Experimental study of the relationship between chronic stress and somatic symptoms

Objective To study the possible effects of chronic stress on somatic symtoms through observing the gastric motility of rats under chronic stress. Methods Seventy-five Sprague Dawley(SD) male rats were randomly divided into two groups as chronic stress group(n=50) and normal control(n=25).The chronic stress group underwent water immersion restraint stress 1 hour everyday for 21 consecutive days,and the raising conditions were similar for two groups.Observation index:(1) The changes of bodyweight and food intake of the rats after chronic stress;(2) Stool obscure blood test of the rats;(3) The contents of monoamine transmitters and related metabolites(5-HT,5-HIAA,NA,MHPG,DA and HVA)in the cerebrospinal fluid after chronic stress;(4) Evaluation of cognitive ability by water maze test;(5) The measurement of the velocity of gastric emptying by using phenol red test. Results(1) Before the chronic stress,there was no significant difference in the body weight(g)(258.27±10.72 vs 260.97±10.29,P0.05) and the food intake(g)(26.63±0.82 vs 25.99± 0.43,P0.05) between the two groups;after the chronic stress,the body weight of the stress group was significantly lower than the control(289.72±9.84 vs 392.48±10.81,P0.001),and the food intake was significantly smaller than that of the control(19.72±1.99 vs 29.22±1.45,P0.01);(2) The stool obscure blood test of the two groups was negative;(3) Comparing with the control,the contents of 5-HT and 5-HIAA of the stress group were significantly lower(14.80±2.50 vs 34.5±2.50,P0.001 and 68.36±5.34 vs 114.15±6.13 respectively,P0.001),while the contents of DA,NA and HVA were higher,but with no statistical significance;(4) There was a significant difference in time consumption for the rats to swim out of the maze between the two groups in water maze test(the first day: 57.2±12.01 vs 47.68±10.13,P0.01;the second day: 58.44±14.13 vs 46.88±10.48,P0.01),but there was no significant difference in the error frequency between the two groups in water maze test(the first day:6.22±3.26 vs 5.88±3.38,P=0.403,the second day: 6.4±3.31 vs 5.72±3.37,P=0.304);(5) The gastric residual phenol red rate of the stress group was significantly higher than that of the control(33.52±10.00 vs 21.66±6.22,P0.005). Conclusions Chronic stress can cause a decrease gastric motility of rat without disorders of cognitive function.