Effects of chronic and intermittent cocaine treatment on dominance, aggression, and oxytocin levels in post-lactational rats.
BACKGROUND
Little is known about mechanisms underlying female rodent aggression during the late postpartum period with no pups present. Studies of aggression, dominance, and oxytocin (OT) response in cocaine-treated females are sparse.


OBJECTIVE
This study was designed to examine dominance (drinking success) and aggression in a limited-access drinking model of water competition. Acute OT level measures were made on postpartum day (PPD) 36 in several brain regions of interest. Chronic and intermittent cocaine- and saline-treated and untreated rats 10 days post-weaning were tested (without pups) over PPDs 31-35 following cessation of cocaine treatment 10-30 days before testing.


METHODS
Subjects were water-deprived overnight, and triads consisting of an untreated control (UN), a chronic continuous saline-treated (CS), and chronic continuous cocaine-treated (CC; 30 mg/kg/day throughout gestation) or a UN, an intermittent saline-treated (IS), and an intermittent cocaine-treated (IC; 30 mg/kg two consecutive days every 4 days throughout gestation until PPD 20) female were tested for aggression and drinking behavior during 5 min sessions on five consecutive days. The amygdala, medial preoptic area (MPOA), and ventral tegmental area were assayed for OT levels.


RESULTS
CC and IC females were more aggressive than controls, but only IC females drank more often than controls. OT levels were lower in the MPOA of IC and CC females than in controls.


CONCLUSIONS
Findings demonstrate that long after cessation of treatment, CC- and IC-treated non-lactating females (no pups present) had higher rates of aggression, altered drinking behavior, and acutely lower MPOA OT levels.
Department of Psychiatry, University of North Carolina, 430 Taylor Hall, CB# 7096, Chapel Hill, NC 27599, USA. jjohns@med.unc.edu
Josephine M
JM
Johns
Matthew S
MS
McMurray
Paul W
PW
Joyner
Thomas M
TM
Jarrett
Sarah K
SK
Williams
Elizabeth T
ET
Cox
Mitchell A
MA
Black
Christopher L
CL
Middleton
Cheryl H
CH
Walker
D000374:Aggression / Q000187:drug effects*; D000679:Amygdala / Q000378:metabolism; D000818:Animals; D003042:Cocaine / Q000008:administration & dosage / Q000633:toxicity*; D003163:Competitive Behavior / Q000187:drug effects; D004326:Drinking; D004334:Drug Administration Schedule; D005260:Female; D010121:Oxytocin / Q000187:drug effects* / Q000378:metabolism; D049590:Postpartum Period; D011301:Preoptic Area / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D012930:Social Dominance; D013997:Time Factors; D017557:Ventral Tegmental Area / Q000378:metabolism
D010121:Oxytocin; D003042:Cocaine