The extended application of The Rat Brain in Stereotaxic Coordinates in rats of various body weight

Stereotaxic procedures in rats are frequently used in neurological research. The commonly used rat brain stereotaxic atlases areThe Rat Brain in Stereotaxic Coordinates, the second most cited book in science, and Stereotaxic Atlas of Rat Brain (in Chinese) which based on Wistar rats of 290 g and SD rats of 225 g, respectively. However, rats of different weight are frequently used, while the stereotaxic coordinates of their brain regions show obvious differences with the rats on which the atlases were based.The craniometric parameters were measured as accurately as possible, then curve fitting equations obtained from the parameters were used to deduce the relative coordinates in rats of different weight for the first time.The results revealed that if the coordinates of target brain region were defined as AP(a), ML(b), DV(c) in "standard" rats, the corresponding coordinates AP(a'),ML(b'),DV(c') for rats weighingm(g) were described as follows: For Wistar rats using The Rat Brain in Stereotaxic Coordinates: a' =0.138×lnm+0.1770.138×ln290+0.177×a b' =0.055×lnm+0.5150.055×ln290+0.515×b c' =0.054×lnm+0.7060.054×ln290+0.706×c-0.00012×m-290 and for SD rats using Stereotaxic Atlas of Rat Brain(in Chinese): a' =0.127×lnm+0.1760.127×ln225+0.176×a b'=0.049×ln⁡m+0.5560.049×ln⁡225+0.556×b c' =0.077×lnm+0.6040.077×ln225+0.604×c-0.00010×m-225 Unit of a, b, c, a', b', c' are centimeter, unit of m is gram. Comparison with existing method: The Rat Brain in Stereotaxic Coordinates is applicable for rats weighing about 290 g, while our equations extended the use of atlas to rats weighing 90-400 g.In this manner, the application of the rat brain atlases could be extended and the results would be of great help in stereotaxic procedures.