Activity of the oxytocinergic nuclei in the maternal brain

Abstract

In several mammals and nonmammalian species, oxytocin (OT) has been shown to play a crucial role in the control of social interactions including maternal behaviours. Maternal care is especially important, since it facilitates not just nurturing and thermoregulation of the offspring, but also an appropriate neurodevelopment that promotes physical and mental health of the infants throughout their life. That’s why we are studying maternal behaviours. We use mice, which have become a good model for research of the neurobiology of maternal care and its disorders, because they show a neuroendocrinological control of maternal behaviour similar to humans. Maternal behaviour is controlled by the socio-sexual brain network (SBN), which is targeted by projections of oxytocinergic (among others) cells located in the bed nucleus of the stria terminalis (BSTMPM), the preoptic area (the so-called AC/ADP region) and the paraventricular (Pa) and supraoptic hypothalamic nuclei (SON). That way, oxytocin modulates SBN activity during motherhood to facilitate maternal care of pups. Therefore, we analysed the immunoreactivity for oxytocin and for c-FOS (a good marker for neuronal activity) in these brain centres of dams and pup-sensitized virgin female mice (godmothers), after being exposed to pups or to a non-social control stimulus (buttons). The results indicate that there are not significant differences between dams and godmothers in any of the observed variables. The only exception was a higher neural activity of the Pa nucleus in dams than in godmothers, irrespective of the stimuli they had been exposed to. Furthermore, the activity (density of c-FOS immunoreactive cells) in the analysed brain areas shows distinct patterns of correlation in the different experimental groups. This suggests that there are functional differences in the circuitry of maternal behaviour in female mice, which need to be studied in the future in order to understand how the maternal behaviour is regulated.