Mouse (gene-engineered mice) ~Fundamental behavior analysis

 von Frey test: Sensory nerve is briefly tested by von Frey test and hot plate test. Mechanical noniception is assessed by applying von Frey filaments ranging from 0.008 to 1 g to the plantar surface of the hind paw with sufficient force to cause slight bending. The glabrous skin of the hindlimbs of the mice on wire glids is stimulated with several sizes of filaments to determine the threshold for the withdrawal. Testing always begins with the 0.008 g filament and proceeds from small to large monofilaments.

 Three trials are performed on the hind paws of each mouse, and the sources for each hind paw are averaged to yield a mean withdrawal latency.

 Hot plate test: Hot plate test is the other brief way to examine the disorder of sensory system. Sensitivity to noxious heat stimuli is measured with a hot plate test. The animals are placed on a heated plate which is maintained at 52.5 ± 0.5°C by an electronic thermo-regulated water bath. The hot plate is surrounded by a plastic cylinder (height, 20 cm; diameter, 14 cm). The heat threshold is estimated by measuring the interval between the placement of mice onto the hot plate and the initial movement of jumping.

 Each mouse undergoes three trials, and the average score of these three trials is used for statistical analysis. Since this test is for the examination of responses to temperature stimuli, there is often discrepancy from the results of von Frey test as shown in Fig. 1 (Inoue M. et al. 2002).

 Rota-rod test: Motor coordination and balance are examined by the rotarod test. Mice are put on a rotating cylinder, approximately 3 cm diameter, and they need to continuously walk forward to keep from falling off the rotating cylinder. Usually fixed-speed rota-rods are used. After being placed on the rotating cylinder, latency to fall off is measured. Most mice are easily able to maintain balance and stay on the rota-rod for several minnuites at a standard speed, i.e. 5 revolutions per min (rpm). A 1-minute cut-off maximum per trial is often used.

 Recently, accelerating rota-rods are in common use. Mice are placed on the rota-rod with a slow speed, for example, 4 rpm. Rotational speed gradually increases according to a predetermined program, up to a maximum rotational speed, such as 40 rpm. Mice with deficits in motor coordination or balance fall off the rota-rod before the end of the 5-min trial.

 Repeated performance of the rota-rod task over days is quantified as a measure of motor learning.

 Foot printing: Gait disturbance can be briefly examined by foot printing. This test is performed by applying Chromacryl^TM to the foot. Usually red color is on the forelimb and blue color is on the hindlimb.

 After mice walk in a narrow path with paper bottom, shapes, strides and width of foot prints are measured as reported (Sugiura Y. et al. 2005).

 Formalin test: The paw formalin test is used to determine the response to a prolonged noniceptive stimulus generated by localized inflammation (Wheeler-Aceto H. et al. 1990). Mice are gently held and injected subcutaneously with 50 μL of 1.25% formalin in 0.1 M phosphate buffered saline into the dorsal surface of the left hind paw. After formalin injection, mice are observed for licking behavior of their injected hind paw in translucent plastic observation chamber (27x16x13 cm).

 The amount of time spent in licking the injected paws timed continuously every 5 min, starting immediately after the formalin injection up to 60 min post-injection (Handa Y. et al. 2005).