The effects of maternal hyperphenylalaninemia on learning in mature rats

Pregnant rats were given a diet supplemented with 0.5% alpha-methyl-phenylalanine and 3% phenylalanine from the 12th day of gestation to term. Compared to unsupplemented controls, maternal serum phenylalanine was elevated 8-10-fold. Experimental litters did not differ from controls in number of offspring, birth weight, or subsequent growth on an unsupplemented diet. At 8 weeks of age, animals were tested for latent learning on a 4-arm maze, and at 10 weeks, they were tested for observational learning with littermates in a food preference paradigm. In both tests, experimental animals did learn, but significantly less than controls. The data suggest that maternal hyperphenylalaninemia, induced as a model for the inborn error, phenylketonuria, can lead to learning deficits later in the lives of offspring.