Effects of C2 hemisection on respiratory and cardiovascular functions in rats

High ce rvical spinal co rd injuries induce permanent neuromotor and autonomic deficits.These injuries impact both central respiratory and cardiovascular functions through modulation of the sympathetic nervous system.So far,cardiovascular studies have focused on models of complete contusion or transection at the lower cervical and thoracic levels and diaphragm activity evaluations using invasive methods.The present study aimed to evaluate the impact of C2 hemisection on different parameters representing vital functions(i.e.,respiratory function,cardiovascular,and renal filtration parameters) at the moment of injury and 7 days post-injury in rats.No ventilatory parameters evaluated by plethys mography were impacted during quiet breathing after 7 days post-injury,whereas permanent diaphragm hemiplegia was observed by ultrasound and confirmed by diaphragmatic electromyography in anesthetized rats.Interestingly,the mean arterial pressure was reduced immediately after C2 hemisection,with complete compensation at 7 days post-injury.Renal filtration was unaffected at 7 days post-injury;however,remnant systolic dysfunction chara cterized by a reduced left ventricular ejection fraction persisted at 7 days post-injury.Taken together,these results demonstrated that following C2 hemisection,diaphragm activity and systolic function are impa cted up to 7 days post-injury,whereas the respiratory and cardiovascular systems display vast ada ptation to maintain ventilatory parameters and blood pressure homeostasis,with the latter likely sustained by the remaining descending sympathetic inputs spared by the initial injury.A better broad characterization of the physiopathology of high cervical spinal cord injuries covering a longer time period post-injury could be beneficial for understanding evaluations of putative therapeutics to further increase cardiorespiratory recovery.