Modulation of the stress response by coffee: an in vivo microdialysis study of hippocampal serotonin and dopamine levels in rat.

We studied whether coffee and its components (caffeine and chlorogenic acid) have stress-relaxing effects. In vivo brain microdialysis was used to characterize the effects of coffee, stress, and their interaction on the serotonergic and dopaminergic systems in the rat hippocampus. Restraint stress for 100 min caused a marked increase in dopamine and serotonin (5-HT) levels in the hippocampus, and then, 100 min resting (freely-moving) time reduced them to basal levels. Pretreatment with 33 mg/kg coffee or 1.7 mg/kg caffeine reduced the second restraint-induced increase in the neurotransmitters, especially 5-HT, but neither saline nor 1.7 mg/kg chlorogenic acid did. These results suggest that coffee contributes to the reduction of restraint-induced stress and that these effects could be due to caffeine. Possible mechanisms of the effects are considered. Copyright 2002 Elsevier Science Ireland Ltd.