INVESTIGATING THE BRAIN CRF AND OXT SYSTEMS IN THE NUCLEUS ACCUMBENS: IMPLICATIONS FOR POOR MOTHERING IN LACTATING RATS

Females undergo various adaptations to prepare for motherhood, resulting in a balanced interplay of various neurotransmitter systems, like corticotropin-releasing factor (CRF) and oxytocin (OXT). Their dysregulation can potentially lead to maternal neglect. The nucleus accumbens (NAc), a heterogenous brain region at the interface of the reward and maternal circuits, plays a key role in these processes. Here, we investigated the NAc CRF and OXT systems’ involvement in maternal behaviour in early lactating rats. First, maternal aggression was monitored during the maternal defence test (MDT) against a virgin female intruder after bilateral, local injections of vehicle or CRF (1µg/0.5µL/side) in the NAc shell. In addition, maternal care was monitored before and after the MDT. Acute CRF infusion reduced the number of attacks and total nursing. In those brains, whole-brain c-Fos mapping revealed differential activation of various brain regions due to exposure to MDT/CRF. Microdialysis during the MDT revealed increased intra-NAc OXT release during maternal defence. Interestingly, retrodialysis of CRF, but not of UCN3, also resulted in OXT release within the NAc. Unilateral microinfusion of a retrograde transported virus in the NAc shell of virgin female rats revealed CRF+ projections descending from the basolateral amygdala, medial prefrontal cortex, and paraventricular thalamus. Using in-situ hybridisation, we further characterised the nature of CRF receptor-expressing neurons in the NAc, indicating differential expression of Crhr1 and Crhr2 throughout the NAc. This research highlights the critical role of NAc CRF and OXT in regulating maternal behaviour and provides novel insights into the NAc’s neuronal underpinnings.