Animal Grip Strength System is the equipment used to evaluate motor function and deficit in rodent models by sensing the peak amount of force an animal applies in grasping specially designed pull bar assemblies. Metering is performed with precision force gauges in such a manner as to retain the peak force applied on a digital display. The values may be either recorded manually or automatically with the included software. Fore and hind limb assessments can be performed concurrently with the dual sensor models or they can be performed in separate trials with the single stand model. Readings may be obtained in pounds, kilograms, or newtons. All values are accurate to within +/- 0.25% of full scale capacity. Force gauges are offered in 0-1Kg and 0-5Kg ranges. Pull bar assemblies are manufactured to suit the species of animal under test. Standard pull bar assemblies are offered for rats and mice.
In practice, the dual sensor model is employed by first allowing the animal to grasp the forelimb pull bar assembly. The animal is then drawn along a straight line leading away from the sensor. The animal will release at some point and the maximum force attained will be stored on the display. In dual sensor models, the animal continues to be moved along until the rear limbs grasp the second pull bar assembly. Again, there will be some point at which the animal releases after which the second sensor will retain the hind limb grip strength. The test for this subject is now complete. The values may be either manually recorded or sent to an attached computer via USB.
A. Remove a mouse from its home cage, gripping the base of the tail between the thumb and the forefinger.
B. Forelimb measurement: Lower the mouse over the grid keeping the torso horizontal and allowing only its forepaws to attach to the grid before any measurements are taken. Gently pull the mouse back by its tail ensuring the mouse grips the top portion of the grid and the torso remains horizontal and record the maximal grip strength value of the mouse that is displayed on the screen. Repeat this procedure twice more to obtain 3 forelimb grip strength measurements.
C. Forelimb and hind limb measurement: Lower the mouse over the grid keeping the torso parallel with the grid and allow both its forepaws and hind paws to attach to the grid before any measurements are taken. Gently pull the mouse back by its tail ensuring the torso remains parallel with the grid and record the maximal grip strength value of the mouse that is displayed on the screen. Repeat this procedure twice more to obtain 3 forelimb/hind limb grip strength measurements.
D. Place the mouse on the balance and record the weight of the mouse.
E. Make a note of any further observations found during the test e.g. failure to grip the grid.
F. Place the mouse back in its home cage.
G. Clean the grid with ethanol (50%) and allow time to dry before testing each cage of mice.
H. Behavioral parameters may be influenced by circadian rhythm therefore testing should be routinely carried out around the same time of day to obtain balanced and valid results. Avoid testing immediately after light-dark transition as behavioral outcome may be affected.
Note. Mice with missing digits (e.g. after toe clipping) should be omitted from this test.