Behavioral effects of exposure to caffeine during gestation, lactation or both.

Open-field behavior and latencies of emergence from a darkened chamber to a brightly lit arena were recorded at 1, 2, 4 and 6 months after birth in male and female rats that had been exposed to 26 or 45 mg/kg/day caffeine ingested by dams in their drinking water during gestation, 25 or 35 mg/kg/day during lactation or to the two low or high doses ingested during both gestation and lactation. One or both of the gestational or lactational doses reduced locomotor activity and increased defecation in the open field at all ages for males only. Rearing was decreased for both sexes by 25 mg/kg/day lactational caffeine. Numbers of rats that failed to or took longer than 1 min to emerge into the brightly lit arena were increased by 26 mg/kg/day gestational caffeine. All rats that had been exposed to either dose combination of caffeine during both gestation and lactation showed less locomotor and rearing activity, reduced tendencies to emerge within 1 min and, at 6 months of age only, more defecation in the open field. It was concluded that the effects of gestational and lactational exposure to caffeine were additive in their modification of the developing brain as reflected in decreased motor activity possibly arising from heightened emotional reactivity to the testing situation. Hypersensitivity of males to caffeine exposure during either gestation or lactation separately seemed to diminish when exposure was increased for all rats through experience of the drug during both gestation and lactation. Possible involvement of caffeine-induced increases in adenosine receptors in the type of results obtained was discussed.