Neural mechanism of acupuncture-modulated gastric motility

AIM: To investigate the acupuncture-modulated gastric motility and its underlying neural mechanism.METHODS: Intragastric pressure and/or waves of gastric contraction in rats were recorded by intrapyloric balloon and changes of gastric motility induced by acupuncture stimulation were compared with the background activity before any stimulation. Gastro-vagal or splanchnic-sympathetic nerves were recorded or cut respectively for investigating the involvement of autonomic nerve pathways. Spinalization experiment was also performed.RESULTS: Acupuncture-stimulation by exciting Aδ and/or C afferent fibers, could only modulate gastric motility. Acupuncture-stimulation on fore- and hind-limbs evoked a moderate gastric motility followed by increased vagus discharges with unchanged sympathetic activity, while the same stimulus to the acupoints in abdomen resulted in reversed effects on gastric motility and autonomic nervous activities. The inhibitory gastric response was completely abolished by splanchnic denervation, but the facilitative gastric response to stimulation of acupoints in limbs was not influenced, which was opposite to the effect when vagotomy was performed. The similar depressive effects were produced by the stimulation at the acupoints homo-segmental to the gastric innervation in the animals with or without spinalization. However, the facilitation induced by the stimulation at the acupoints hetero-segmental to the gastric innervation was not observed in the spinalized animals.CONCLUSION: Facilitative effects of stimulating hetero-segmental acupoints are involved in the intact preparation of vagal nerves and spinal cord, while the inhibitory response induced by stimulating homo-segmental acupoints is involved in the intact preparation of sympathetic nerves. Only the acupuncture-stimulation with intensity over the threshold of Aδ and/or C afferent fibers can markedly modulate gastrointestinal motility.

Identifying a Safe Range of Stimulation Current for Intraoperative Neuromonitoring of the Recurrent Laryngeal Nerve： Results from a Canine Model

Background： lntraoperative neuromonitoring （IONM） of the recunent laryngeal nerve （RLN） has been widely applied during thyroid surgery. However, the sale range of stimulation intensity for IONM remains undetermined, Methods： Total thyroidectomies were performed on twenty dogs, and their RLNs were stimulated with a current of 5 20 mA （step-wise in 5 mA increments） for 1 min. The evoked electromyography （EMG） of vocal muscles before and after supramaximal stimulation were recorded and compared. Acute microstructural morphological changes in the RLNs were observed immediately postoperatively under an electron microscope. Results： The average stimulating threshold for RLNs stimulated with 15 mA and 20 mA showed no significant changes compared to the unstimulated RLNs （15 mA group： 0.320 ± 0.123 mA vs. 0.315 ±0.097 mA, P =0.847; 20 mA group： 0.305 ± 0.101 mA vs. 0.300 ＋ 0.103 mA, P = 0.758）. Similar outcomes were shown in average evoked EMG amplitude （15 mA group： 1,026 ± 268 p.V xs. 1,021 ± 273 p.V, P = 0.834; 20 mA group： 1,162 ± 275 μV vs. 1,200 ± 258μV, P = 0.148）. However, obvious acute microstructural morphological changes were observed in the nerves that were stimulated with 20 mA. Conclusions： A stimulation intensity less than 15 mA might be safe for IONM of the RLN.