Abstract
Nesfatin-1, a satiety molecule processed from nucleobindin2 (NUCB2), is implicated in visceral hypersensitivity in rats and colocalized with 5-hydroxytryptamine (5-HT) in the dorsal raphe nucleus (DRN). Maternal separation (MS) in rats contributes to visceral hypersensitivity via elevated expression of 5-HT in the DRN. Intracerebroventricular injection of nesfatin-1 activates DRN 5-HT neurons. In this study, A model of visceral hypersensitivity was developed by subjecting rats to MS. Colorectal distension was used to detect visceral sensitivity, which was evaluated by abdominal withdrawal reflex (AWR) scores and electromyogram (EMG) magnitude. MS rats exhibited higher AWR scores and EMG magnitude compared with controls. The numbers of nesfatin-1- and tryptophan hydroxylase (TPH, the rate-limiting enzyme for 5-HT synthesis)-positive cells in the DRN were significantly elevated accordingly. Visceral hypersensitivity was significantly alleviated in MS rats treated with intra-DRN administration of anti-nesfatin-1/NUCB2, accompanied by decreased expression of 5-HT and TPH in the DRN, compared with the vehicle-treated group. In contrast, intra-DRN administration of nesfatin-1 into normal adult rats induced visceral hypersensitivity, which correlated with elevated expression of 5-HT and TPH in the DRN. In conclusion, Nesfatin-1 has critical effects on visceral hypersensitivity; the underlying mechanisms might be related to the activation of DRN 5-HT neurons.
Highlights
Irritable bowel syndrome (IBS) is a chronic gastroenterological disease of uncertain etiology marked by abdominal pain or discomfort and disorder of bowel movements
maternal separation (MS) rats exhibited higher abdominal withdrawal reflex (AWR) score [p = 0.01; p = 0.01; p = 0.009; n = 6 for each group] (Fig. 2A) and more intensive EMG magnitude [p = 0.035; p = 0.015; p = 0.009; n = 6 for each group] (Fig. 2B) at strengths of 40, 60, and 80 mmHg colorectal distension (CRD) pressure when compared to normally handled (NH) rats
We found that intra-dorsal raphe nucleus (DRN) injection of anti-nesfatin-1/NUCB2 in MS rats resulted in a significant decline in the AWR scores at 40, 60, and 80 mmHg distension pressures [p = 0.015; p = 0.005; p < 0.001; n = 6 for each group] (Fig. 4A) and EMG magnitude at all distension pressures [p = 0.044; p = 0.024; p = 0.002; p < 0.001; n = 6 for each group] (Fig. 4B), as compared with vehicle-treated rats
Summary
Irritable bowel syndrome (IBS) is a chronic gastroenterological disease of uncertain etiology marked by abdominal pain or discomfort and disorder of bowel movements. Enteric 5-HT interacts with 5-HT3 receptors via afferent fibers that connect the gut with the central stress circuit (paraventricular nucleus, hippocampus, amygdala, locus coeruleus, and the raphe nucleus)[4] These cerebral areas are abnormally activated due to chronic exteroceptive stress, leading to a local release of 5-HT, which may facilitate visceral pain processing via efferent fibers, and further result in visceral hypersensitivity[7]. Intracerebroventricular administration of nesfatin-1 activates corticotropin-releasing hormone (CRH), noradrenaline and 5-HT neurons, and induces the HPA axis[13] Previous studies by these authors demonstrated that nesfatin-1 is implicated in visceral hypersensitivity[14]. We sought to determine the effect of nesfatin-1 in the DRN on visceral sensitivity using a maternally separated rat model of IBS. Effects of nesfatin-1 on visceral hypersensitivity and DRN 5-HT neurons were studied
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