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The experiments reported in this thesis examined the long-term effects of chronic maternal-separation on the mother and her future offspring. Adult female rats were bred and were then repeatedly separated from their pups (maternal separation; MS) or remained with their pups (standard rearing; SR). After those pups were weaned, females were bred again with all pups from the subsequent litters being standard reared. Hence, these subsequent litter pups had mothers that were either previously separated (MSSUB) or not (SRSUB) from their prior litter. Infant offspring of the subsequent litter and their mothers were the focus of the research reported in this thesis. In the first series of experiments (Chapter 2), those infants were examined for anxiety-like behaviour, as well as whether they use maternal cues to regulate their responses to aversive situations, a process referred to as maternal buffering. It was found that MSSUB infants did not exhibit more anxiety-like behaviour compared to standard-reared controls. However, these infants exhibited impaired maternal buffering in response to aversive stimulation. The second series of experiments (Chapter 3) examined whether alterations in mother-infant attachment might underlie the atypical learned fear behaviour that has been previously demonstrated in MSSUB infants (Kan et al., 2016) and the impaired maternal buffering observed in Chapter 2. It was found that mothers with a stress history do not behave differently towards their future offspring when they are undisturbed in the nest. However, under more challenging situations (i.e., when briefly separated from her offspring), mothers that were previously-stressed retrieve their offspring significantly faster, compared to non-stressed mothers. The third and final series of experiment (Chapter 4) examined behavioural and biological factors in the mother following previous exposure to stress. While previously-stressed mothers did not differ from controls on biological measures, such as serum levels of corticosterone, these mothers exhibited behavioural differences on measures of cognition. Specifically, previously-stressed mothers showed poorer spatial learning, compared to non-stressed mothers. These findings are discussed in terms of broader clinical implications for targeting the mother to prevent the intergenerational transmission of stress effects.

Abstract Purpose: To investigate the efficacy of xylitol-containing wipes on reducing maternal and non-maternal transmission of mutans streptococci (MS) in infants aged 6-35 months. Methods: Forty-four mother-infant pairs participated in a double-blinded randomized controlled clinical trial, and were assigned to xylitol-wipe or placebo-wipe groups. Mothers were instructed to use 2 wipes 3 times daily for their infants. Saliva samples were collected from mothers and infants at baseline, 3 months, 6 months, and 1 year for MS enumeration and colonies of 21 mother-infant pairs were genotyped by arbitrarily primed polymerase chain reaction. Results: All mothers assessed had MS infection. MS colonization was found in 12 infants, with maternal transmission only in 4 infants. There was no significant difference in MS colonization rates of infants in the xylitol (56%) and placebo wipe groups (76%) at 1 year, but more diverse and less retained MS genotypes were noted in xylitol wipe group. Maternal MS strains only accounted for 9% of total genotypes in these infants. Most non-maternal MS genotypes were transient (92%), whereas most maternal transmitted MS genotypes were retained (80%). Conclusions: Non-maternal MS transmission is an important source for MS colonization in infants. Daily xylitol wipe use may affect the sustainability of MS in infant.