According to medical developments survivors from brain disorders and traumas are increasing and ironically rehabilitation is more needed. Brain neuronal damages by cerebral infarction, traffic accidental traumas and so on cause impairments in motor function, conversation, and so on and higher brain dysfunctions such as deficits of affection, learning and memories depend on sites and levels of damages. We had previously thought that adult motor neurons cannot regenerate and therefore rehabilitation causes recoveries of motor functions by compensations by residual neurons. Recently, central neurogeneses are reported (1), (2), the neurogenesis in damaged neurons as well as the residual neuronal compensation are targets for the recovery. Interestingly, it is reported that training brain infarcted rats and sham operated rats to reach food pellets (50 pellets in the first week and 100 pellets from the next week) by forelimbs for 40 days increased neurogenesis in dentate gyri compared to non-trained rats (3). We do not know whether the neurogenesis in the dentate gyrus is relevant to the recovery of forelimb motor functions or not but animal models are necessary for studies on drugs and therapy to promote rehabilitation and neurogenesis.

Although motor dysfunctions in rodents are made by various treatments such as cerebral infarction, spinal cord injury and brain trauma, levels of damages and recoveries are evaluated by a behavioral observation in rodents.

10-1 Gait Analysis

We can easily imagine a daily life and a rehabilitation using a wheelchair and a stick due to inconvenient legs. Functional disorders in hands and legs are common sequelae of the cerebral infarction and dysfunction of fore- and hindlimbs in rats and mice can be observed in gait behaviors.

There are two methods in the gait analysis that analyses of a stride length and etc. by footprints and of a leg motion by horizontal observation. The formers are recording and analyzing footprints by walking in a white paper with plantar black inks in rodents or by video imaging from the bottom. The video imaging method can analyze dynamic parameters such as a walking speed as well as static ones such as a stride length and a touching area. LED light is emitted inside the glass plate and is completely internally reflected, except at those areas where the animal touches the glass plate. In CatWalk by Noldus, illuminated footprints of rodents on the glass plate by this principle are video recorded from the bottom and analyzed. The gait analyses by CatWalk are reported in a mouse ischemia model by occlusion of a middle cerebral artery (4) and a photothrombotic stroke model by photosensitive dye and light irradiation in a rat (5). DigiGait by Mouse Specifics records and analyze a rodent on a transparent treadmill by high speed video image from the bottom.

In the horizontal video image, leg motions in a rodent walking on a treadmill are recorded by multiple cameras. Images of markers attached to the leg are obtained and discriminated by PC software and analyzed motions such as a joint. It is applied from motion-capture software for human to animals but a mouse is too small to be applied and realized in rats (6). Kinema Tracer by Kissei Comtec is available in Japan.

10-2 Staircase Test

Lafayette Staircase for Rats
A photo cited from Lafayette Instrument

Although forelimb dysfunctions affect gait in rats and mice because they walk with 4 limbs, we can measure only forelimb functions. We measure function in rodents to reach and get a small round pellets which is placed only one in an each step in a staircase. The animal gets more pellets by forelimb reaching length and functions of right and left limbs are separately measured. In this test rats and mice are deprived food to motivate to get food pellets. The animals are trained in the staircase and then the only established animals are treated to make motor dysfunction by such as cerebral infarction. We measure levels of dysfunctions and recoveries after the treatment (7).

It is an important point in this test that pellets in right and left sides cannot be gotten by an opposite forelimb and a mouth. Therefore, the staircase for rats and mice are different in a size and measurable sizes of animals are limited.

10-3 Rotarod

We observe whether mice or rats can stay on a slowly-rotating rod (a cylinder hollow or solid) or not and evaluate dysfunction of coordination in a rotarod test. Muscle relaxants such as benzodiazepines disrupt coordinative locomotion on the rotarod. If we increase a speed to rotate the rod, normal animals also fall. Therefore, we must study in the rotarod test with the speed which the normal animals can stay a while. In this condition, the rotarod disruption is reportedly not observed in the stroke models (5), (8).

10-4 Beam Walking Test

Lafayette Beam for Rats
A photo cited from Lafayette Instrument

We observe rodents walking on a beam and counts to step off the beam and slip paws. The beams for rats and mice are about 15 and 7 mm as a width, respectively and a tapering type is also available as shown in a figure. The beam is set high enough animals not to step down on a floor spontaneously and to walk on the beam. Their home cages set on a front edge motivate the rodents to walk. Increases in slips are observed in brain-impaired models of rats (8) and mice (9).

A ladder is also used instead of the beam (7).

10-5 Spontaneous Locomotion

A motor dysfunction in rodents might decrease locomotion, rearing behaviors and a traveling speed. It is reported that impairments and recoveries in a spinal cord injury model can be evaluated as the traveling speed (10). Please see "8. Locomotion and Food Intake 8-1-3-2 SCANET" for a measuring device.

10-6 Closing

Because motor functions can decline by peripheral impairments such as muscle relaxation or pains as well as dysfunctions of motor neurons, behavioral changes in rodents may reflect various factors. Although motor dysfunctions may decrease spontaneous locomotion in described above, anxiety state may affect the locomotion in an open field (see "1. Anxiolytics 1-2-4 Marble Burying Test"). We can expect to evaluate disruptions in the gait and the beam walking test by the muscle relaxation of 4 paws. However, benzodiazepines suppress spontaneous locomotion at a high dose causing the muscle relaxation and analyses of motor dysfunction by the spontaneous locomotion become difficult. Therefore, forced locomotion such as the rotarod test becomes an effective method in this case. You should select the methods according to types of motor dysfunctions and carefully consider various factors possibly affecting behaviors in rodents and evaluate dysfunctions and recoveries.