Acute interaction between ethanol and serotonin metabolism in the rat

The effect of acute ethanol on peripheral serotonin (5HT) metabolism was studied in Sprague-Dawley rats. Four hours after a single dose of ethanol (1.0 g/kg) administered into the stomach, a significant increase in the 5HT level in stomach tissue and a decrease in ileum was observed. The level of 5-hydroxyindole-3-acetic acid (5HIAA) was increased in urine, while increased concentrations of 5-hydroxytryptophol (5HTOL) occurred in jejunum, ileum, spleen and urine. After 7-9 h when the blood ethanol concentration had returned to zero, 5HTOL levels were still higher than control values in jejunum, ileum and urine. At 4 h, an elevated ratio of 5HTOL to 5HIAA was observed in urine and ileum (by approximately 2-fold), liver (approximately 3-fold), and spleen (approximately 5-fold), whereas the ratio was reduced in stomach. In urine and spleen, this metabolic shift persisted after 7-9 h. The 5HTOL level in bile was increased by approximately 3.5-fold after 8 h. 5HIAA was not detectable in bile. The present results indicate that the rat has a much higher proportion of 5HTOL formation than man under normal conditions. The rat does not appear to be an ideal model for studying the interaction between ethanol and 5HT metabolism in man.