Maternal care and pup ultrasonic vocalizations (USVs) as early markers of PTSD susceptibility in rats

Background: PTSD is a chronic psychiatric disease that may develop following trauma [1,2]. While only a subset of individuals becomes susceptible to PTSD, most fully recover after the initial acute physiological response [3].Early-life trauma and the quality of maternal caregiving may contribute to intergenerational transmission of stress vulnerability [4]. We examined early maternal care, and early-life offspring behaviors and ultrasonic vocalizations (USVs) in PTSD susceptible (SUS) rats [5,6]. Methods: PTSD-like SUS [5,6] and control (CTRL) Sprague–Dawley female rats and their offspring were used. On postnatal day (PND) 1, litters were culled to a standardized size (4 females and 4 males). Maternal behavior was evaluated across PND 2-13 [7]. In offspring, USVs (30-70 kHz range) and behavior [8] were assessed on PND 5, 7, 9, 11, 13; a separate cohort underwent the homing test (PND 13), during which both USVs and behavior were analyzed. Results: Compared with CTRL, SUS dams showed an overall increase in maternal care and reduced non-maternal behaviors across PND 2–13. Moreover, SUS pups emitted more USVs at PND 5 and 7 and displayed different behavioral repertoire, consistent with heightened arousal and altered self-directed and motor patterns. In the homing test, SUS pups produced more and longer USVs, while nest-reaching latency and time spent in the nest were comparable between groups. Conclusions: PTSD susceptibility is accompanied by early changes in maternal care and offspring emotional reactivity. SUS dams provide more caregiving, yet SUS pups display altered distress-related USVs and behavioral responses. References: [1] American Psychiatric Association, 2013. Diagnostic and Statistical Manual of Mental Disorders (DSM-5), 5th ed. American Psychiatric Publishing. [2] Yehuda et al., 2015. Nat Rev Dis Primers, 1:15057. [3] Lewis et al., 2019. Lancet Psychiatry, 6(3):247–256. [4] Klengel et al., 2016. Neuropsychopharmacology, 41(1):219–231. [5] Berardi et al., 2014. Front Behav Neurosci, 8:142. [6] Colucci et al., 2020. Transl Psychiatry, 10(1):243. [7] Colucci et al., 2020. Behav Brain Res, 392:112723. [8] Branchi et al., 2004. Behav Brain Res, 151(1–2):9–16.