Resumen de The medial amygdala as a key neural centre in maternal aggression: genetic, neural and behavioural analysis
In rodents, as macrosmatic animals, chemosensory processing plays an instrumental role in guiding the expression of social, sexual and maternal behaviours. Social odours and pheromones are processed by the main and the accessory olfactory systems, which information converge mainly in the medial amygdala (Me). The Me, in turn, plays a central role in the vomeronasal–sensorimotor integration that leads to specific behavioural responses such as the above-mentioned social and maternal behaviours.
Maternal behaviour comprises physiological and behavioural adaptations that help the dams to successfully raise their offspring. This behaviour is expressed in a wide range of vertebrate species and can be parsed in two main components, namely pup-directed (i.e. maternal care), and non-pup-directed behaviour as maternal aggression. Previous studies have shown that pup-sensitized virgin females, which display all pup-directed behaviours towards pups, do not show maternal aggression towards male intruders.
The main goal of this thesis is to investigate the role of Me in the control of maternal aggression and the possible adaptations that this nucleus suffers during lactation, such as changes in gene and protein expression.
The results of the experiments inducing a chemogenetic inhibition of Me showed that this nucleus is a key centre in the neural control of maternal aggression. One of the main changes in the Me of dams revealed by our RNA-seq study was an increased PRL expression. Thus, we characterized the prolactinergic (PRLergic) circuits in female brain in different physiological states. The same pattern of PRLergic immunoreactivity was present in pup-sensitized, pup-naïve virgins and lactating female mice. However, we found quantitative differences between dams and the other two groups in the supraoptic nucleus and between dams and virgin naïve females in the suprachiasmatic and the medial preoptic nucleus.
Our findings shown a widespread PRL innervation in the female mouse brain, suggesting the existence of important PRLergic pathways. In addition, these pathways suffer some adaptations during lactation. This supports a role for PRL as a neuroactive peptide, in addition to its well-documented endocrine role.
In conclusion, hormonal changes linked to pregnancy, parturition and lactation induce modifications of the socio-sexual brain network, including effects on the transcriptomic profile of the Me and the central PRLergic systems. These modifications might contribute to the expression of behaviours specifically linked to motherhood, such as maternal aggression.
