Mice are increasingly being used in behavioral neuroscience, largely replacing rats as the behaviorist's animal of choice. Before aspects of behavior such as emotionality or cognition can be assessed, however, it is vital to determine whether the motor capabilities of e.g. a mutant or lesioned mouse allow such an assessment. Performance on a maze task requiring strength and coordination, such as the Morris water maze, might well be impaired in a mouse by motor, rather than cognitive, impairments, so it is essential to selectively dissect the latter from the former. For example, sensorimotor impairments caused by NMDA antagonists have been shown to impair water maze performance(2). Motor coordination has traditionally been assessed in mice and rats by the rotarod test, in which the animal is placed on a horizontal rod that rotates about its long axis; the animal must walk forwards to remain upright and not fall off. Both set speed and accelerating versions of the rotarod are available. The other three tests described in this article (horizontal bar, static rods and parallel bars) all measure coordination on static apparatus. The horizontal bar also requires strength for adequate performance, particularly of the forelimbs as the mouse initially grips the bar just with the front paws. Adult rats do not perform well on tests such as the static rods and parallel bars (personal observations); they appear less well coordinated than mice. I have only tested male rats, however, and male mice seem generally less well coordinated than females. Mice appear to have a higher strength:weight ratio than rats; the Latin name, Mus musculus, seems entirely appropriate. The rotarod, the variations of the foot fault test(12) or the Catwalk (Noldus)(15) apparatus are generally used to assess motor coordination in rats.
Objective: Measurement of forelimb strength and coordination by observing mice gripping and traversing a suspended horizontal bar
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Bring mice to the experimental room before testing to ensure they are fully awake
Note: General rule for all tests
“For all tests, bring mice to the experimental room 5-20 min before testing, to ensure they are fully awake”
Hold mouse by tail and place it on bench in front of apparatus. Slide mouse quickly backwards about 20 cm to align it perpendicular to bar
Note: This alignment is critical for proper test execution
“Holding the mouse by the tail, place it on the bench in front of the apparatus, slide it quickly backwards about 20 cm (this aligns it perpendicular to the bar)”
Rapidly raise mouse and let it grasp horizontal bar at central point with forepaws only. Release tail simultaneously while starting stopclock
Note: Timing begins immediately upon release. Some mice grip better if tail is released suddenly
“rapidly raise it and let it grasp the horizontal bar at the central point with its forepaws only, and release the tail, simultaneously starting the stopclock”
Observe mouse performance until either: (1) mouse falls from bar before reaching end column, or (2) one forepaw touches a column
Note: Maximum test time (cut-off time) is 30 sec. Record time of fall or contact with column
“The criterion point is either a fall from the bar before the mouse reaches one of the end columns of the bar, or the time till one forepaw touches a column. Maximum test time (cut-off time) is 30 sec”
If mouse fails to grasp bar properly on first attempt and this appears due to experimenter technique rather than mouse ability, allow retry after brief rest
Note: Do not record this fall. If mouse falls before 5 sec and not due to poor placing, repeat up to three times total to attempt to get >5 sec score
“If the mouse fails to grasp the bar properly first time and this appears to be attributable to the experimenter's technique, rather than the mouse, try again (after a brief rest while another one or two mice are tested) and do not record this fall”
Score performance based on time intervals: 1-5 sec = 1 point; 6-10 sec = 2 points; 11-20 sec = 3 points; 21-30 sec = 4 points; after 30 sec or forepaw on support = 5 points
Note: Take best score as datum. Mice that repeatedly fail to support themselves for >5 sec score only 1
“Falling between 1-5 sec = 1; Falling between 6-10 sec = 2; Falling between 11-20 sec = 3; Falling between 21-30 sec = 4; Falling after 30 sec = 5; Placing one forepaw on a bar support without falling = 5”
If using triple-bar version and mouse scores 5 on 2mm bar, test on thicker bars (4mm and 6mm) after brief rest period
Note: Scoring system is same for all bar diameters. Final score is cumulated total across all bars tested
“If the triple-bar version is being used, if the mouse scores 5 on this first 2 mm bar it can then be tested on thicker bars, after a brief rest period while another one or two mice are tested. The final score is the cumulated total”
Set rotarod with start speed of 4 rpm and acceleration rate of 20 rpm/min. Maximum speed is 40 rpm
Note: These settings are critical for proper test execution
“Set the rotarod with a start speed of 4 rpm, acceleration rate 20 rpm/min”
Hold mouse by tail and place on rotating rod facing away from direction of rotation. Bring mouse up towards rod at 45° below horizontal angle. Quickly release when almost touching rod, just forward of and above rod's top dead center
Note: Attempting to lower from above results in mouse spreading hind legs and grasping flange edges
“Holding the mouse by the tail, and place it on the rotating rod, facing away from the direction of rotation so it has to walk forward to stay upright. This is easiest to do if the mouse is brought up towards the rod at an angle of 45° below horizontal”
Hold mouse in one hand and lower it onto thin dowel (10-15mm) parallel to long axis. Angle dowel with mouse's head downwards about 30° to give more time to grip rotarod. Lower mouse and dowel between flanges, then pull dowel downwards away from mouse
Note: This technique is probably easier and more reliable than method 1
“A (probably easier and more reliable) technique is to use a thin (10-15 mm) dowel. Holding the mouse in one hand, lower it on to the dowel, parallel to the long axis. The dowel is angled with the mouse's head downwards about 30°”
At 10 seconds after placing mouse on rod, start acceleration (only if mouse is facing forward; if not, wait until it does face forward before starting acceleration)
Note: Timing of acceleration initiation is critical
“At 10 sec after placing the mouse on the rod, start acceleration (as long as the mouse is facing forward: if not, wait till it does face forward before starting acceleration)”
Note the speed at which mouse falls off. If falls before 10 sec, note time of fall and try again up to three times total, recording speed at first fall after 10 sec point
Note: Falls before 5 sec due to poor experimenter placement should not be recorded
“note the speed at which the mouse falls off. If it falls off before 10 sec, note the time of fall and try again, up to three times in total, recording the speed at the first fall after the 10 sec point. However, falls before 5 sec which are due to poor placing by the experimenter should not be recorded”
Calculate mean speed at fall across trials. If mouse fails to grip in 10 sec three times, assign score of 4 rpm
Note: Using mean rather than maximum speed corrects for extra practice during failed runs
“The mean speed at fall is the datum; rather than using the maximum speed, this corrects for the extra practice the mouse receives during the failed runs. If a mouse fails to grip in 10 sec three times assign it a score of 4 rpm”
Place mouse at far end of widest rod (35mm diameter). Position nose tip one head's length from the end
Note: Start with widest rod and progress to narrower rods
“Place the mouse at the far end of the widest rod (nose tip one head's length from the end is ideal)”
Measure time taken for mouse to orientate 180° from starting position towards the shelf
Note: If mouse turns upside down and clings below rod, assign maximum orientation score of 120 sec and do not test on smaller rods
“Take two measures: orientation time (time taken to orientate 180° from the starting position towards the shelf) and transit time (the time taken to travel to the shelf end”
Measure time taken to travel to shelf end (nose beyond 10 cm mark from shelf end of rod)
Note: If mouse falls or reaches maximum test time of 120 sec, do not test on smaller rods
“transit time (the time taken to travel to the shelf end (nose beyond the 10 cm mark from the shelf end of the rod)”
If mouse turns upside down and clings below rod, note this event. For statistical purposes, assign maximum score of 120 sec for that rod and subsequent rods
Note: Mouse must stay upright for successful transit and orientation
“If it turns upside down and clings below the rod, arbitrarily assign it (for statistical purposes) the maximum orientation score of 120 sec. Do not test it on smaller rods”
After testing on one rod, return mouse to home cage to rest. Then place on next smaller size rod and test in same way
Note: Stop testing if mouse falls off rod after being on it for more than 5 sec
“After testing on one rod return the mouse to the home cage to rest while you test another mouse. Then place it on the next smaller size rod and test it in the same way again”
If mouse falls off in less than 5 sec, replace it and allow another attempt (as falling within 5 sec could be due to faulty placing). Allow maximum of three trials and use best result
Note: Only applies to falls within 5 seconds
“If it fell off in less than 5 sec replace it and allow another attempt (as falling within 5 sec could be due to faulty placing by the experimenter), for a maximum of three trials, and use the best result”
Place mouse in center of two bars with its longitudinal axis perpendicular to that of the bars. Both front paws should be on one bar, both hind paws on the other bar
Note: This positioning is novel for mice and has not been encountered in home cage enrichment
“Place the mouse in the center of the two bars with its longitudinal axis perpendicular to that of the bars; both front paws should be on one bar, both hind paws on the other bar”
Measure time taken until mouse orients 90° to start position
Note: Similar scoring to static rods test
“Take two measures: the time taken until the mouse orients 90° to the start position, and the time until it subsequently reaches one of the end supports”
Measure time until mouse reaches one of the end supports
Note: Mouse must remain upright for successful performance
“the time until it subsequently reaches one of the end supports”
If mouse turns upside down, note this event. Orientation and transit must be achieved while upright
Note: Similar handling as static rods test
“If the mouse turns upside down, also note this event. As for the static rods test, orientation and transit must be a”
Return mouse to home cage after each motor test to allow recovery of muscular strength and return to normal levels of arousal
Note: General rule for all tests
“As a general rule, to allow recovery of muscular strength and a return to normal levels of arousal, rest the mice by a return to the home cage after each motor test”
Clean and sterilize equipment between each mouse tested
Note: Critical for hygiene and preventing disease transmission
“Also, be sure to clean and sterilize the equipment between each mouse tested”
Hundreds of mice tested at Oxford, including normal and genetically modified animals