Neuroendocrine control of maternal behaviour
Caughey, Sarah Dawn
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Maternal behaviour during the peri-partum period, albeit in differing forms, can be observed in all mammals, thus it must serve an important evolutionary purpose in enabling the successful raising of offspring. Maternal behaviour is comprised of a large suite of behaviours; in rodents these are generally defined as lactation, pup retrieval, maternal aggression and pup grooming. The maternal behaviour circuitry involves many brain regions including the hypothalamus and the limbic system which work together to regulate the motor, motivational and emotional demands of the lactation period. The main aim of this thesis is to understand how different neuromodulators, specifically oxytocin (OXT), vasopressin (AVP), allopregnanolone (AP) and GABA, influence the expression of maternal behaviour, especially maternal aggression, and where in the brain they act to control this. Maternal aggression in rats changes dramatically throughout pregnancy, parturition and lactation. This expression is highly influenced by pups and during early lactation, pup cues are essential in maintaining it. Towards the end of lactation pup cues appear to result in the down regulation of maternal aggression. The maternal aggression circuitry is highly complex and involves many of the brain regions highlighted to be involved in maternal behaviour. The neuropeptides, OXT and AVP, are observed to have significant changes in their systems that correlate with maternal aggression, specifically within the BnST and PVN. This leads to the proposal they work oppositely to control maternal aggression by regulating fear and anxiety in the lactating rat. There is also evidence the OXT system mediates the motor output of maternal aggression. AP and GABA are also important in maternal behaviour, especially in relation to fear; whether this in context with OXT to enable maternal aggression or if they are a back up mechanism for OXT secretion malfunctioning remains to be determined. By understanding the complex maternal behaviour neural circuitry and how neuromodulators work to control it, enables the development of potential therapies for disorders a woman may experience during the peri-partum period. Prevention of these disorders is not only beneficial to the mother and her immediate family but is also crucial for her offspring’s development in prevention of adulthood disorders stemming from their childhood experience which can impact their own paternal or maternal care ability.