Effects of postnatal caffeine exposure through dam's milk upon weanling rats

The effects of postnatal caffeine exposure received through mother's milk were examined in rat pups by administering 0.0125 or 0.05% caffeine solution to the dams throughout lactation. Offspring of caffeine-treated dams showed significantly earlier onset of auditory startle and air righting reflexes. No direct effects of treatment were observed on eight measures of open field activity. At weaning, high-dose caffeine pups exhibited a transient increase in caffeine acceptance in two-bottle taste preference tests and showed cyclic exaggerations in caffeine preference-aversion functions which persisted throughout the 22-day postweaning test period. The caffeine levels in the dams' milk had a 30-fold daily fluctuation reflecting the fluid ingestion pattern related to the light-dark cycle and caffeine elimination rate. Caffeine concentrations in the brains of the pups varied between 0.01 and 9.0 micrograms/g.