4.6. Grip strength test

The grip strength test was performed as described (Deacon, 2013) with slight modifications. Briefly, the apparatus consisted of four weighted chains attached to a fine mesh for mice to grip onto. Mice were suspended by the mid-base of their tail and slowly brought down to the bench to grasp the wire mesh and chains. Mice were required to pick up the mesh and weights and to be fully suspended off the table for 3 s to achieve a passing score for that weight level. Mice from each cage were tested one at a time on picking up the fine wire mesh (WM) without added weight, WM with one chain link, WM with two chain links, WM with three chain links, and WM with four chain links, weighing 18.8 g, 39.3 g, 59.8 g, 80.8 g and 115.8 g respectively. Once a mouse passed a weight level the other mice from that cage were tested on that weight level, and then all mice were tested on the next weight level. A mouse was allowed three trials to hold the weight successfully; failure to hold the weight successfully resulted in the previous weight level being assigned as its outcome score. Score (Max chain links X 3 s) Max seconds on failed weight level. Example: A mouse successfully holding two-weight chains but only holding the three weight chains for 2 s. Score = (2 chains × 3 s) + 2 s = 8.