The effects of low-and high-frequency non-invasive transcutaneous auricular vagal nerve stimulation (taVNS) on gastric slow waves evaluated using in vivo high-resolution mapping in porcine.

BACKGROUNDS: Gastric motility is regulated by an electrophysiological activity called slow-wave and neuronal innervations by the vagus nerve. Transcutaneous auricular vagal nerve stimulation (taVNS) has been demonstrated to have therapeutic potential for a wide range of medical conditions, including the management of gastric dysfunctions. The main objective of this study was to gain a better understanding of how non-invasive neuromodulation influences gastric slow wave under in vivo conditions. METHODS: TaVNS protocols were applied in conjunction with 192-channel gastric bioelectrical mapping in porcine subjects under general anesthesia. The spatiotemporal profiles of gastric slow wave were assessed under two different taVNS protocols at 10 and 80 Hz. KEY RESULTS: The taVNS protocols effectively altered the interval and amplitude of gastric slow waves, but not the velocity or the percentage of spatial dysrhythmias. In the subjects that responded to the protocols, the 10 Hz protocol was shown to normalize slow-wave propagation pattern in 90% of the subjects, whereas the 80 Hz protocol was shown to inhibit slow waves in 60% of the subjects. CONCLUSIONS AND INFERENCES: Chronic responses of gastric motility and slow waves in response to taVNS should be investigated using non-invasive means in conscious subjects in future.

Endomicroscopic optical coherence tomography for cellular resolution imaging of gastrointestinal tracts.

Our ability to detect neoplastic changes in gastrointestinal (GI) tracts is limited by the lack of an endomicroscopic imaging tool that provides cellular-level structural details of GI mucosa over a large tissue area. In this article, we report a fiber-optic-based micro-optical coherence tomography (µOCT) system and demonstrate its capability to acquire cellular-level details of GI tissue through circumferential scanning. The system achieves an axial resolution of 2.48 µm in air and a transverse resolution of 4.8 µm with a depth-of-focus (DOF) of ~150 µm. To mitigate the issue of limited DOF, we used a rigid sheath to maintain a circular lumen and center the distal-end optics. The sensitivity is tested to be 98.8 dB with an illumination power of 15.6 mW on the sample. With fresh swine colon tissues imaged ex vivo, detailed structures such as crypt lumens and goblet cells can be clearly resolved, demonstrating that this fiber-optic µOCT system is capable of visualizing cellular-level morphological features. We also demonstrate that time-lapsed frame averaging and imaging speckle reduction are essential for clearly visualizing cellular-level details. Further development of a clinically viable µOCT endomicroscope is likely to improve the diagnostic outcome of GI cancers.