Moderate 3D orbital shaking mitigates maternal separation-induced neurodevelopmental impairments in rats

Maternal separation during early life is a well-established model for inducing neurodevelopmental impairments and increasing hippocampal vulnerability. Externally generated mechanosensory stimulation, such as three-dimensional orbital shaking (3D-OS), has been proposed as a candidate modulatory stimulus in cellular and organoid models, but its impact on neonatal brain development under early-life stress conditions remains unknown. We investigated whether 3D-OS, applied as a controlled postnatal mechanosensory stimulation, could partially attenuate behavioural, histological, and molecular alterations induced by maternal separation in rats. Eighteen newborn Sprague Dawley rats were assigned to control (C), maternal separation (MS), or maternal separation plus orbital shaking (MSOS) groups. Maternal separation was performed 3 h/day between postnatal days 2-21; MSOS additionally received 3D-OS (25 rpm, 3 h/day) as a rocking cradle-like mechanosensory stimulation. Behavioural tests (Open Field, Novel Object Recognition, Morris Water Maze, Passive Avoidance), combined with RT-qPCR, Western blot, histology, and immunohistochemistry were conducted. Compared with MS, MSOS rats showed partial improvement in early Morris Water Maze performance and longer step-through latency in the retention phase of Passive Avoidance, whereas Open Field, Novel Object Recognition, and Western blot analyses did not reveal significant inter-group differences. Histological analysis showed reduced neuronal loss and vacuolisation in hippocampal and cortical regions of MSOS rats. RT-qPCR demonstrated reduced hippocampal FGF2 and FGFR1 expression in MS, with values in MSOS shifting toward control levels, whereas immunohistochemistry showed a receptor-specific pattern that was not fully concordant with the transcript data. Early-life 3D-OS administration alleviated maternal separation-induced cognitive decline and structural impairments and modulated hippocampal FGF2-FGFR signalling markers, proposing a neuroprotective effect of externally generated mechanosensory stimulation under early-life stress. These findings provide preclinical evidence that gentle mechanosensory stimulation may support early brain development and mitigate stress-related neurodevelopmental vulnerability.