animals : adult male wistar rats ( charles river , yokohama , japan ) were 
 housed under controlled temperature ( 23  1c ) and 12 hr:12 hr light : dark conditions ( lights 
 on at 07:00 hr ) with food and water available ad libitum during the entire 
 experimental period .
all of the procedures were performed in accordance with the guidelines 
 for animal care stipulated by the japanese physiological society and were approved by the 
 ethics committee of miyazaki university .
all efforts were made to minimize animal pain and 
 suffering and the number of animals used .
experimental design : rats were randomly divided into four experimental 
 groups ( n=413/group ) , including a sedentary control group ( control ) , forced exercise group 
 ( treadmill running ) , voluntary exercise group ( wheel running ) and immobilization stress 
 group ( immobilization ) .
all treatments including habituation were performed at the same time 
 ( 11:3012:30 hr for the light period and 20:3021:30 hr for the dark period ) . forced 
 exercise was performed on a motor treadmill ( mk-680 , muromachi - kikai , tokyo , japan ) .
first , 
 the rats were acclimated to the treadmill for five consecutive days at a moderate speed 
 ( 1519 m / min ) for 20 min . on the day of the experiment , they exercised at a faster speed ( 22 
 m / min ) for 20 min . to minimize the degree of physical stress apart from the treadmill 
 exercise itself
the 
 rats allowed to run voluntarily were maintained in a cage with free access to a running 
 wheel ( mk-750pc ; 320 w190 d350 h mm , muromachi - kikai ) for 2 weeks .
after habituation , we 
 limited the period of access to the wheel to only 2 hr ( 11:0013:00 hr for the light period 
 and 19:0021:00 hr for the dark period ) per day for five consecutive days .
the experiment 
 was performed at the same time as habituation , and the sampling was performed when the rats 
 had run approximately 440 m ( the same distance as the forced runners ) .
rats in the 
 immobilization stress group were placed in a cylinder ( diameter : 6 cm , length : 20 cm ) for 20 
 min on the experimental day to impose mental stress . sample collection and measurement of amino acids : sampling of blood and 
 csf was performed immediately after treatment under pentobarbital anesthesia ( 7.0 mg/100 g 
 body weight , injected intraperitoneally ( i.p . ) ) by cardiac and cisternal puncture , 
 respectively .
the 
 plasma was mixed with two volumes of 5% ( w / w ) trichloroacetic acid , centrifuged immediately 
 at 10,000 rpm at 4c for 20 min to remove precipitated protein and then passed through an 
 ultrafree - mc filter ( cat .
ufc5010bk , millipore , billerica , ma , u.s.a . ) , and the 
 concentrations of amino acids were measured with an automatic amino acid analyzer ( l-8800a ; 
 hitachi , tokyo , japan ) .
we focused on the 20 amino acids that form the components of 
 proteins : valine ( val ) , leucine ( leu ) , isoleucine ( ile ) , alanine ( ala ) , methionine ( met ) , 
 proline ( pro ) , tryptophan ( trp ) , phenylalanine ( phe ) , tyrosine ( tyr ) , threonine ( thr ) , 
 glutamine ( gln ) , asparagine ( asn ) , serine ( ser ) , glycine ( gly ) , cysteine ( cys ) , lysine 
 ( lys ) , arginine ( arg ) , histidine ( his ) , aspartic acid ( asp ) and glutamic acid ( glu ) .
briefly , amino acids were separated by cation - exchange chromatography and detected 
 spectrophotometrically after post - column reaction with ninhydrin reagent .
the amino acid 
 concentrations in the csf samples were measured by liquid chromatography - tandem mass 
 spectrometry ( lc / ms / ms ) ( api 4000 , ab sciex , redwood city , ca , u.s.a . ) .
five 
 l of each csf sample was mixed with an equal volume of internal standard 
 solution containing stably labeled amino acids .
subsequently , 10 l of 
 acetonitrile was added , and the samples were mixed with a vortex mixer .
the samples were 
 then centrifuged at 15,000 rpm for 10 min for protein precipitation , and the supernatants 
 were used for subsequent analysis .
to facilitate highly sensitive analysis of amino acids , lc / ms / ms was performed coupled with 
 precolumn derivatization . for the 
 derivatization ,
10 l of supernatant and 30 l of borate 
 buffer ( ph 8.8 ) were mixed , and 10 l of the derivatization reagent was 
 added .
the reaction mixture was diluted and 
 injected into a reverse - phase high - performance liquid chromatography ( hplc ) system ( 20a 
 series ; shimadzu , kyoto , japan ) .
separation of the derivatized amino acids was performed 
 with an inertsil c8 - 3 column ( 2.1  100 mm , 3 m , gl sciences , tokyo , 
 japan ) , and the analytes were detected using triple quadrupole tandem mass spectrometry 
 ( api3000 lc / ms / ms system ; ab / sciex ) in the selected reaction monitoring mode .
the 
 concentrations of plasma glucose , triglycerides , total protein and total cholesterol were 
 measured using a dri - chem 3500v automatic analyzer ( fujifilm , tokyo , japan ) .
statistical analysis : the data are expressed as the mean  standard error 
 of the mean ( sem ) .
the statistical significance of differences among the groups was 
 determined by one - way analysis of variance ( anova ) followed by tukey s test .
there were no significant differences in blood glucose , triglyceride , total protein and 
 total cholesterol concentrations between the control and experimental groups ( n=58/group , 
 fig .
1.concentrations of blood glucose ( mg / dl ; a , e ) , triglycerides 
 ( mg / dl ; b , f ) , total protein ( g / dl ; c , g ) and 
 total cholesterol ( mg / dl ; d , h ) were measured after each experimental 
 treatment in the light ( n=58 ) and dark ( n=57 ) phases .
the data represent the mean  
 standard error of the mean ( sem ) .
c , control ( white bar ) ; t , treadmill running ( black 
 bar ) ; w , wheel running ( gray bar ) ; i , immobilization ( diagonal bar ) . ) .
concentrations of blood glucose ( mg / dl ; a , e ) , triglycerides 
 ( mg / dl ; b , f ) , total protein ( g / dl ; c , g ) and 
 total cholesterol ( mg / dl ; d , h ) were measured after each experimental 
 treatment in the light ( n=58 ) and dark ( n=57 ) phases .
the data represent the mean  
 standard error of the mean ( sem ) .
c , control ( white bar ) ; t , treadmill running ( black 
 bar ) ; w , wheel running ( gray bar ) ; i , immobilization ( diagonal bar ) .
the amino acid profiles and changes in their ratios in each experimental group relative to 
 the control group are shown in figs . 2 and 3fig .
2.alterations in plasma amino acid concentrations after each experimental treatment in 
 the light ( a - c ) and dark ( d - f ) phases .
the concentrations of each amino acid are shown 
 as a percentage ratio relative to the concentrations in the control group ( n=513 ) .
a , 
 d : results for the treadmill - running group ( red lines ) , b , e : wheel - running group 
 ( green lines ) , c , f : immobilization group ( yellow lines ) and control group ( black 
 lines ) .
amino acids indicated in red showed significant differences vs. the control 
 group ( p<0.05 ) .. during the light period ( n=813/group , fig . 

2a2c , table 1table 1.alterations in plasma amino acid concentrations during the light periodamino acids ( mol / l)controltreadmillwheel runningimmobilizationp valuevaline164.3  4.3188.2  10.6166.4  5.1156.6  3.70.0084leucine109.8  4.6152.2  17.3 * 118.8  4.184.7  6.60.0003isoleucine77.5  7.4100.3  5.9 * 72.6  2.692.3  6.4<0.0001alanine341.0  9.9397.5  28.2417.4  17.6315.6  17.50.0027methionine60.5  1.849.2  3.6 * 56.5  2.151.6  2.60.0181proline314.4  16.8341.0  31.8195.4  5.1 * 206.1  15.2*<0.0001tryptophan72.7  1.781.9  4.269.6  2.465.3  2.80.0022phenylalanine59.7  1.476.3  5.8 * 51.3  1.655.6  1.4<0.0001tyrosine84.2  1.7102.6  6.3 * 67.8  2.5 * 72.1  3.1<0.0001threonine247.1  4.6291.7  22.0223.8  10.3213.9  11.30.0012glutamine434.5  14.8375.5  12.5551.6  18.9450.0  18.4<0.0001asparagine38.5  2.222.4  1.8 * 53.4  2.5 * 37.0  1.4<0.0001serine203.7  3.1257.6  20.2 * 240.4  11.4162.1  5.1<0.0001glycine333.7  8.9375.8  19.3389.9  13.5 * 279.7  7.6*<0.0001cysteine10.6  1.428.1  9.36.3  3.10.4  0.40.002lysine349.7  10.1380.3  21.8362.1  13.3292.2  7.7 * 0.0003arginine38.5  2.250.5  9.6147.8  8.8 * 61.1  10.5<0.0001histidine57.2  2.051.1  3.159.5  1.852.5  1.40.0491aspartate10.4  0.739.6  8.0 * 8.9 
1.06.1  0.6<0.0001glutamate162.3  5.7248.6  25.5 * 103.9  7.1 * 133.7  5.2<0.0001the data represent the mean  standard error of the mean ( sem , n=813 ) . * ; 
 p<0.05 vs control , # ; p<0.05 vs treadmill 
 running , $ ; p<0.05 vs wheel running , as identified by tukey s 
 test . ) , many of the plasma levels of amino acids showed significant changes in the 
 three experimental groups relative to the control group . as a result of treadmill running , 
 the levels of 7 amino acids ( leu , ile , phe , tyr , ser , asp and glu ) were significantly 
 elevated , while those of only 2 ( met and asn ) were lower than in the control group ( fig .
although cys levels seemed to rise , there 
 was no significant difference for the large variation . in the wheel - running group ,
the 
 levels of 3 amino acids ( asn , gly and arg ) were increased , and those of 3 other amino acids 
 ( pro , tyr and glu ) were decreased relative to the control group ( fig .
2b ) . in the immobilization stress group , the levels of 3 amino 
 acids ( pro ,
gly and lys ) were decreased , and none were increased ( fig . 2c ) .
furthermore , there were many differences in amino acid 
 levels between the treadmill - running and immobilization groups .
alterations in plasma amino acid concentrations after each experimental treatment in 
 the light ( a - c ) and dark ( d - f ) phases .
the concentrations of each amino acid are shown 
 as a percentage ratio relative to the concentrations in the control group ( n=513 ) .
a , 
 d : results for the treadmill - running group ( red lines ) , b , e : wheel - running group 
 ( green lines ) , c , f : immobilization group ( yellow lines ) and control group ( black 
 lines ) .
amino acids indicated in red showed significant differences vs. the control 
 group ( p<0.05 ) .
the data represent the mean  standard error of the mean ( sem , n=813 ) . * ; 
 p<0.05 vs control , # ; p<0.05 vs treadmill 
 running , $ ; p<0.05 vs wheel running , as identified by tukey s 
 test .
the differences in the levels of individual amino acids between the experimental groups and 
 the control group during the dark period are shown in fig .
2d2f and table 2table 2.alterations in plasma amino acid concentrations during the dark periodamino acids ( mol / l)controltreadmillwheel runningimmobilizationp valuevaline149.6  5.3127.9  4.5159.1  15.9121.0  7.20.0297leucine106.4  4.895.5  5.2114.0  11.184.5  6.00.0412isoleucine62.8  2.556.1  2.969.0  6.150.0  3.30.0131alanine386.8  24.0245.3  11.6 * 320.4 
29.3308.5  12.10.0035methionine57.7  2.949.6  4.258.6  5.857.4  3.90.5722proline199.5  8.8149.2  5.3195.8  24.7172.8  6.80.1038tryptophan61.3  3.159.2  7.469.9  6.574.8  5.30.1513phenylalanine54.3  2.048.9  2.852.7  5.060.8  7.20.4162tyrosine52.4  2.247.5  2.750.0  5.363.6  6.10.0877threonine207.4  7.7162.2  8.8177.3  18.3177.8  8.10.0535glutamine526.4  18.6459.3  23.7508.0  45.2562.6  28.50.2246asparagine37.9  2.127.5  1.734.7  3.939.8  3.20.0809serine220.9  8.0186.9  10.8228.6  23.3190.6  9.50.1273glycine329.5  13.8285.6  17.1310.7  30.1299.2  3.90.4094cysteine4.6  0.74.7  0.81.9  0.35.6  1.20.0267lysine279.5  8.0248.0  14.7262.6  23.5262.4  8.40.5038arginine85.9  15.281.0  24.379.5  12.686.7  4.10.9821histidine58.3  1.449.4  2.055.7  4.958.3  3.30.2798aspartate6.6  1.75.0  0.97.6  1.35.6  0.80.6953glutamate108.1  4.1127.0  6.0127.0  11.5107.6  3.30.0765the data represent the mean  standard error of the mean ( sem , n=512 ) . * ; 
 p<0.05 vs control , $ ; p<0.05 vs wheel running , as 
 identified by tukey s test .
2d ) ; in the wheel - running group and 
 immobilization stress group , there were no significant changes relative to the control group 
 ( fig .
there were no common changes 
 in amino acid levels among the groups , but the levels of 3 amino acids ( val , leu and ile ) 
 were lower in the immobilization stress group than in the wheel - running group .
the data represent the mean  standard error of the mean ( sem , n=512 ) . * ; 
 p<0.05 vs control , $ ; p<0.05 vs wheel running , as 
 identified by tukey s test .
in addition to the concentrations of amino acids in plasma , we examined those in csf and 
 derived the amino acid profiles ( fig . 3fig .
3.alterations in csf amino acid concentrations after each experimental treatment in the 
 light ( a - c ) and dark ( d - f ) phases .
the concentrations of each amino acid are shown as 
 a percentage ratio relative to the concentrations in the sedentary control group 
 ( n=413 ) .
a , d : results for the treadmill - running group ( red lines ) , b , e : 
 wheel - running group ( green lines ) , c , f : immobilization group ( yellow lines ) and 
 control group ( black lines ) . amino acids indicated in red showed significant 
 differences vs. the control group ( p<0.05 ) .
pro , trp , cys , asp and 
 glu were not detectable . ) . because the levels of amino acids are lower in csf than in plasma , some were not 
 detectable in csf ( pro , trp , cys , asp and glu ) . during the light period ( n=813/group , fig .
3a3c , 
 table 3table 3.alterations in csf amino acid concentrations during the light periodamino acids ( mol / l)controltreadmillwheel runningimmobilizationp valuevaline5.7  0.63.6  0.3 * 3.0  0.3 * 4.6  0.50.0013leucine5.3  0.23.7  0.2 * 4.3  0.34.9  0.40.0016isoleucine2.1  0.11.3  0.1 * 1.9  0.11.6  0.2 * 0.0003alanine56.0  2.951.3  2.562.8  2.668.4  6.00.0133methionine5.2  0.42.9  0.4 * 3.9  0.24.7  0.80.0125proline1.3  0.30.3  0.1nd1.0  0.1tryptophan1.9  0.32.1  0.3nd1.7  0.3phenylalanine5.5  0.24.6  0.2 * 3.9  0.1 * 5.3  0.40.0005tyrosine9.7  0.57.9  0.55.1  0.3 * 8.7  0.8<0.0001threonine67.2  2.954.6  1.8 * 54.8  3.664.9  4.70.0132glutamine493.9  18.9473.3  11.4510.1  12.0516.8  28.10.3826asparagine5.9  0.34.7  0.35.1  0.36.6  0.50.0015serine66.8  4.155.1  2.169.3  2.466.2  4.70.0349glycine9.9  1.17.0  0.38.1  0.67.8  1.00.0875cysteine1.6  0.21.5  0.1nd1.3  0.1lysine77.6  2.673.7  1.872.9  3.878.4  3.90.4982arginine35.9  1.532.2  0.528.3  0.8 * 35.1  2.20.008histidine9.8  0.87.8  0.311.4  0.510.9  0.90.0032aspartate1.5  0.31.9  0.2nd1.8  1.0glutamate6.3  1.43.3  0.6nd6.8  2.7the data represent the mean  standard error of the mean ( sem , n=813 ) .
* ; 
 p<0.05 vs control , # ; p<0.05 vs treadmill 
 running , $ ; p<0.05 vs wheel running , as identified by tukey s 
 test . ) , the levels of many amino acids were decreased in the treadmill - running group 
 ( val , leu , ile , met , phe and thr ) , but none showed increased concentrations ( fig .
the levels of 4 
 amino acids ( val , phe , tyr and arg ) were lower than in the control group ( fig .
3b ) , and in the immobilization stress group , the 
 only significant change was a decrease in the concentration of ile ( fig .
3c ) . a change in the level of ile was detected in both the 
 treadmill - running and immobilization stress groups .
alterations in csf amino acid concentrations after each experimental treatment in the 
 light ( a - c ) and dark ( d - f ) phases .
the concentrations of each amino acid are shown as 
 a percentage ratio relative to the concentrations in the sedentary control group 
 ( n=413 ) .
a , d : results for the treadmill - running group ( red lines ) , b , e : 
 wheel - running group ( green lines ) , c , f : immobilization group ( yellow lines ) and 
 control group ( black lines ) . amino acids indicated in red showed significant 
 differences vs. the control group ( p<0.05 ) .
the data represent the mean  standard error of the mean ( sem , n=813 ) .
* ; 
 p<0.05 vs control , # ; p<0.05 vs treadmill 
 running , $ ; p<0.05 vs wheel running , as identified by tukey s 
 test . during the dark period ( n=412/group , fig . 
 3d3f , table 4table 4.alterations in csf amino acid concentrations during the dark periodamino acids ( mol / l)controltreadmillwheel runningimmobilizationp valuevaline2.7  0.12.2  0.23.0  0.12.8  0.20.0421leucine4.1  0.23.5  0.24.4  0.24.2  0.40.0526isoleucine1.8  0.11.7  0.12.0  0.12.0  0.20.3907alanine57.1  2.253.1  0.459.0  1.857.8  3.70.4347methionine2.9  0.33.3  0.63.4  0.33.7  0.20.4238prolinendndndndtryptophanndndndndphenylalanine4.3  0.24.7  0.24.2  0.14.9  0.20.1255tyrosine4.3  0.35.1  0.64.4  0.36.7  0.4 * 0.0022threonine52.0  1.551.8
 2.645.5  1.660.3  2.9 * 0.0011glutamine455.5  13.3512.8  22.2478.0  15.6545.8  7.8 * 0.0066asparagine5.0  0.24.8  0.25.2  0.45.8  0.50.242serine62.1  1.964.8  2.875.7  1.3 * 67.3  1.40.0002glycine7.4  0.58.4  0.57.6  0.56.7  0.60.4248cysteinendndndndlysine63.9  2.473.0  3.664.3  1.772.6  7.30.1176arginine28.5  0.930.4  0.627.8  1.230.2  1.60.3598histidine11.6  0.613.2  0.311.3 
0.311.4  0.50.1327aspartatendndndndglutamatendndndndthe data represent the mean  standard error of the mean ( sem , n=412 ) . * ; 
 p<0.05 vs control , # ; p<0.05 vs treadmill 
 running , $ ; p<0.05 vs wheel running , as identified by tukey s 
 test . )
, few changes were evident among the experimental groups when compared with 
 the light period .
3e ) , and immobilization stress led to increased 
 levels of tyr , thr and gln ( fig .
the data represent the mean  standard error of the mean ( sem , n=412 ) . * ; 
 p<0.05 vs control , # ; p<0.05 vs treadmill 
 running , $ ; p<0.05 vs wheel running , as identified by tukey s 
 test .
to our knowledge , this is the first reported study to have investigated and demonstrated 
 changes in the levels of individual amino acids in both plasma and csf after different types 
 of short - term exercise .
the concentrations of plasma glucose , total protein , triglycerides and total cholesterol 
 were not significantly changed by these types of exercise , but obvious changes were evident 
 in the amino acid profiles .
it is well known that glucose and lipid are used as an energy 
 source for high - intensity or prolonged exercise , 
 and the exercise used in this study was mild .
however , under such conditions , it was 
 interesting that the plasma levels of amino acids tended to alter rather readily . a greater 
 number of amino acids showed a change in their levels during the light period , and the 
 degree of change differed among the groups .
the basal levels of many amino acids were higher 
 during the dark period ( active phase ) than during the light period ( resting phase ) .
although 
 the reason for the greater change in amino acid levels resulting from exercise during the 
 light period compared with the dark period is unclear , sudden exercise during the light 
 period ( resting period ) might elicit an abrupt change in metabolism by nervous control , such 
 as from parasympathetic regulation in the resting phase to sympathetic regulation . 

generally , it has been shown that physical exercise causes amino acid imbalance by promoting 
 proteolysis relative to protein synthesis in skeletal muscle , which leads to a decrease in 
 plasma bcaa levels [ 1 , 5 ] .
conversely , in the case of short - term forced exercise , it has been reported 
 that plasma bcaa levels increase . in the present 
 study also , treadmill running led to a significant increase of both leu and ile . on the 
 other hand ,
wheel - running exercise elicited no significant change in bcaa levels , suggesting 
 that the physical or mental impact of forced exercise on the body differs significantly from 
 that of voluntary exercise .
in addition , among the amino acids involved in the urea cycle , asp and arg were 
 specifically increased by treadmill running and wheel running , respectively .
although it is thought that both types 
 of exercise activate the urea cycle , there may be a difference in the strength and speed of 
 the reaction . because the concentrations of amino acids in the csf were very low in comparison to those 
 in the plasma , some amino acids were undetectable .
amino acid metabolism in the brain is 
 essential for the construction and regeneration of cell membranes and organelles and plays 
 an important role in the synthesis of neurotransmitters , neuropeptide proteins and enzymes . 

although the absolute levels of amino acids in csf may differ from those in plasma , it has 
 been generally considered that the amino acid profiles in the two compartments are 
 correlated .
plasma amino acids 
 are transferred to brain across the blood - brain barrier ( bbb ) through the various amino acid 
 transporters .
furthermore , the observation that the concentrations of amino acids in the csf were very 
 lower than those in the plasma suggests that the mechanism of maintenance of the amino acid 
 concentrations in csf may be much more strict . during the light period ,
the most characteristic change was a decrease of all amino acids 
 in the csf .
the observation that treadmill running during the light period led to an 
 increase of bcaa levels in plasma with a converse decrease of those in csf was of particular 
 interest .
although the reason for this decrease is unclear , it is known that exercise 
 increases the levels of glutamate and glutamine in the brain .
large neutral amino acids in plasma , including bcaa , are transferred 
 to the brain by counter - transport with glutamine .
especially , transamination of bcaa is a major source of nh2 for 
 synthesis of glutamate .
furthermore , when we compared the profiles of plasma amino acids during the light period 
 between the treadmill - running , wheel - running and immobilization stress groups , they all 
 differed from each other .
that is , many different kinds of amino acids were increased by 
 treadmill running and wheel running , whereas most were decreased by immobilization .
it can 
 be speculated that proteolysis ( catabolism ) caused by physical exercise in compartments , 
 such as skeletal muscle , would lead to an increased flow of free amino acids to the liver 
 via the bloodstream for use in gluconeogenesis or lipid metabolism .
however , in the case of 
 immobilization stress , it can be speculated that amino acids are mobilized from the 
 available pool and that anabolism is promoted in the brain and other areas . in both the 
 treadmill - running and wheel - running groups ,
on the other hand , the levels of different kinds 
 of amino acids were changed . as a result of treadmill running ,
leu , ile , phe , tyr , ser , asp 
 and glu were increased , whereas wheel running increased the levels of asn , gly and arg . 

these results suggest that even if the running distance is the same , forced running and 
 voluntary running may influence amino acid metabolism in different ways .
treadmill running 
 may induce greater physical fatigue than wheel running , because the change in the amino acid 
 profile induced by the former resembles that induced by long - term exercise .
the amino acid profile shown in the present study might be effective to compare the general 
 change of amino acid , and there may be possibility that amino acid , such as asp and cys , 
 having very low basal levels may be misunderstood as large change by variation of each 
 value
. further improvement of profiling of amino acid may be necessary . in the present study
, we showed that different types of exercise ( forced and voluntary ) 
 cause different patterns of change in the levels of amino acids in plasma and csf . 

furthermore , the amino acid profile resulting from treadmill running differed from that 
 induced by immobilization stress .
these results suggest that the changes in amino acid 
 levels induced by treadmill running are not solely attributable to the mental stress 
 associated with forced exercise .
rather , they may be due to the differences in interaction 
 between physical and mental fatigue .
moreover , no correlation was found between amino acid 
 levels in plasma and those in csf .
these results suggest that the levels of amino acids in 
 csf are not always affected by a change in peripheral plasma levels . further investigations 
 will be necessary to clarify the factors responsible for imbalances in amino acid levels , 
 and how amino acid homeostasis is maintained .
 it has been suspected that in comparison with glucose or fatty acids , the levels of amino 
 acids may readily change with different forms of exercise . in the present study , we 
 measured the concentrations of amino acids , glucose , triglycerides , total protein and 
 total cholesterol in the blood and/or cerebrospinal fluid ( csf ) of rats subjected to 
 forced running exercise on a treadmill , and voluntary running exercise using a wheel , with 
 a constant running distance of 440 m. rats that performed no running and rats subjected to 
 immobilization stress were used as controls . 
 we observed a few significant changes in the 
 levels of plasma glucose , triglycerides , total protein and total cholesterol in all 
 groups . whereas , plasma amino acid levels were significantly changed by exercise and 
 stress , especially during the light period . 
 the plasma levels of many amino acids were 
 specifically increased by forced running ; some were decreased by immobilization stress . 
 
 few amino acids showed similar changes in their levels as a result of voluntary running . 
 
 in addition , there was a significant difference in the degree of amino acid imbalance 
 between blood and csf . 
 these results provide the first information on changes in levels of 
 amino acids in plasma and csf resulting from forced and voluntary exercises . 
MATERIALS AND METHODS
RESULTS
DISCUSSION