Functional neuroanatomy of maternal motivation : role of oxytocinergic circuits in the social brain of mice

Abstract

During pregnancy, the future mothers’ brain is exposed to a wide variety of hormones that increase her sensitivity to offspring and facilitate maternal behaviour. Literature describes oxytocin has a key role in the neural circuits responsible for these responses. For this reason, our hypothesis is that the expression of oxytocin is modified in the socio-sexual brain during motherhood. To do this, a motivated maternal behaviour test (collecting pups in a paradigm of physical exertion) has been performed on lactating dams, virgins exposed to pups and virgins without sensitization; and we counted the number of neurons that expressed oxytocin in the hypothalamic paraventricular nucleus, preoptic area and nucleus of the stria terminalis; and calculated the density of oxytocinergic (OTergic) fibres in key centres of the socio-sexual brain (nucleus accumbens and central amygdala). In this study we have used data from the latest studies by Salais-López, (2017) and Lacomba (2020). Our results indicate that motherhood induces a high motivation in dams to retrieve the pups. We only found significant differences in the length of oxytocin fibres in the central amygdala between mothers and virgins (higher in mothers), with no differences between the rest of the nuclei studied, so we excluded the hypothesis formulated. On the other hand, motivated maternal behaviour (summation of the inverse latency to the collection of all the offspring collected) is significantly and positively correlated with the density of OTergic fibres to the nucleus accumbens, but only in dams. This suggests that motherhood promotes OTergic neuroplasticity in specific areas.