Maze learning by adult rats after inhibition of neuronal multiplication in utero.

Rats whose mothers received hydroxyurea (HU, 1 or 2 g/kg) at 14 days of gestation had a 30% deficit in both brain and body weight at birth, when compared with controls. Number of brain cells at birth (mainly neurons) was reduced by 33-34%. A severe reduction in postnatal whole brain growth (31-33% in adulthood) was observed, but the cerebellum was relatively spared. In the Hebb-Williams maze text in adulthood HU animals made 28% more errors than controls over 12 problems. The differences were much more marked on certain problems and for HU animals with particularly small brains. In a T-maze spatial discrimination test in adulthood HU rats learned the initial response normally but, when required to reverse this response, showed a significant tendency to make more perseverative errors than controls.