Deer Vineet, the first reason is that ethanol 70% is more effective in disinfecting than ethanol 100%. Pure ethanol can inactivate bacteria without actually killing them, since it is not able to fully permeate the bacterial cell wall. The second reason is that ethanol's odor may have an influence on rodent behavior. Hence it is better to use a lower concentration and to wait complete ethanol evaporation before placing the animal in the maze.

Hi MSc Sharma, most studies use ethanol 70% because this is enough to eliminate any olfactory cues present in the apparatus used. If any cues remain, the next animal tested may repeat the behavior of the predecessor or at least have its behavior altered. But if you use ethanol 70%, you have to dry out the ethanol (paper towel) before placing the next animal because, otherwise, the smell of the alcohol could be very strong and also alter behavior. Some studies use more diluted concentrations of ethanol, like 10 or 20%, to avoid that the apparatus smells a lot like alcohol. Some studies even don't use the ethanol because they want to leave the olfactory cues between animals. I think it depends on what you're trying to answer.

Just found this interesting article Article Effects of Various Cleaning Agents on the Performance of Mic...