THE INFLUENCE OF BETAMETHASONE AND DEXAMETHASONE ON MOTOR DEVELOPMENTIN YOUNG-RATS

Synthetic corticosteroids such as dexamethasone and betamethasone are widely used in clinical practice of the perinatal period to enhance lu ng maturation. However, indications emerged both on the basis of inves tigations in humans and in experimental animals that such treatment le ads to abnormal brain development. In the present study, the neurologi c development and the development of locomotion were studied in two gr oups of rats injected either with dexamethasone or with betamethasone on their 3rd and 4th d, and this was compared with development in a gr oup Of control rats injected with saline. Each group consisted of 12 r ats. Neurologic reflexes were tested daily and the rat's physical deve lopment (body weight and age at eye opening) was noted from the 4th un til the 21st d. Locomotion was recorded on videotape and analyzed duri ng playback runs. Resuits indicated a growth retardation in both group s of rats treated with corticosteroids, but remarkably, the opening of the eyes was advanced by about 1 d in the dexamethasone group compare d with control rats and rats treated with betamethasone. Several refle xes showed normal development, but the negative geotaxis and free-fall righting responses developed retarded. Locomotion in both experimenta l groups was characterized by a postural tremor and an abnormal postur e during walking from the 9th until the 15th d. Although the walking p attern after this age became fluent, the gait width remained abnormall y increased until the 20th d. Our results indicate that both dexametha sone and betamethasone interfere with the development of vestibular an d cerebellar functions involved in complex motor patterns.