Intravenous administration of 5-HTP elevated 5-HT concentration in brain and blood in rat with gastrointestinal resection.

Abstract

The purpose of this study is to evaluate whether the level of serotonergic activity in brain can be estimated by measurement of serotonin (5-HT) concentration in blood. Although it has been long suggested that the monoamines including 5-HT does not transport across the blood-brain barrier (BBB), a recent study demonstrated an existence of 5-HT transport system at BBB by in vitro study. The present study was conducted to evaluate this notion by in vivo study. We examined a change in 5-HT level in whole blood, when brain 5-HT level was elevated by intravenous administration of 5-HTP in an anesthetized, spontaneously breathing rat with and without gastrointestinal resection, namely non-GI rat and control rat. Brain 5-HT level was measured by microdialysis method and HPLC system: samples were corrected every 10 minutes in medial prefrontal cortex in non-GI rat and control rat. We also measured 5-HT concentration in whole blood before and after 5-HTP loads. We found that blood 5-HT level showed a clear augmentation whenever brain 5-HT level was elevated by 5-HTP either non-GI rat or control rat. These results indicated that an increase in blood 5-HT level was induced an increase in brain 5-HT level. [Jpn J Physiol 54 Suppl:S216 (2004)]