Intestinal electric stimulation modulates neuronal activity in the nucleus of the solitary tract in rats

Intestinal electric stimulation (IES) has been shown to produce an inhibitory effect on gastric motility and secretion. The possible central mechanism of this entero-gastric inhibitory effect induced by IES is unknown. The objective of this study was to evaluate the effects of various IES on the activity of neurons in nucleus tractus solitarii (NTS). We examined the extracellular neuronal activity in NTS of the medulla in pentobarbital anesthetized, paralyzed, ventilated male adult rats. The aortic depressor, superior laryngeal, and carotid sinus nerves were crushed or sectioned bilaterally to avoid neuronal responses in NTS to cardiovascular baroreceptors. After NTS neurons with gastric input were identified, responses of single neurons in NTS to IES were determined. IES with different parameters was performed via a pair of platinum electrodes sutured onto the serosal surface of the duodenum 2 cm below the pylorus. IES with different parameters activated 39-72% of the solitary tract nucleus neurons responsive to gastric distension. Moreover, we demonstrated that IES activated the neuronal activity in NTS, which was stimulation energy dependent. The modulatory effect of IES on the central neurons receiving vagal inputs may contribute to the neural mechanisms of IES therapy for the treatment of patients with obesity and gastrointestinal motility disorders.