Dr. Yoichiro Sugiyama

Abstract:

Dysphagia has become a significant and increasingly widespread issue, especially given the rapidly aging global population. Various factors, such as cerebrovascular lesions and neurodegenerative diseases, can lead to swallowing impairments. Specifically, brainstem ischemia in the dorsolateral medulla and other brainstem regions, such as the dorsolateral pons, can result in severe swallowing disorders, ultimately leading to aspiration pneumonia. Moreover, reoxygenation during reperfusion after ischemic brain damage triggers oxidative reactions of reactive oxygen species (ROS) in the ischemic and surrounding areas, which can exacerbate neuronal damage in and around the ischemic lesion. However, our understanding of how ischemia and reperfusion in the brainstem affect swallowing function and oxidative stress is limited.

To clarify the impact of brainstem ischemia and subsequent reperfusion on swallowing function and oxidative stress, we studied changes in motor activities of respiration and swallowing, as well as oxidative stress, before, during, and after brainstem ischemia induced by transient clamping of the carotid or vertebral arteries. 

We monitored respiration and swallowing by recording the activity of the vagus, hypoglossal, phrenic, and abdominal nerves in a perfused brainstem preparation of rats. Swallowing was induced through electrical stimulation of the superior laryngeal nerve and by administering water orally. We analyzed changes in respiratory rhythm and motor activities and measured derivatives of reactive oxygen metabolites (d-ROMs) and biological antioxidant potential (BAP) to evaluate the levels of oxidative and antioxidative stress before, during, and after the clamping of the bilateral carotid artery (group 1) and the ipsilateral vertebral artery (group 2).

The respiratory-related and swallowing-related activities of the vagus and hypoglossal nerves were modestly altered following the clamping of the arteries. The BAP levels tended to be increased after reperfusion.

Our findings suggest that brainstem ischemia and subsequent reperfusion mediate changes in respiratory and swallowing function concurrent with alterations in the oxidative and antioxidative balance.