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A Sensitive Period for the Development of Motor Function in Rats: A Microgravity Study

Shannon M. Harding
Shannon M. Harding
, 
Neeraj J. Singh
Neeraj J. Singh
 e 
Kerry D. Walton
Kerry D. Walton
   | 21 lug 2020
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Article Category: Research Article
Pubblicato online: 21 lug 2020
Pagine: 57 - 79
DOI: https://doi.org/10.2478/gsr-2017-0011
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© 2017 Shannon M. Harding et al., published by Sciendo
This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 3.0 License.

Figure 1

Surface righting tactics. The three major tactics are shown: (A) axial righting (seen in mature animals), (B) an intermediate stage tactic called corkscrew righting in which the head and forelimbs first rotate in one direction while the hindlimbs rotate in the opposite direction, and (C) a more immature tactic called U-posture righting in which the animal ventroflexes with quadrupedal extension before rotating its head and body in the same direction. (D) An extreme version of the U-posture righting is shown, in which the animals sat upright was termed L-posture righting.
Surface righting tactics. The three major tactics are shown: (A) axial righting (seen in mature animals), (B) an intermediate stage tactic called corkscrew righting in which the head and forelimbs first rotate in one direction while the hindlimbs rotate in the opposite direction, and (C) a more immature tactic called U-posture righting in which the animal ventroflexes with quadrupedal extension before rotating its head and body in the same direction. (D) An extreme version of the U-posture righting is shown, in which the animals sat upright was termed L-posture righting.

Figure 2

Axial righting on the day of launch and on the first test day after spaceflight in both missions. (A) On the day of landing after the 9-day mission, the control animals (AGC, open bars) used axial righting significantly more often than flight animals (flight, black bars) or animals on the day of launch (basal, gray bars). (B) On the first test day (R2) after the 16-day mission, both groups of control animals (AGC, dark gray bars; VIV, open bars) used axial righting significantly more often than the animals on the day of launch (basal, light gray bars). The VIV animals also used axial righting significantly more often than the flight animals, but there were no differences between the AGC animals and either the flight or the VIV group. Data are the grand means of the mean for each animal for use of axial righting expressed as the percentage of all tactics used, presented as mean ± SEM. * p<0.05, ** p<0.01, *** p<0.001, one-way ANOVA. Basal values were measured only for the 16-day mission, and are presented in both panels for comparison. (The number of animals tested is given in each column.)
Axial righting on the day of launch and on the first test day after spaceflight in both missions. (A) On the day of landing after the 9-day mission, the control animals (AGC, open bars) used axial righting significantly more often than flight animals (flight, black bars) or animals on the day of launch (basal, gray bars). (B) On the first test day (R2) after the 16-day mission, both groups of control animals (AGC, dark gray bars; VIV, open bars) used axial righting significantly more often than the animals on the day of launch (basal, light gray bars). The VIV animals also used axial righting significantly more often than the flight animals, but there were no differences between the AGC animals and either the flight or the VIV group. Data are the grand means of the mean for each animal for use of axial righting expressed as the percentage of all tactics used, presented as mean ± SEM. * p<0.05, ** p<0.01, *** p<0.001, one-way ANOVA. Basal values were measured only for the 16-day mission, and are presented in both panels for comparison. (The number of animals tested is given in each column.)

Figure 3

Use of axial righting over the test period after return from spaceflight. (A) After the 9-day mission, the flight animals used axial righting significantly less often than the control animals between R0 and R6 (AGC, R0–3, n=9; R4–6, n=8; R7, n=3, FLT, R0, n=10; R1–6, n=9; R7, n=8). (B) After the 16-day mission, the flight animals used axial righting significantly less often than either group of control animals throughout the testing period, except on R2 for the AGC group, and on R10 for both control groups (AGC, R2–7, 23, n=7; R10, n=4: FLT, R2–23, n=5: VIV, R2–7, n=6; R3, R4, R23, n=7; R10, n=4). Data are the grand means of the mean for each animal on each day for use of axial righting expressed as the percentage of all tactics used, presented as mean ± SEM. * and + p<0.05, ** and ++ p<0.01, *** and +++ p<0.001, ANOVA. (See Supplementary Tables 1 and 2 for ANOVA and t-test values.)
Use of axial righting over the test period after return from spaceflight. (A) After the 9-day mission, the flight animals used axial righting significantly less often than the control animals between R0 and R6 (AGC, R0–3, n=9; R4–6, n=8; R7, n=3, FLT, R0, n=10; R1–6, n=9; R7, n=8). (B) After the 16-day mission, the flight animals used axial righting significantly less often than either group of control animals throughout the testing period, except on R2 for the AGC group, and on R10 for both control groups (AGC, R2–7, 23, n=7; R10, n=4: FLT, R2–23, n=5: VIV, R2–7, n=6; R3, R4, R23, n=7; R10, n=4). Data are the grand means of the mean for each animal on each day for use of axial righting expressed as the percentage of all tactics used, presented as mean ± SEM. * and + p<0.05, ** and ++ p<0.01, *** and +++ p<0.001, ANOVA. (See Supplementary Tables 1 and 2 for ANOVA and t-test values.)

Figure 4

Surface righting tactics after return from the 9-day (A & C) or 16-day mission (B & D). The data for basal animals were collected only for the 16-day mission, but are presented in all panels for comparison. Axial righting predominated in control animals after landing for both the 9-day (A & B) and 16-day missions. (C) The distribution of righting tactics in flight animals on the day of landing after the 9-day mission was indistinguishable from that of the basal animals. Corkscrew righting predominated in flight animals after the 9-day mission; they used this tactic significantly more often than control animals on R0, R2, and R4. Flight animals also used tactics involving ventroflexion significantly more often than control animals on days R0, R2, and R4. (See Supplementary Table 1.) (D) Righting tactics using ventroflexion predominated in flight animals after the 16-day mission throughout the testing period. Data for P8 (the day before flight for the 16-day mission) are included. Since there were no significant differences between the AGC the VIV control groups in the righting tactics used after the 16-day mission, they were combined into one control group in Figure 4C & D. Data are the grand means of the mean for each animal for each tactic expressed as the percentage of trials in which each tactic was used on each day. (See Supplementary Tables 1 and 2 for ANOVA and t-test values. The number of animals is the same as in Figure 3.)
Surface righting tactics after return from the 9-day (A & C) or 16-day mission (B & D). The data for basal animals were collected only for the 16-day mission, but are presented in all panels for comparison. Axial righting predominated in control animals after landing for both the 9-day (A & B) and 16-day missions. (C) The distribution of righting tactics in flight animals on the day of landing after the 9-day mission was indistinguishable from that of the basal animals. Corkscrew righting predominated in flight animals after the 9-day mission; they used this tactic significantly more often than control animals on R0, R2, and R4. Flight animals also used tactics involving ventroflexion significantly more often than control animals on days R0, R2, and R4. (See Supplementary Table 1.) (D) Righting tactics using ventroflexion predominated in flight animals after the 16-day mission throughout the testing period. Data for P8 (the day before flight for the 16-day mission) are included. Since there were no significant differences between the AGC the VIV control groups in the righting tactics used after the 16-day mission, they were combined into one control group in Figure 4C & D. Data are the grand means of the mean for each animal for each tactic expressed as the percentage of trials in which each tactic was used on each day. (See Supplementary Tables 1 and 2 for ANOVA and t-test values. The number of animals is the same as in Figure 3.)

Figure 5

Distribution of behaviors of flight and control animals when they were first placed in the water after the 16-day mission (expressed as a percentage of trials). (A) On the first day of testing, the animal in all three groups favored trying to leave the water, but the flight animals floated less often than the controls. (B) On R2, all the animals swam when they were placed in the water, but the flight animals still floated less often than the controls. (C) Behaviors were similar in all the groups on R3, R10, and R20. Therefore, the data were pooled. Data are the grand means ± SE of the mean for each animal for each behavior expressed as the percentage of trials in which each behavior was used on each day.
Distribution of behaviors of flight and control animals when they were first placed in the water after the 16-day mission (expressed as a percentage of trials). (A) On the first day of testing, the animal in all three groups favored trying to leave the water, but the flight animals floated less often than the controls. (B) On R2, all the animals swam when they were placed in the water, but the flight animals still floated less often than the controls. (C) Behaviors were similar in all the groups on R3, R10, and R20. Therefore, the data were pooled. Data are the grand means ± SE of the mean for each animal for each behavior expressed as the percentage of trials in which each behavior was used on each day.

Figure 6

Mean stroke duration for each animal. (A) 9-day mission: There was no difference in swimming speed between flight and control animals after landing except on day 5 (p<0.05) (AGC, R0, R2–R5, n=8; R1, n=9; R7, n=6; R8, 14 n=7; R9, n=4: FLT, R0, n=5; R1, 5, n=9; R2, R3, R8, R14, n=7; R4, 9, n=8; R7, n=6) (B) 16-day mission: Flight animals swam faster than control animals after landing. This difference reached significance on days 2, 3, 7, and 16 (see text). There was no significant change in the swimming speed in flight animals over this time. On R23, the control animals swam faster than on R20 (AGC, R1, R2, R7, R20, R23, n=9; R3, 16, n=7: FLT, R1, 16, n=5; R2–R7, n=6; R20, 23, n=4: VIV, R1–R3, n=7; R7, R20, n=5; R16, n=8; R23, n=12) (C) Data from animals in both missions are displayed together with data from the basal animals.
Mean stroke duration for each animal. (A) 9-day mission: There was no difference in swimming speed between flight and control animals after landing except on day 5 (p<0.05) (AGC, R0, R2–R5, n=8; R1, n=9; R7, n=6; R8, 14 n=7; R9, n=4: FLT, R0, n=5; R1, 5, n=9; R2, R3, R8, R14, n=7; R4, 9, n=8; R7, n=6) (B) 16-day mission: Flight animals swam faster than control animals after landing. This difference reached significance on days 2, 3, 7, and 16 (see text). There was no significant change in the swimming speed in flight animals over this time. On R23, the control animals swam faster than on R20 (AGC, R1, R2, R7, R20, R23, n=9; R3, 16, n=7: FLT, R1, 16, n=5; R2–R7, n=6; R20, 23, n=4: VIV, R1–R3, n=7; R7, R20, n=5; R16, n=8; R23, n=12) (C) Data from animals in both missions are displayed together with data from the basal animals.

Figure 7

Weight and rate of weight gain of animals after the 9-day mission. (A) Average weight of each group of animals on the day of landing. (A) Both females and males were included in this mission and are plotted separately. On the day of landing, flight animals of both sexes weighed significantly less than controls. (B) Over the first month after landing, there was no significant difference in the rate of weight gain between flight and control animals (C & D). Weight of female (C) and male (D) animals over three periods post-flight. The only significant difference between the two groups of animals was for female animals from 11 to 15 days. Data are the mean ± SEM. * p<0.05, ** p<0.01, *** p<0.001, t-test.
Weight and rate of weight gain of animals after the 9-day mission. (A) Average weight of each group of animals on the day of landing. (A) Both females and males were included in this mission and are plotted separately. On the day of landing, flight animals of both sexes weighed significantly less than controls. (B) Over the first month after landing, there was no significant difference in the rate of weight gain between flight and control animals (C & D). Weight of female (C) and male (D) animals over three periods post-flight. The only significant difference between the two groups of animals was for female animals from 11 to 15 days. Data are the mean ± SEM. * p<0.05, ** p<0.01, *** p<0.001, t-test.

Figure 8

Weight and rate of weight gain of animals after the 16-day mission. (A) Average body weight of each group of animals on the day of landing. (All were females.) All groups were significantly different from each other on the day of landing, with flight animals weighing the least and the vivarium control animals weighing the most. (B) Rate of weight gain for each group between R0 and R30. The rate of weight gain was greater for the flight animals than either control group. (C) Grand mean of mean body weight each day for animal groups during R0–R10, R11–R14, and R15–R30. The flight group remained significantly lighter than the control animals over the first two periods. By R15–R30, all three groups had similar weights. * p<0.05, ** p<0.01, *** p<0.001, one-way ANOVA.
Weight and rate of weight gain of animals after the 16-day mission. (A) Average body weight of each group of animals on the day of landing. (All were females.) All groups were significantly different from each other on the day of landing, with flight animals weighing the least and the vivarium control animals weighing the most. (B) Rate of weight gain for each group between R0 and R30. The rate of weight gain was greater for the flight animals than either control group. (C) Grand mean of mean body weight each day for animal groups during R0–R10, R11–R14, and R15–R30. The flight group remained significantly lighter than the control animals over the first two periods. By R15–R30, all three groups had similar weights. * p<0.05, ** p<0.01, *** p<0.001, one-way ANOVA.

Significant differences in the righting tactics between flight and control animals after the 16-day mission. (one-way ANOVA and post-hoc test).1

Righting tactic
DayAxialCorkscrewUUCLVentroflexion
R2F(2,15)=3.877F(2,15)= 9.019F(2,15)=21.043
p=0.044p=0.003p=0.0001
FLT-AGCp=0.003p=0.0001
FLT-VIVp=0.014p=0.001p=0.0001
R3F(2,16)=12.566F(2,16)=18.46F(2,16)=4.948F(2,16)=15.68
p=0.001p=0.0001p=0.021p=0.0001
FLT-AGCp=0.0001p=0.002p=0.019p=0.0001
FLT-VIVp=0.001p=0.0001p=0.009p=0.0001
R5F(2,16)=27.176F(2,16)=5.839F(2,16)=5.723F(2,16)=23.897
p=0.0001p=0.012p=0.013p=0.0001
FLT-AGCp=0.0001p=0.006p=0.007p=0.030p=0.0001
FLT-VIVp=0.0001p=0.012p=0.010p=0.043p=0.0001
R7F(2,15)=7.660F(2,15)=9.843
p=0.005p=0.002
FLT-AGCp=0.002p=0.017p=0.033p=0.001
FLT-VIVp=0.005p=0.042p=0.008
R10F(2,10)=5.381F(2,10)=8.331
p=0.026p=0.007
FLT-AGCp=0.016p=0.005
FLT-VIVp=0.024p=0.008
R23F(2,16)=11.626F(2,16)=9.947F(2,16)=17.750
p=0.001p=0.002p=0.0001
FLT-AGCp=0.001p=0.001p=0.0001
FLT-VIVp=0.0001p=0.046p=0.002p=0.046p=0.0001

Mean maximum (most extended) and minimum (most flexed) ankle and knee joint angles during swimming on R0 and R7 for 9-day flight and control animals.

DayGroupAnkle angle (deg)Knee angle (deg)
MaximumMinimumMaximumMinimum
(most extended)(most flexed)(most extended)(most flexed)
R0Flight151±8.8 (3)40±3.8 (3)118±7.1 (3)43±6.7 (3)
Control138±1.6 (5)50±4.5 (5)121±6.5 (5)49±2.1 (5)
R1Flight153±5.7 (3)62±13.1 (3)96±0.5 (3)34±3.7 (3)
Control139±1.8 (3)65± 5.5 (3)106±6.3 (3)47±3.2 (3)
R7Flight134±2.1** (5)53±3.4 (5)121±3.6 (5)68±7.5 (5)
Control123±1.4 (4)54±5.4 (4)122±1.8 (4)77±5.5 (4)
R14Flight133±3.7 (6)52±1.1 (6)116±2.1 (6)63±8.8 (6)
Control124±4.4 (4)57±3.3 (4)123±4.4 (4)73±6.9 (4)

Significant differences in the righting tactics between 9-day mission flight and control animals (two-way t-test).1

DayRighting tactic
AxialCorkscrewUCLVentroflexion
R0t(17)=5.731t(9)=−3.199t(9)= −2.358t(9)= −3.35
p=0.0001p=0.011p=0.043p=0.005
R1t(16)=4.289t(16)= −3.026t(8)= −2.986
p=0.001p=0.008p=0.01
R2t(16)=5.394t(16)= −2.724t(16)= −2.6
p=0.0001p=0.015p=0.019
R3t(16)=3.734t(16)= −3.438
p=0.002p=0.003
R4t(15)=2.745t(15)= −2.155
p=0.015p=0.048
R5t(9.8)=2.557t(8.5)= −3.089
p=00.029p=0.014
R6t(9.2)=2.363
p=0.042

Effect of initial head position on righting strategy after a 16-day spaceflight. Data are the grand mean ± standard error of the mean for each animal for each tactic expressed as the percentage of all tactics used after release from each head position.

GroupHead positionAxial (%)Corkscrew (%)U-posture (%)U and C (%)L-posture (%)Total (%)
Control (n=9)Straight75.4± 9.55.6± 3.916.8±8.500100
Rotated91.3± 4.58.7± 4.5000100
Flight (n=6)Straight14.5± 6.617.5± 4.835.3±8.0211.4±5.931.31±15.3100
Rotated85.6±10.911.1±11.13.3±3.300100

Time required for righting in basal, control, and flight animals after a 16-day spaceflight. Data are the grand means ± standard error of the mean for each animal for each tactic.

PostureGroupMean (ms)Standard error of the mean (ms)n
AxialBasal972687
Control163416
Flight192136
CorkscrewBasal1323747
Control2021010
Flight237274
L-postureBasal——0
Control665144
Flight422382
U-postureBasal899516
Control250146
Flight258204
U and CBasal1213956
Control24083
Flight349784
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