The Influence And Mechanism Of Small Does Of Capsaicin On Sensibility Of Visceral Mechanical And Chemical Stimulation In Rats

bjective: To investigate the effects and mechanism of capsaicin(CAP)on sensibility of visceral mechanical and chemical stimulation in rats in different period,through testing the sensitivity of visceral mechanical and chemical stimulation in rats after ingesting small dose of CAP, detecting the expression of transient receptor potential type 1 in gastric and duodenal mucosal and the barrier of gastric and duodenal mucosal。Methods :(1)The preparation of CAP feed:The CAP 8mg was blended with the ordinary feed Powder 400 g,then the chili feed was prepared well,the concentration of CAP was 10mg/Kg.(2)The experimental animal and grouping: 160 SD rats, were randomly divided into experimental group(Group A) and control group(Group B), 80 rats in each group, rats in Group A were fed with CAP feed(CAP 1mg/kg/d), rats in Group B were fed with normol feed. In order to explore the effects of CAP on visceral mechanical and chemical stimulation in rats at different period, the experimentation was divided into 5 stages, according to the different period, all rats in Group A and Group B were divided into 5 groups, 16 rats in each group, half male and half female. The concrete stage and period: stage I(1 day): Group A1(experimental group) were accessed to water freely, fed with CAP feed,after eating the capsaicin feed,they were ate the normal feed;Group B1(control group) were freely accessed to food and wate; stage II:(3 days): Group A2(experimental group) were accessed to water freely, fedwith CAP feed,after eating the capsaicin feed,they were ate the normal feed;Group B2(control group) were freely accessed to food and wate; stage III(1 week): Group A3(experimental group) were accessed to water freely, fed with CAP feed,after eating the capsaicin feed,they were ate the normal feed;Group B3(control group) were freely accessed to food and wate; stage IV(2 weeks): Group A4(experimental group) were accessed to water freely, fed with CAP feed,after eating the capsaicin feed,they were ate the normal feed;Group B4(control group) were freely accessed to food and wate; stage V(4 weeks): Group A5(experimental group) were accessed to water freely, fed with CAP feed,after eating the capsaicin feed,they were ate the normal feed;Group B5(control group) were freely accessed to food and wate.(3)The visceral sensitivity to mechanical stimulation: the rectal distention test( RDT):inducing rats to exhaust the rectum stool,paraffin oil smeared around the anus,then the air cell of 10 FR catheter was entered the rectum slowly. The remainder catheter was fixed on the tail with adhesive tape. Injecting gas to air cell of catheter with 5ml barrel of the syringe slowly, moreover observing the abdominal withdrawal reflex of rats,until the action of rats reached 4 points of AWR score, end gas injection.(4) The visceral sensitivity to chemical stimulation: intraperitoneal injection of neostigmine with 1ml syringe: neostigmine concentration is 60ug/ml, the dose was 120ug/Kg of each rat. Then observated the AWR action of rats, noted the start time when the behavior of rats reached 3-4 points of AWR score and the duration time of the rats’ behavior.(5)The detection index and method:①General states of the rats.②Theballoon volume of visceral mechanical stimulation in rats:Balloon distention in rats rectal, until the behavior reached 4 points of AWR score, recorded the balloon volume。③The start time when the behavior of rats reached 3-4 points of AWR score and the duration time of the rats’ behavior after intraperitoneal injecting neostigmine,then recorded the start time and duration time. ④The expression of TRPV1 of the stomach, duodenum tissue: detection of TRPV1 with immunohistochemical method。⑤The mucosal barrier of Gastric and duodenal: Rats were sacrificed by dislocation, cuted the mucosal of gastric and duodenal along the greater curvature of the stomach, rinsed the stomach contents with physiological saline。Mucosal morphology was observed by the naked eyes, assessed the gastric, duodenal mucosa using modified Guth standard。3 blocks of tissue taken from greater curvature of the stomach, and 3 blocks of tissue taken from duodenal. All of them had taken to do histopathological examination。Results:(1)General states of the rats: in the course of the experiment, all rats were in good spirits, flexible action, good appetite, smooth fur, normal excretion.(2)The balloon volume(ml): stage I: The balloon volume between Group A1,B1 and Group A2,B2 had no significant differences(P>0.05),but the males in Group A2(2.24±0.13)was significantly less than males in Group B2(2.56±0.21)(P<0.05)。The balloon volume in Group A3( 1.91±0.33) was significantly less than Group B3(2.30±0.30)(P<0.05), further more,the balloon volume in females was significantly less than males in Group A3( 1.68±0.10 vs 2.15±0.30,P<0.05).The balloon volume between Group A4 and Group B4 had nosignificant differences(P>0.05). The balloon volume in Group A5(2.85±0.33)was significantly more than Group B5(2.40±0.53)(P<0.05).(3)The start time when the behavior of rats reached 3-4 points of AWR score and the duration time of the rats’ behavior:①The start time(min): The experimental groups(Group A1,A2,A3,A4) between the control groups(B1,B2,B3,B4) had no significant differences(P>0.05). The start time in Group A5(5.91±1.74) was significantly more than Group B5(4.49±1.53)(P<0.05).②The duration time: The experimental groups(Group A1,A2,A4,A5) between the control groups(B1,B2,B4,B5) had no significant differences(P>0.05). The duration time in Group A3( 6.30±3.16) was significantly more than Group B3(3.13±1.16)(P<0.05)(4)The expression of TRPV1 in gastric and duodenal tissue: ①The PI of TRPV1 in gastric tissue: The PI of TRPV1 in gastric tissue of experimental groups on stage I were significantly more than the control groups(1.97±0.46 vs 1.60±0.25, P<0.05). The PI of TRPV1 in gastric tissue of experimental groups on stage II were significantly more than the control groups(2.14±0.54 vs 1.63±0.51, P<0.05). The PI of TRPV1 in gastric tissue of experimental groups on stage III were significantly more than the control groups(2.16±0.44 vs 1.65±0.43, P<0.05).The experimental groups between the control groups on stage IV and V had no significant differences(P>0.05).②the PI of TRPV1 in duodenal tissue: The PI of TRPV1 in duodenal tissue of experimental groups on stage I were significantly more than the control groups(1.87±0.38 vs 1.60±0.25, P<0.05). the PI of TRPV1 in duodenal tissue: The PI of TRPV1 in duodenal tissue of experimental groups onstage II were significantly more than the control groups(1.80±0.44 vs 1.61±0.31, P<0.05). The experimental groups between the control groups on stage III,IV, V had no significant differences(P>0.05)(5)The mucosal barrier of Gastric and duodenal:all the gastric, duodenal mucosa is smooth, no obvious abnormal observed by the naked eyes,. Pathological observation: all biopsies were intact, villi neatly arranged the organizational structure is complete, and no inflammatory cell infiltration. Conclusion:1.The sensitivity to visceral mechanical stimulation was significantly increased of rats fed with low dose of CAP for 1 weeks, the sensitivity gradually returned to normal for 2 weeks, the sensitivity decreased significantly for 4 weeks. 2. The sensitivity to visceral chemical stimulation was significantly increased of rats fed with low dose of CAP for 1 weeks, the sensitivity decreased significantly for 4 weeks.3. The sensitivity to visceral mechanical stimulation of female rats was more sensitive than male rats.4. There were no significant effects on rat stomach and duodenal mucosal barrier after intaking of low dosage of CAP(1mg/kg/d) from 1 day to 4 weeks.5. Intaking small does of CAP may regulate the expression of TRPV1 in stomach and duodenum tissues of rats,which may have some correlation with the change of sensitivity to visceral mechanical and chemical stimulation.