NMDA- and 6-OHDA-induced Lesions in the Nucleus Accumbens Differently Affect Maternal and Infanticidal Behavior in Pup-naïve Female and Male Mice.

Virgin and pups-naïve female and male adult mice display two opposite responses when they are exposed to pups for the first time. While females generally take care of the pups, males attack them. Since the nucleus accumbens (NA), and its dopaminergic modulation, is critical in integrating information and processing reward and aversion, we investigated if NMDA- and 6-OHDA-induced lesions, damaging mostly NA output and dopaminergic inputs respectively, affected female maternal behavior (MB) or male infanticidal behavior (IB) in mice.

NMDA lesions in the prefrontal cortex delay the onset of maternal, but not infanticidal behavior in pup-naïve adult mice (C57BL/6).

While most pup-naïve adult female mice can display, or be induced (by repeated exposure to pups) to display parental behavior rapidly, adult males are infanticidal or nonparental. The medial prefrontal cortex (mPFC) participates in attentional selection, decision-making, behavioral flexibility, and planning that may be critical in the rapid display of parental or infanticidal behavior. We investigated if NMDA-induced lesions in the mPFC (targeting prelimbic cortex) inhibited maternal or infanticidal behavior in pup-naïve adult female and male mice (C57BL/6), respectively.

Prefrontal cortex is associated with the rapid onset of parental behavior in inexperienced adult mice (C57BL/6).

There is significant variability in the immediate behavioral response displayed by inexperienced adult mice when exposed to pups for the first time. The aim of this study was to determine which brain regions were engaged (higher c-Fos-immunoreactivity, c-Fos-ir) when virgin females, that were exposed to pups for 15 or 60 min, displayed full parental behavior (FPB), partial parental behavior (PPB), or non-parental behavior (NPB), or virgin males displayed PPB or infanticidal behavior (IB). The number of c-Fos-ir neurons in the prelimbic cortex (PL) was higher in parental females than in the NPB group (after a 15-min exposure), and the group not exposed to pups (NE).

Are age and sex differences in brain oxytocin receptors related to maternal and infanticidal behavior in naïve mice?

This article is part of a Special Issue "Parental Care". There is significant variability in the behavioral responses displayed by naïve young and adult mice when first exposed to pups. This variability has been associated with differences in the expression of oxytocin receptors (OXTRs) in the brain in several species.

Development and expression of maternal behavior in naïve female C57BL/6 mice.

Naïve female mice are usually described as spontaneously maternal. We investigated how many exposures to pups (15 min vs. 1 hr) were needed to induce full maternal behavior (FMB) in 20-22, 30-35, 60-65-days-old naïve female mice (C57BL/6), and how cohabitation with the parturient mother and newborn siblings facilitated juvenile maternal behavior (MB).