Effect Of Food Allergy Early In Life On Visceral Hyperalgesia In The Developing Rats And Role Of Substance P Abnormal Expression In Colon

Objective To establish food allergic (FA) models of ovalbumin (OVA) in developingSprague-Dawley (SD) rats. To explore the impact of food allergy on the visceral hyperalgesiaof developing rats and the role of SP abnormal expression in colon of FA rats with visceralhyperalgesia.Method20female SD rats about3-week old were randomly divided into two groups, the FAgroup and control group (NS)，10in each group. FA group was modeling through sensitizedintraperitoneally (i.p) with low-dose OVA and challenged by gavage with high-dose OVA.To evaluate the FA model, the change of serum OVA-IgE levels, morphological structureand the expression of eosinophils and the infiltrating situation of mast cells (MC) in jejunumwere observed. To evaluate the visceral pain sensitivity, the change of the amplitudes ofspike external oblique muscle of abdomen (EOMA) was measure at different colorectaldistension (CRD) pressures. Specimens of colons taken from intestine were used to analyzethe expression of SP through immunohisrochemical coloration and computer imageanalyzing system.SPSS13.0software for Windows was used in all statistical tests. The value of α=0.05wasconsidered significant.Result Most of SD rats in FA group showed bristling and lusterless, seldom moving,restlessness or diarrhea after challenges. The serum OVA-IgE concentration and theeosinophils, mast cell, the percentage of mast cells degranulation in jejunum in FA groupwere more than NS group. There was a significant difference between groups afterchallenged (P＜0.01). The amplitudes of spike EOMA(uV) of the FA group under the CRDpressures at0,15,30,45,60,75mmHg are17.74±0.72,18.63±1.72,22.55±1.70,28.63±7.00,33.97±7.34,37.26±8.4, and17.43±1.18,17.27±1.16,17.73±1.42,19.55±3.54,23.29±5.46,25.20±4.75in NS group.With the pressures of CRD added, the amplitudes of spike EOMAincreased significantly.There were significant differences between groups under the CRDpressures at30,45,60,75mmHg (F=47.470,13.367,13.317,15.390, all P＜0.01).Theexpressions of colons SP in FA group and NS group are247.12±90.83and103.90±58.94.There was a significant difference between groups(t=4.183, P＜0.01).Conclusion：Sensitized i.p with low-dose OVA and challenged by gavage with high-doseOVA, which can result in food allergy in developing SD rats, and build the OVA allergymodel. Food allergy early in life enabled the amplitudes of spike EOMA and the expression of colons SP increase significantly, which can lead to the development of visceralhyperalgesia.The occurrence mechanism of visceral pain hypersensitivity in this model maybe related to the increased number and degranulation of MS, and SP abnormal expression incolon.