| Objective To investigate dose-response relationship between botulinum toxin type A and skeletal muscular morphology and strength by injecting botulinum toxin type A in quadriceps femoris of rabbits.Methods Fifteen experimental rabbits(3.0-3.5kg)were randomly divided into five groups:A,B,C,D,and E.Botulinum toxin type A was injected in the right quadriceps femoris in each group with a total dose of 3U(1ml),6U(1ml),12U(1ml),18U(1ml)and 24U(1ml),respectively.And 1ml of normal saline was injected into the same part of the left quadriceps femoris as control.Four weeks after injection,all rabbits receiving:(1)CT scanning and 3D image reconstruction.The volume of quadriceps femoris was measured.(2)Measuring muscular maximum single contractile force and tetanic contractile force using the biological signal acquisition and processing system.(3)Harvest of bilateral quadriceps femoris in whole block,and measuring the wet weight and the volume.Part of the quadriceps femoris of the injection site was stained with hematoxylin-eosin,and observed via microscope.Muscle fiber diameter was observed and measured.The difference of bilateral quadriceps femoris mximum single contractile force,tetanic contractile force,wet weight,volume and muscle fiber diameter were calculated.Test the statistical significance of the difference between different groups and conduct the linear regression analysis with the botulinum toxin type A dose.The GraphPad Prism software was used to draw dose-response curve for muscular maximum single contractile force,tetanic contractile force,wet weight,volume,and the muscle fiber diameter of botulinum toxin type A.Results(1)The maximum single contractile force of right quadriceps femoris of rabbits in groups A,B,C,D and E were 389.4±30.6g,325.9±28.1g,245.1±44.5g,263.1±64.1g,297.7±63.4g,respectively;and 527.8±42.2g,495.8±38.8g,407.1±35.1g,461.6±53.6g,544.2±44.1g on the left,respectively.The differences of the maximum single contractile force between the two sides were statistically significant(p<0.001).The differences were 138.4±11.7g,169.9±18.3g,162.0±14.3g,198.5±21.0g,246.5±20.7g,respectively.The differences between different groups were statistically significant(p=0.016).The linear relationship between the maximum single contractile force of quadriceps femoris difference and the injection dose of botulinum toxin type A was confirmed by the linear regression analysis(y=4.522x+126.086).(2)The tetanic contractile force of right quadriceps femoris of rabbits in groups A,B,C,D and E were 500.6±55.3g,457.5±54.6g,397.0±60.8g,471.5±60.9g,444.8±55.3g,respectively;and 545.7±53.7g,528.7±57.7g,493.7±53.2g,583.6±60.1g,588.0±42.1g on the left,respectively.The differences of tetanic contractile force between the two sides were statistically significant(p<0.001).The differences were 45.1±18.1g,71.2±15.8g,96.7±22.0g,112.1±7.1g,143.2±20.4g,respectively.The differences between different groups were statistically significant(p=0.018).The linear relationship between the tetanic contractile force of quadriceps femoris difference and the injection dose of botulinum toxin type A was confirmed by the linear regression analysis(y=4.326x+39.157).(3)The wet weight of right quadriceps femoris of rabbits in groups A,B,C,D and E were 51.9±5.1g,34.1±6.7g,33.8±3.7g,43.6±5.2 g,28.9±4.2g,respectively;and 57.1±4.3g,49.9±4.2g,51.7±3.9g,62.9±4.9g,50.0±4.5g on the left,respectively.The differences of the wet weight between the two sides were statistically significant(p<0.001).The differences were 5.2±1.8g,15.812.5g,17.9±1.1g,19.3±1.3g,21.1±0.8g,respectively.The differences between different groups were statistically significant(p=0.014).The linear relationship between the wet weight of quadriceps femoris difference and the injection dose of botulinum toxin type A was confirmed by the linear regression analysis(y=0.609x+8.185).(4)The volume of right quadriceps femoris of rabbits in groups A,B,C,D and E were 57.5±3.8ml,38.1±8.5ml,37.8±5.5ml,48.5±6.5ml,32.5±5.4ml,respectively;and 62.0±5.3ml,54.2±6.2ml,56.2±4.8ml,68.4±5.7ml,54.3±4.7ml on the left,respectively.The differences of the volume between the two sides were statistically significant(p<0.001).The differences were 4.5±2.2ml,16.1±2.6ml,18.4±0.7ml,19.9±1.1ml,21.8±1.0ml,respectively.The differences between different groups were statistically significant(p=0.012).The linear relationship between the volume of quadriceps femoris difference and the injection dose of botulinum toxin type A was confirmed by the linear regression analysis(y=0.662x+7.796).(5)The fiber diameter of right quadriceps femoris of rabbits in groups A,B,C,D and E were 32.3±3.3μm,26.8±1.4μm,24.3±1.4μm,22.4±1.7μm,22.5±1.1μm,respectively;and 39.8±2.4μm,41.4±1.7μm,40.0±2.0μm,38.5±2.1μm,40.6±1.1±m on the left,respectively.The differences of the fiber diameter between the two sides were statistically significant(p<0.001).The differences were 7.5±1.0pm,14.6±2.1±m,15.7+1.1μm,16.1±0.7μm,18.1±0.4μm,respectively.The differences between different groups were statistically significant(p=0.043).The linear relationship between the fiber diameter of quadriceps femoris difference and the injection dose of botulinum toxin type A was confirmed by the linear regression analysis(y=0.369x+9.952).Conclusion Injecting of botulinum toxin A lead to muscle atrophy and reduced contractility,with a linear relationship between the degree of change and injection dose. |
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