In Utero Caffeine Exposure Affects Feeding Pattern and Variable Ratio Performance in Infant Monkeys

Abstract

Adult female monkeys (Macacafascicularis) were exposed via their drinking water to 0.0, 0.15, or 0.35 mg/ml of caffeine prior to and throughout pregnancy. Caffeine exposure resulted in a dose-related increase in the number of infant deaths at parturition. Additional females were added to the control group and the original groups were rebred, which resulted in 16, 13, and 9 live infants in control, low-dose, and high-dose groups, respectively. During pregnancy the mean serum caffeine levels were 3.4 and 10.3 μg/ml and the mean serum theophylline levels were 6.6 and 12.9 μg/ml for the low-dose and high-dose groups, respectively. Infants were separated from their mothers at birth and reared in a primate nursery to facilitate evaluation of infant performance on a variety of behavioral tasks. Infant formula consumption was monitored by a computer-based system 19 hr per day until 30 days of age. At 30 days of age infants were trained to press a button for a formula reward, after which they performed on a variable ratio schedule for a 14-day period. Monitoring of feeding pattern revealed that the treated infants spent significantly more time feeding than controls. On the variable ratio schedule, the high-dose group had consistently longer pause times and longer inter-response times than the control group. The results from this study indicate that in utero exposure to caffeine and its metabolites results in altered behavioral patterns in infant monkeys.