Opiate disruption of maternal behavior: morphine reduces, and naloxone restores, c-fos activity in the medial preoptic area of lactating rats.
Morphine significantly impairs maternal behavior; naloxone, an opiate antagonist, restores it. Maternal behavior is associated with c-fos expression, an immediate early gene product, in the medial preoptic area (mPOA) of females. In two experiments, the effects of morphine-alone and morphine plus naloxone on the expression of c-fos were examined. On postpartum day 5, females were injected with morphine or saline (experiment 1), and morphine + naloxone or morphine + saline (experiment 2) and placed back in the home-cage, separated from their pups by a wire-mesh partition. A separate group in experiment 1 was injected but not exposed to pups. Processing for c-fos immunohistochemistry commenced, and c-fos positive cells in a proscribed portion of mPOA were counted. Morphine-treated females had fewer c-fos cells in mPOA compared to saline-treated females, and the presence of pups accounted for a significant increase in c-fos-expressing neurons, whereas in females not exposed to pups, morphine treatment did not significantly reduce baseline c-fos expression (experiment 1). Furthermore, naloxone mitigated the effect as morphine + naloxone-treated females expressed more c-fos cells compared to morphine + saline females (experiment 2). Morphine-treated females, therefore, may exhibit reductions in maternal behavior because of relative opiate-induced inactivation of areas of the brain devoted to the regulation of maternal behavior.
Stafisso-Sandoz
G
G
Department of Psychology, University of Richmond, VA 23173, USA.
Polley
D
D
Holt
E
E
Lambert
K G
KG
Kinsley
C H
CH
D000701:Analgesics, Opioid / Q000494:pharmacology*; D000818:Animals; D005260:Female; D007091:Image Processing, Computer-Assisted; D007774:Lactation / Q000187:drug effects; D008425:Maternal Behavior / Q000187:drug effects*; D009020:Morphine / Q000494:pharmacology*; D009270:Naloxone / Q000494:pharmacology*; D009292:Narcotic Antagonists / Q000494:pharmacology*; D009419:Nerve Tissue Proteins / Q000096:biosynthesis; D011301:Preoptic Area / Q000187:drug effects* / Q000378:metabolism; D016760:Proto-Oncogene Proteins c-fos / Q000096:biosynthesis; D051381:Rats; D017207:Rats, Sprague-Dawley
D000701:Analgesics, Opioid; D009292:Narcotic Antagonists; D009419:Nerve Tissue Proteins; D016760:Proto-Oncogene Proteins c-fos; D009270:Naloxone; D009020:Morphine