Puerperal and parental experiences alter rat preferences for pup odors via changes in the
oxytocin system |
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| Authors: | Arisa MUNETOMO Hirotaka ISHII Takenori MIYAMOTO Yasuo SAKUMA Yasuhiko KONDO |
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| Institution: | 1)Laboratory of Behavior Neuroscience, Faculty of Science, Japan Women’s University, Tokyo 112-8681, Japan;2)Department of Physiology, Graduate School of Medicine, Nippon Medical School, Tokyo 113-8602, Japan;3)Department of Animal Sciences, Teikyo University of Science, Tokyo 120-0045, Japan |
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| Abstract: | In the rat, induction of maternal behavior depends on the parity of the female. For example, nulliparous
(NP) females need longer exposure to pups than multiparous (MP) or lactating (L) females to exhibit similar
maternal behavior. In this study, we investigated the role of brain oxytocin in the approaching behavior of
these female rats. Olfactory preferences for pup odors were examined for 8 consecutive days. Each preference
test was followed by direct overnight exposure to pups. On the 8th day, MP and L, but not NP females showed
robust pup-odor preferences. After the behavioral test, half of the females were exposed to pups for 2 h,
whereas the other half were not. The females were then sacrificed to analyze brain oxytocin (OXT) and
vasopressin (AVP) activities by cFos immunohistochemistry and to quantify their receptor mRNA expression using
real-time PCR. In the paraventricular nucleus (PVN), the percentage of cFos-positive OXT neurons was
significantly larger in MP and L females than in NP females after pup exposure. No significant differences
were found in cFos expression in OXT neurons of the supraoptic nucleus (SON) or in AVP neurons of either the
PVN or SON. Expression of OXT receptor mRNA in the medial preoptic area and amygdala of the control groups was
also higher in MP females than in NP females. Finally, we demonstrated that infusion of OXT into the lateral
ventricle of NP females promoted preferences for pup odors. These results indicate that puerperal and parental
experiences enhance the responsiveness of OXT neurons in the PVN to pup stimuli and establish olfactory
preferences for these odors in a parity-dependent manner. |
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| Keywords: | Maternal behavior Olfactory preference Oxytocin Paraventricular nucleus Supraoptic nucleus Vasopressin |
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