| 研究実績の概要 |
Irritable bowel syndrome (IBS) is a chronic functional gastrointestinal disorder characterized by recurrent abdominal pain and abnormal bowel patterns. Little is known about neurotransmitters and neuromodulators which crucially regulate the pathophysiology of IBS. The aim of this study was to determine the neurotransmitter and neuromodulator including corticotropin-releasing hormone (CRH) in IBS.
We made rat model of IBS with colorectal distention (CRD). CRD was performed with computerized barostat system and visceral sensitivity was evaluated with visceromotor response (VMR) by electromyogram. We made the experimental system for testing neurotransmission modulated by administration of vehicle, CRH agonist and CRH antagonist. Counting the number of fecal pellets for 60 min after the drug/vehicle injection evaluated colonic motor function. Anxiety-related behavior was measured for 5 minutes during exposure to an elevated-plus maze (EPM).
We made the experimental system to extend the experiment to the other neurotransmitters and neuromodulators and their receptors. It included morphological changes of the neurons and the glia cells in rats of IBS model. Quantification of the data, statistical analyses, and writing manuscripts were prepared.
We required the maximum amount of the grant by the following reasons; 1) We needed new experimental kits for the assay, 2) We needed multiple experiments to determine statistically optimal doses of CRH agonist and CRH antagonist, 3) CRH receptors are highly possible to play crucial roles in the pathogenesis of IBS.
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| 現在までの達成度 (区分) |
現在までの達成度 (区分)
2: おおむね順調に進展している
理由
Male Wistar rats (age 6 weeks, weighing 160-211; 200 g) were divided into four groups. Either vehicle or CRH-R1 antagonist (CP-154,526, 20mg kg-1, sc) was injected subcutaneously 30 min before intraperitoneal injection of cortagine (10ug kg-1, ip) or vehicle. Then CRD was performed two times over 20 minutes (20, 40, 60, or 80 mmHg for 20 seconds at 2 minutes intervals). The electromyography (EMG) recordings were collected which is to measure the visceromotor responses (VMR) that accompanied the CRD. The rats were allowed to recover for 20minutes. Anxiety-related behavior was measured for 5 minutes during exposure to an elevated-plus maze (EPM).
Compared with vehicle, cortagine significantly induced increase in fecal pellets number (2.43 ± 0.48 vs. 0.17 ± 0.17 pellets/h, P < 0.05). CP-154,526 abolished the cortagine-induced fecal pellets output (0.43 ± 0.30 vs. 2.43 ± 0.48 pellets/h, P < 0.05). The amplitude of EMG has significant difference among four groups (F = 5.94, P < 0.01). EMG amplitude in cortagine group was significantly higher than that of control and CP group (P < 0.05). CP-154,526 has significantly decreased EMG amplitude, compared with cortagine group (P < 0.05). The total travel distance in the EPM has significantly differences among four groups (F = 4.68, P = 0.01). Compared with vehicle, cortagine significantly decreased total travel distance (878.5 ± 76.5 vs. 1312.9 ± 49.9cm, P < 0.05). However CP-154,526 significantly increased the total travel distance compared with cortagine (1255.3±115.0 vs. 878.5 ± 76.5cm, P < 0.05).
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| 今後の研究の推進方策 |
Corticotropin-releasing hormone (CRH) and its receptors play important roles on colonic response to stress. Activation of CRH receptor 1 in the brain is a key to stress induced changes in gastrointestinal function and emotion. Cortagine, a selective CRH-R1 agonist, has been demonstrated to induce stress-like colonic alterations in rats by intraperitoneal injection. We tested the hypothesis that peripheral cortagine injection induces colonic visceromotor dysfunction as well as anxiety behavior, which are blocked by selective CRH-R1 antagonist. Peripheral cortagine injection can stimulate defecation, induce visceral hypersensitivity and anxiety-related behaviour as well, which were all abolished by CRH-R1 antagonist. The results will be presented at the American Gastroenterological Association in the Digestive Disease Week 2018. Progression of this study is just as scheduled. The great impact of this study on the progression of science and medicine was warranted.
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