Strain Differences of Postnatal Development of Righting Reflex, Traction and Motor‐Coordination, and Emotional Behavior in Rats

Abstract Litters from the non‐treated dams in Sprague‐Dawley (SD) and Wistar rats which are used most frequently in reproduction studies were observed for strain differences concentrating on the behavioral development during the early postnatal stage. During the period before the eyelids open, the Wistar rats showed significantly earlier development of postural reflex and traction than the SD rats. However, during the period after eyelids open, the significant difference between these two strains disappeared. The numbers of fallings from a rotorod, ambulation, and rearing in the SD strain significantly increased as compared with those in the Wistar strain. These findings suggest that proper caution should be paid to the developmental period for observing the postural reflex and traction response for the particular strain.