Developmental Window-Dependent Effects of Neonatal Tactile Stimulation on Sensorimotor Development in WAG/Rij Rat...

Background: Early-life sensory experiences play a crucial role in the maturation of neural circuits underlying sensorimotor development. The present study investigated whether the effects of neonatal tactile stimulation (NTS) on sensorimotor development depend on the developmental timing of the intervention in WAG/Rij rat pups, a well-established genetic model of absence epilepsy. Methods: Seventy rat pups were randomly assigned to five groups: Wistar control, WAG/Rij control, and WAG/Rij rats receiving NTS during the first (PN Week 1-NTS), second (PN Week 2-NTS), or third (PN Week 3-NTS) postnatal week. Tactile stimulation was administered three times daily. Sensorimotor development was assessed on postnatal day 22 using a modified rung-bridge task that evaluated orientation, flexor/extensor activity, distal control, gait development, postural control, sensorimotor responses, tail use, total sensorimotor performance, and crossing time. Results: WAG/Rij control pups exhibited impaired sensorimotor performance compared with Wistar controls, demonstrating lower distal control, gait development, sensorimotor response, and total sensorimotor scores, together with prolonged crossing times. The effects of the NTS protocol were dependent on the developmental window in which it was administered. The NTS protocol applied during the second postnatal week was associated with the most pronounced improvements, including significantly higher distal control, sensorimotor response, tail performance, and total sensorimotor scores, as well as significantly shorter crossing times compared with untreated WAG/Rij controls. In contrast, orientation, flexor/extensor activity, and postural control were not significantly affected. Discussion and Conclusions: These findings indicate that sensorimotor abnormalities are detectable in WAG/Rij rats during the early postnatal period, before the typical adult expression of absence seizures. The effects of the NTS protocol were strongly dependent on developmental timing, with the second postnatal week representing a particularly sensitive developmental window for sensorimotor maturation. Overall, the NTS protocol was associated with improved early sensorimotor performance in WAG/Rij rats, particularly when administered during the second postnatal week. Because a sham-handled control group was not included, these findings should be interpreted as reflecting the NTS protocol as a whole rather than tactile stimulation alone.