The effects of postnatal caffeine exposure on growth, activity and learning in rats

Caffeine is both ingested by pregnant women in their third trimesters and administered therapeutically to premature infants to stimulate respiration. This experiment attempted to delineate any persistent effects of low dose caffeine exposure during the first week of life in rats, since this time period provides an animal model equivalent to the human third trimester or premature infant exposure. Rat pups who had received either 1 or 9 mg/kg of caffeine during the first week of life grew more slowly, were hypoactive at two weeks of age, and were impaired on an operant spatial learning task as adults. Adding visual cues to the operant task did not improve their performance. The timing of the appearance of developmental landmarks, adult body weight and adult brain weight, however, were not affected by postnatal caffeine exposure. The persistent behavioral deficits noted after postnatal caffeine exposure were all opposite in direction to the acute effects of caffeine, and similar to the effects of adenosine. Thus the behavioral deficits reported here may reflect an upregulation of developing adenosine receptors that persists into adulthood subsequent to early chronic postnatal caffeine exposure.