Previous studies have shown that Roux-en-Y gastric bypass (RYGB), one of the most effective weight loss treatments for obesity, results in neurodegenerative responses in vagal afferent gut-brain connection reflected by microglia activation and reduced sensory input to the nucleus tractus solitarius (NTS). However, it is not known whether RYGB-induced microglia activation is the cause or an effect of the reported neuronal damage. Therefore, the aim of this study was to establish the order of neurodegenerative responses in vagal afferents after RYGB in the nodose ganglia (NG) and NTS in male and female rats. Sprague-Dawley rats were fed regular chow or an energy-dense diet for two weeks followed by RYGB or sham surgery. Twenty-four hours later, animals were sacrificed and NG and NTS were collected. Neuronal cell damage was determined by TUNEL assay. Microglia activation was determined by quantifying the fluorescent staining against the ionizing calcium adapter-binding molecule 1. Reorganization of vagal afferents was evaluated by fluorescent staining against isolectin 4. Results of the study revealed significantly increased DNA fragmentation in vagal neurons in the NG when observed at 24 h after RYGB. The surgery did not produce rapid changes in the density of vagal afferents and microglia activation in the NTS. These data indicate that decreased density of vagal afferents and increased microglia activation in the NTS likely ensue as a result of RYGB-induced neuronal damage.
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