Novel Non-Invasive Method To Assess Colonic Motility In Conscious Mice: Influence Of Various Stressors

are attenuated by pretreatment with 5-HT 2A/2C stimulation.Methods: The neonatal Wistar rat pups received a subcutaneous injection of either saline or 5-HT 2A/2C agonist (±)-1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane HCl (DOI)(0.5mg/kg)every day, and the injection was given 15 min before the maternal separation (MS) manipulation for 180 min daily during 2-14 postnatal days.After growing, rats were exposed to the elevated plus maze (EPM) to measure anxiety-like behavior and colonic motor function.The visceromotor response was evaluated by electromyogram of the abdominal muscle in response to phasic colorectal distention (CRD) (20, 40, 60, and 80 mmHg) for three times.On the next day, tonic CRD (60 mmHg; 15min duration) was loaded to measure plasma adrenocorticoticotropic hormone and serum corticosterone.Results: MS rats spent significantly more time (60.6±6.1%) in the closed arms than controls (43.4±5.3%, p<0.05).MS rats showed significantly more fecal pellet output (3.3±0.8)during the EPM than controls (1.0±0.6,p<0.05).MS rats expressed significantly more visceromotor response to phasic CRD than controls (p=0.001).Administration of DOI significantly reduced anxiety (40.9±2.7%,p<0.05) and fecal pellet output (1.2±0.5, p<0.05) in DOI+MS rats compared with MS rats.The significant difference in visceromotor response between controls and MS rats was also abolished by DOI.Conclusions: Our results support the hypotheses that rats after the maternal separation show anxiety, colonic hypermotility and visceral hypersensitivity, and that administration 5-HT 2A/2C receptor agonist reverses these changes.The results suggest a salient role of 5-HT 2A/2C pathway in the development of pathophysiology mimicking IBS.