[A modified protocol for generating the simulated weightlessness rat model]

To introduce a modified protocol for generating the simulated weightlessness rat model by hindlimb unloading.

Ninety male adult SD rats were randomly divided into three groups: the control group, classical suspension group and modified suspension group (n=30/group). In the classical suspension group, a strip of medical adhesive tape was attached to the tail, with horizontal filament tape wrapping. A piece of gauze was wrapped around the tail at the outermost layer and the tail was suspended for hindlimb unloading. In the modified suspension group, a layer of plastic net was added between the horizontal filament tape and the gauze to reduce the squeeze on the tail as a buffer zone and ensure proper circulation of the tail. After 4 weeks of suspension, damage to the tail and sheath detachment were observed. Meanwhile the body weight and right soleus wet weight of rats were measured.

The ratio of right soleus wet weight to body weight was decreased significantly in both the classical suspension group and the modified suspension group compared with the control group, while there was no difference in body weight among the three different groups. Importantly, the incidence of tail ischemia and necrosis (13.3% vs 40.0% in the classical suspension group) and the incidence of sheath detachment from tail (3.3% vs 26.7% in the classical suspension group) were significantly lower whereas the success rates of model (33.3% vs 83.3% in classical suspension group) was significantly higher in the modified suspension group.

The modified protocol decreases the incidence of tail necrosis and sheath detachment in the rat tail suspension and increases the success rate of the hindlimb unloading rat model, with improved simplicity and practicability.