) were also tested. Locomotion was recorded during CPP conditioning and testing.


RESULTS
Early and late postpartum females expressed strikingly similar preference for the cocaine-associated chamber across all administration routes and doses. IP cocaine produced an orderly, inverted U-shaped dose-preference curve, with preference peaking at the 5 mg/kg dose (83% of females). While many postpartum females preferred 10mg/kg cocaine administered either SC or IP, both virgin females and males expressed strong aversion to SC cocaine and, while virgin females strongly preferred IP cocaine, males remained relatively indifferent. Across 10mg/kg IP cocaine-conditioning sessions, locomotor sensitization occurred exclusively in cocaine- but not saline-preferring postpartum females. Locomotor rate was lower in preferred versus nonpreferred chambers at CPP test.


CONCLUSIONS
Early and late postpartum females may be equally and uniquely susceptible to sampling and/or abuse of modestly salient doses of cocaine (10mg/kg SC; 5mg/kg IP) compared to virgin females and/or males.
Seip
Katharine M
KM
Center for Molecular and Behavioral Neuroscience, Rutgers University, 197 University Avenue, Newark, NJ 07102, USA. kseip@pegasus.rutgers.edu
Pereira
Mariana
M
Wansaw
Michael P
MP
Reiss
Jenny I
JI
Dziopa
Eugenia I
EI
Morrell
Joan I
JI
D000818:Animals; D002755:Choice Behavior / Q000187:drug effects*; D003042:Cocaine / Q000008:administration & dosage*; D003214:Conditioning, Classical; D004305:Dose-Response Relationship, Drug; D005260:Female; D007274:Injections, Intraperitoneal; D007279:Injections, Subcutaneous; D008297:Male; D008425:Maternal Behavior / Q000187:drug effects; D009042:Motivation; D009043:Motor Activity / Q000187:drug effects; D011247:Pregnancy; D011270:Pregnancy, Animal; D051381:Rats; D017207:Rats, Sprague-Dawley; D012737:Sex Factors; D012931:Social Environment
D003042:Cocaine