Comparison of motor activity and anxiety-related behaviour between two lines of Sprague Dawley rats originating from the same stock

It is known that the anxiety-related behaviour may differ among rat substrains or lines, which might cause different results using the same animal test. More than 15 years ago the Institute of Cytology and Genetics, Novosibirsk (NOV) started breeding Sprague-Dawley (SD) rats obtained from Charles River (CR) Sulzfeld, Germany. Development of a line with potentially different behaviour could not be excluded. The behaviour of NOV-SD and CR-SD rats was analyzed using the open field, the hole board, the elevated plus maze (X-maze) and a free exploratory paradigm (FEP). NOV-SD rats and CR-SD rats were born and reared in an identical environment. Aged 50 days the rats were placed on the X-maze or the hole board and 14 days later in the open field. Aged 78 days the rats were tested in the FEP. NOV-SD rats were more active in all tests. They differed not in anxiety-related behaviour in the X-maze. In the FEP NOV-SD rats were less ‘anxious’. More NOV-SD rats explored the outside environment started exploring earlier, compared to CR-SD rats, indicating a difference in trait anxiety. In the hole board the CR-SD rats habituated better than the NOV-SD rats. Separation of the two lines for at least 45 generations did change behaviour related to trait anxiety and motor behaviour, but not state anxiety-related behaviour. This indicates arising of a line with partly different behaviour. In conclusion, using strains or substrains obtained from different breeders should be used with caution.