Acute perinatal asphyxia at birth has long-term effects on behavioural arousal and maternal behaviour in lactating rats

Abstract

This study analysed the long-term consequences of an asphyctic event at birth on maternal behaviour and emotionality in rats. Pregnant Wistar rats were delivered by Caesarean section and the pups, still in the uterus horns, were placed into a water bath at 37 °C for periods of 0 (Caesarean delivery, CD) or 20 min (asphyxia, CD + 20). Control subjects were born by vaginal delivery (VD). Subsequently, pups were given to surrogate mothers, weaned at 21 days, and mated at adulthood. After giving birth, differences in maternal competence and behavioural arousal were assessed observing: (i) maternal behaviour after reunion with the pups following a 3 h separation, on postpartum day (PPD) 4; (ii) behaviour in an elevated plus-maze test, on postpartum day 7; and (iii) performance in a fear conditioning test, in which subjects learned to associate a conditional stimulus with an aversive unconditioned stimulus (postpartum days 7–8). Results indicate that subjects in the CD + 20 group showed a deficit in maternal care, taking a longer time to retrieve the whole litter and often failing to retrieve all pups. Both CD and CD + 20 groups showed higher behavioural activity in the plus-maze. In addition, when tested in the fear conditioning paradigm, the CD + 20 group showed a lower latency to perform freezing behaviour in the auditory cue trial. The changes in behavioural arousal described suggest that the dopaminergic system may be a potential neurochemical target for an early hypoxic insult and indicate maternal behaviour as a useful endpoint to study the effects of early birth insult on brain function.