Abstract
Early separation of preterm infants from their mothers has adverse, long-term neurodevelopmental consequences. We investigated the effects of daily maternal separation (MS) of rat pups from postnatal days 2–10 (PND2–10) on neurobehavioural responses to brief isolation at PND12 compared with pups receiving controlled handling without MS. Ultrasonic vocalizations (USV) were measured at PND12 during two, 3-minute isolations occurring immediately before and after a 3-minute maternal reunion. There were no significant differences in acoustic characteristics between MS and control animals in the first isolation. However, in the second isolation, MS pups produced a greater proportion of high (~60 kHz) vs low (~40 kHz) frequency calls. During this isolation, control pups made longer and louder low frequency calls compared to the first isolation, whereas MS pups did the opposite. Maternal behaviour of control and MS mothers modulated pup acoustic characteristics in opposite directions; higher maternal care was associated with more low frequency calls in control pups but more high frequency calls in MS pups. We hypothesize that MS results in USV emission patterns reflective of a greater stress response to isolation. This translational model can be used to identify mechanisms and interventions that may be exploited to overcome the negative, long-term effects of MS.
Highlights
Due to medical necessity, preterm infants are cared for in neonatal intensive care units (NICU), where they are separated from their mothers for the majority of each day
We studied the effects of repeated maternal separation (MS), a model of low maternal care and early-life stress, on Ultrasonic vocalizations (USV) acoustic properties
We assessed whether natural variation in maternal care during early development shaped acoustic characteristics of USV production, with the hypothesis that more maternal care would mitigate changes in USV associated with MS
Summary
Preterm infants are cared for in neonatal intensive care units (NICU), where they are separated from their mothers for the majority of each day. At 18 months of age, FNI infants had improved cognitive and language scores on the Bayley, fewer attention problems on the Child Behavioural Check List, and decreased risk for socio-emotional problems as assessed by the Modified Checklist for Autism in Toddlers[7] These results have prompted increased interest in understanding the mechanistic underpinnings by which early maternal contact and emotional connection support infant development. Toward this end, here we have studied maternal separation and mother/pup interactions in rats as modulators of infant behavioural responses to the challenge of brief separation from their mothers. With the exception of studies using pups that were selectively bred for low and high call rates, it is unknown whether natural variation in maternal care during development shapes vocalization production[17]. We assessed whether natural variation in maternal care during early development shaped acoustic characteristics of USV production, with the hypothesis that more maternal care would mitigate changes in USV associated with MS
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