Abstract
It is still unclear whether catechin influences the brain function. We studied the effects of catechin on serotonin (5-HT) release from hippocampus, since 5-HT release in the brain dominates in uncomfortable conditions. 5-HT was measured in the hippocampus of unconscious Wistar rat, using in vivo microdialysis technique. We used five catechin derivatives; (+)catechin (CAT), (-)epigallocatechin gallate (EGCG), (-)epigallocatechin (EGC), (-)epicatechin gallate (ECG), (-)epicatechin (EC). Catechin concentration used was 10μM, except for CAT (1μM–1mM), and these compounds containing in the Ringer solution were perfused in the brain for 100 min. The 5-HT release by catechin was also studied in the conditions of high K or low K, and the addition of tetrodotoxin (TTX, 1μM), monoamineoxidase (MAO) inhibitors (pargyline, 0.1mM; clorgyline, 1mM) , and SSRI (fluvoxamine, 1mM). All catechin derivatives remarkably increased 5-HT release. EC was the most effective (270 times) in increasing 5-HT release, followed by CAT, EGC, ECG, EGCG in that order. CAT increased the 5-HT release in a concentration dependent manner, indicating that the ED50 is about 0.1mM. In addition, oral application of CAT (0.1mM) also led to increase of 5-HT release, suggesting that CAT penetrates the blood-brain barrier. 5-HT release by CAT was significantly reduced in the presence of MAO inhibitors and/or SSRI, while the release remained unchanged in the conditions of high K or low K, and the addition of TTX. These findings suggest that catechin functions in the brain as a MAO inhibitor and/or a SSRI. [J Physiol Sci. 2008;58 Suppl:S104]
