Tyrosine administration to pregnant rats induces persistent behavioral modifications in the male offspring

Pregnant rats were given, by stomach intubation, 1-tyrosine (20 or 500 mg/kg), beginning on day 11 post-coitus. Tyrosine or saline solution administrations were continued on a once-daily basis until day 20 of gestation. When male offspring were seventy days old, the spontaneous locomotor activity, open field test, swim test and motor ability test were performed. The offspring treated with large tyrosine doses showed a marked increase in both spontaneous locomotor activity and open field locomotion as adults. However, activity in the swim test decreased. The number of defecation boluses produced in the open field test and the motor ability in the rotating rod test diminished. The behavior of the rats treated with small doses of tyrosine was similar, in all tests performed, to that of rats treated with saline solution. These findings strongly suggest that a large increase in diet tyrosine during pregnancy modifies the behavior of male offspring.