Electrical stimulation of the vagus nerve improves intestinal blood flow after trauma and hemorrhagic shock

Background: Gut damage after trauma/hemorrhagic shock contributes to multiple organ dysfunction syndrome. Electrical vagal nerve stimulation is known to prevent gut damage in animal models of trauma/hemorrhagic shock by altering the gut inflammatory response; however, the effect of vagal nerve stimulation on intestinal blood flow, which is an essential function of the vagus nerve, is unknown. This study aimed to determine whether vagal nerve stimulation influences the abdominal vagus nerve activity, intestinal blood flow, gut injury, and the levels of autonomic neuropeptides. Methods: Male Sprague Dawley rats were anesthetized, and the cervical and abdominal vagus nerves were exposed. One pair of bipolar electrodes was attached to the cervical vagus nerve to stimulate it; another pair of bipolar electrodes were attached to the abdominal vagus nerve to measure action potentials. The rats underwent trauma/hemorrhagic shock (with maintenance of mean arterial pressure of 25 mmHg for 30 min) without fluid resuscitation and received cervical vagal nerve stimulation post-injury. A separate cohort of animals were subjected to transection of the abdominal vagus nerve (vagotomy) just before the start of cervical vagal nerve stimulation. Intestinal blood flow was measured by laser Doppler flowmetry. Gut injury and noradrenaline level in the portal venous plasma were also assessed. Results: Vagal nerve stimulation evoked action potentials in the abdominal vagus nerve and caused a 2-fold increase in intestinal blood flow compared to the shock phase (P < .05). Abdominal vagotomy eliminated the effect of vagal nerve stimulation on intestinal blood flow (P < .05). Vagal nerve stimulation protected against trauma/hemorrhagic shock -induced gut injury (P < .05), and circulating noradrenaline levels were decreased after vagal nerve stimulation (P < .05). Conclusion: Cervical vagal nerve stimulation evoked abdominal vagal nerve activity and relieved the trauma/hemorrhagic shock–induced impairment in intestinal blood flow by modulating the vasoconstriction effect of noradrenaline, which provides new insight into the protective effect of vagal nerve stimulation.