Numerous preclinical studies demonstrate that vagus nerve stimulation (VNS) paired with motor rehabilitation improves functional recovery after neural injuries such as stroke, traumatic brain injury, and spinal cord injury, in part by driving neural plasticity within the motor cortex. To date, these studies have been performed almost exclusively in female rats, however, the risk for neural injuries of all types is significantly higher among males than females. We therefore sought to determine whether VNS was equally effective at driving motor cortical plasticity in both sexes. Male and female rats were trained on a skilled lever press task prior to VNS electrode implantation. After recovery, rats received ten training sessions in which VNS, or sham stimulation, was paired with correct motor performance. At the completion of these treatment sessions, somatotopic mapping of motor cortex was performed. We found that performance on the lever task was similar between male and female rats, though on average, males performed more trials per training session, consistent with their larger size and higher caloric need. Training-paired VNS effectively induced cortical motor map reorganization in both male and female rats. Notably, we also found that VNS reduced lever-press associated caloric intake during treatment in both sexes. These VNS-driven effects were robust to behavioral and biological differences between male and female subjects. Taken together, our results suggest that, in both male and female rats, VNS simultaneously engages both pro-plasticity neuromodulation within the neocortex and satiety or reward-related networks that reduce task-associated caloric intake.
Keywords: Cortical plasticity; Motor cortex; Motor learning; Sex differences; Vagus nerve stimulation.
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