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大鼠接受不同運動刺激后高嶺土攝取量分析

康文博 董玉琳 張富興 李金蓮 李云慶

摘 要:

目的分析選擇不同運動方式作用于大鼠的前庭感受器后,誘導高嶺土攝取量變化作為運動病指標的有效性。方法大鼠隨機分成5組,其中3組分別經過沿耳間軸(IA)、頭尾軸(AP)進行的直線加速運動和雙軸旋轉運動(DR)刺激,另2組用于對照組。實驗時記錄刺激前、后各3d的高嶺土攝取量,并對數據做統計學分析。結果本研究觀察到:1)進行IA、AP和DR刺激后,上述各組分別有25%、17%和58%的大鼠在刺激后3d高嶺土攝取量較之刺激前3d的平均增加1g以上;2)與有些報道不同,本研究中刺激后高嶺土攝取量的增加持續1d以上。結論3種運動刺激模式均可作為選擇性刺激前庭感受器官后誘導大鼠增加攝取高嶺土的方法,其中雙軸旋轉運動刺激最為有效。

作者單位:第四軍醫大學人體解剖學教研室暨梁銶琚腦研究中心,陜西西安 710032

【摘要】 分析選擇不同運動方式作用于大鼠的前庭感受器后,誘導高嶺土攝取量變化作為運動病指標的有效性。方法 大鼠隨機分成5組,其中3組分別經過沿耳間軸(ia)、頭尾軸(ap)進行的直線加速運動和雙軸旋轉運動(dr)刺激,另2組用于對照組。實驗時記錄刺激前、后各3 d的高嶺土攝取量,并對數據做統計學分析。結果 本研究觀察到:1)進行ia、ap和dr刺激后,上述各組分別有25%、17%和58%的大鼠在刺激后3 d高嶺土攝取量較之刺激前3 d的平均增加1 g以上;2)與有些報道不同,本研究中刺激后高嶺土攝取量的增加持續1 d以上。結論 3種運動刺激模式均可作為選擇性刺激前庭感受器官后誘導大鼠增加攝取高嶺土的方法,其中雙軸旋轉運動刺激最為有效。

【關鍵詞】 異食癖 運動 前庭系統 運動病


  pica is a behaviour of eating nonQnutritive substance, such as rat eats kaolin after subjected to particular motion stimulation. eating kaolin has been putatively considered by many researchers to be an equivalent of emetic response in animals?1Q4?. it is, therefore, widely used as a surrogate for development of motion sickness (ms) in rats without emetic response. so far, based on the neural mismatchhypothesis for ms, increase of kaolin intake in rat under various motion stimulations has been designed to evaluate ms?1Q2, 5?. most researchers of the previous work assumed that rat didn’t eat kaolin before suffering from motion stimulation, and allowed rat enclosed in a larger container to move freely as motion stimulation, to cause neural mismatch of proprioceptive, visual and vestibular signals?1, 5?.

  neural information related to pathogenesis of ms has been speculated to involve proprioceptive, visual and vestibular signals?2,6?. according to this viewpoint, ms will occur when these signals mismatch with what the organisms have stored in the brain on the basis of previous experience. vestibular system, which can send into brain signals about the motion and position of the head, is of considerable importance in genesis of ms under many circumstances?1Q2?. car sickness may owe more to otolith organ stimulation, while active head movement which stimulates semicircular canals can be a main inducement for other ms cases. in addition to the understanding of ms of rat following motion stimulation, kaolin intake increase of rat can serve as a good index for investigating vestibular function?7?.

  in order to evaluate more accurately the vestibular contribution to inducing kaolin intake changes in rat, and to try to find a stimulation pattern which is more effective in this respect, we used three types of motion stimulation patterns in this study. our experiment was designed as the motions primarily stimulated otolith organ or semicircular canals in the inner ear, respectively.

  materials and methods

  animals sixty spragueQdawley rats (140∼160 g),were divided into 5 groups with sexes oneQtoQone. all the animals were caged separately for oneQweek of habituation in an animal room with natural dark and light cycle. during this period, the rats had free access to water, normal food and kaolin. kaolin was prepared by mixing hydrated aluminium silicate with gum arabic (100?1, shanghai wuyi chemical), adding distilled water to form paste which was squeezed out through a syringe to form columns similar in size and shape to normal food. the resulting kaolin columns were then dried in an electric dryer.

  stimulation patterns three different types of motion stimulation patterns were employed in the experiments. each rat was enclosed in a customized plastic cylindrical restrained cage (15 cm long and 5 cm in diameter) while stimulated, and the eyes were blindfolded with a coneQshaped device which simultaneously restrained the snout of rat. thus, the head of the rat was relatively fixed during the stimulation phase. the first group of rats (ia) was subjected to a 6Qhour linear acceleration in a sinusoidal pattern. the restrained cage was so positioned on a motorQdriven sled that the interaural axis of the animal head paralleled the motion track. the sled moved horizontally to and fro with frequency of 1.2 hz, amplitude of 0.12 m, and maximum velocity of 1.12 m/s and 5.2 m/s2 acceleration was resulted. this value was derived from the equations:s =12 at2 and t=14 f, where s is the amplitude, a is the acceleration, t is one quarter time of one periodic sinusoidal stimulation, and f is the frequency.

  kang wenQbo,et al.analysis of kaolin intake in rats subjected to different motion stimulations[dm)?in the 2nd group (ap), rats experienced motion in the same way as the first group except the motion were oriented with the long body axis (anteQposterior axis) paralleling the motion track.

  the third group (dr) of animals experienced a double rotation stimulation, which was implemented with an equipment comprised of two horizontal rotating discs, 80 cm and 30 cm in diameter, respectively. the small disc is installed on the big one with their axes 24 cm off from each other. during the 1 h stimulation the big disc rotated at a velocity of 150 ° /s, 15 s clockwise alternating with 15 s counterQclockwise, and the small one rotated in a clockwise direction at a velocity of 444 ° /s with reference to the big disc. the rats were positioned on the small disc in an offQaxis manner, with the heads directed towards the axis. therefore, the rats experienced complex angular acceleration (38 °/s2) on a regular basis, and the changing centrifugal forces from both discs.  

  the 4th and 5th groups were used as control. after enclosed in the restrained cages, rats were placed right alongside of the stimulators for sinusoidal linear acceleration and double rotation, respectively, with the same time duration as the experimental rats. 

  kaolin intake record and data analysis daily kaolin intake was monitored 3 d before and 3 d after stimulation. on the 4th day, the rats were stimulated. in this period, kaolin weighed to the accuracy of 0.01 g was provided for each rat at a set time every day, and 22 h later it was taken out and the scattered crumbs collected too. the total kaolin was again dried and weighed. the amount of kaolin consumed in a single day was obtained by subtraction the amount of kaolin after 22 h from that originally served. the total kaolin intake in 3 d either before or after stimulation (preQand postQstimulaion, respectively) was represented by x±s(standard error) for each group. for convenient sake, we defined delta (△ ) = total kaolin intake in 3Qday period before stimulation subtracted from that in the same duration postQstimulation. for temporal change of kaolin intake analysis, the mean intake per day was calculated.

  results

  for the individual rat in each group, we monitored and calculated kaolin intake of everyday. it was showed that mean kaolin intake was increased by various motion stimulations for each group (table 1). this may imply, based on the generally accepted view, that the animals suffered from ms. however, we observed that 5, 3 and 2 rats, in ia, ap and dr groups respectively, did not show kaolin increased. when pica, net kaolin intake, is used as index there has not been established a differential standard to be generally accepted for evaluating ms rats. we analyzed the data in 3 ways for all the groups, employing differential stringential stringent standards. in addition to analysing the data with all the animals included in each group, rats with either △>0 or △>1 within each individual group were selected for further analysis in a similar way (table 1,2). the current data demonstrated that all the 3 experimental groups displayed an increase of kaolin intake in the 3Qday phase following stimulation comparing with that before stimulation, but tQtest shows that there is significant difference in dr, and in ia when only in the cases of △>0 (table 1).

  the percentages of rats which showed kaolin increase following particular motion stimulation are different (table 3). in ia group, 58% of the rats had kaolin intake increase of more than 0 g and 25% more than 1 g postQstimulation, respectively; while ap group showed a 75% and 17% for the same standard. in dr group, the corresponding percentages are 83% and 58%, respectively. although dr group showed the highest percentage of rats with kaolin intake increase following stimulation, chiQsquare test showed no significant difference (table 3).

  comparing with some reports which claimed rat ate no kaolin in natural condition?1, 8?, we observed that some rats ate kaolin during habituation period, with daily intake ranging from 0.01 to 1.78 g. the discrepancy between our findings and that of others may be due to the different strains (wistar vs. sprague dawley) and age of rats used or different experimental patterns?1Q3, 5, 8?.  

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