Behavioral consequences of interference with CNS development in the early fetal period.

As a part of a series of investigations into the structural and functional consequences of interference with cell proliferation, mice were treated with 5-azacytidine during two stages of early fetal life. Treatment on either the twelfth or fourteenth day of gestation led to permanent significant reductions in body weight and brain weight. Behaviorally, the earlier treatment was associated with a delay in development of the righting reflex, permanent deficits in locomotor coordination, and hypoactivity. Treatment on the fourteenth day of gestation led to decreased passive avoidance, increased active avoidance, and hyperactivity--the same syndrome observed after treatment on the eighteenth day. Both treatments led to abnormal behavior on a spatial maze task. The developmental outcome of injuries induced in the early fetal period appears similar to the outcome of injuries at later stages of development.