Amines and choline acetyltransferase in rat intestine

Long-lasting microbial dysbiosis and altered enteric neurotransmitters in adult rats following adolescent binge ethanol exposure

Human alcoholism and ethanol exposure of adult mice cause acute microbial dysbiosis. Adolescent binge drinking is common, but the effect of adolescent ethanol exposure on the adult microbiome and enteric neurotransmitters has not been studied. In the current study, male Wistar rats received adolescent intermittent ethanol (AIE) treatment, and fecal samples were collected on postnatal day (P)54 and P95 for bacterial 16S rRNA amplicon sequencing. Cecal tissue was collected on P95 for analysis of innate immune and neurotransmitter marker expression. At the genus level, AIE treatment altered the relative abundance of several microbes, including decreased relative abundance of Dehalobacterium and CF231 (a member of the Paraprevotellaceae family) that persisted into adulthood. Across aging, the relative abundance of several microbes was altered in both control- and AIE-treated rats. At P95, AIE exposure was associated with increased cecal serotonin levels and reduced choline acetyltransferase gene expression. Taxonomic shifts at P54 and at P95 suggest that AIE causes both immediate and lasting microbial dysbiosis. The lasting microbial dysbiosis was accompanied by alterations of enteric neurotransmitters.

5-HT metabolism in the intestinal wall of the rat-I. The mucosa

Serotonin (5-HT) metabolism was studied on isolated mucosa of the rat caecum in order to determine its characteristics in enterochromaffin cells. High levels of 5-HT were found in these cells and weak catabolic processes were demonstrated. Enterochromaffin cells of the mucosa are able to synthesize ((3)H)5-HT from ((3)H)tryptophan in vitro indicating that these cells might contain tryptophan hydroxylase. In addition, a high affinity uptake of exogenous ((3)H)5-HT is demonstrated. These results show that enterochromaffin cells of the mucosa present similar biochemical properties compared to those described for serotoninergic neurons of the central nervous system.

Plasma levels of 5-HT and 5-HIAA increased after intestinal ischemia/reperfusion in rats

Intestinal ischemia/reperfusion (I/R) causes serious systemic injury, mainly from a variety of bioactive substances released from the injured intestine. To assess the possible roles of serotonin (5-hydroxytryptamine, 5-HT), a bioactive amine mainly stored in the intestine, in I/R injury, we assayed the levels of tryptophan, 5-HT, and 5-hydroxyindole acetic acid (5-HIAA) in the blood and intestine in a rat I/R model. Plasma 5-HT increased significantly over time after reperfusion; the plateau level was obtained 4 h after reperfusion and was associated with an increase in 5-HIAA. Plasma tryptophan levels declined gradually after reperfusion. The ratio of 5-HIAA/5-HT was significantly higher in I/R rats than in control rats, suggesting that elevated 5-HT was quickly metabolized in the systemic circulation. In the intestine, 5-HT decreased dramatically, whereas tryptophan increased. This phenomenon was prominent in the severely damaged intestine. These findings suggest that the injured intestine released large amounts of 5-HT, whereas its synthesis in the injured intestine was suppressed. An increase in 5-HT in the circulation may be related to various circulatory disturbances observed in humans after intestinal ischemia.

Effect of streptozotocin-induced diabetes mellitus on serotonin measures of peripheral tissues in rats

The present study was conducted to examine whether experimental diabetes (streptozotocin-induced) promotes changes in serotonin (5HT) measures of peripheral tissue. Platelet-free plasma 5HT, tryptophan and 5-hydroxyindolacetic acid (5HIAA), whole blood 5HT and renal, liver, intestinal and lung 5HT and 5HIAA levels were measured in rats of four experimental groups: control, diabetic, diabetic+insulin and non-diabetic+insulin. Several serotonin measures were unaltered in all four experimental groups, i.e. plasma, liver and lung 5HT and 5HIAA levels. Whole blood 5HT levels descended about 50% in diabetic rats, then recovered their proper levels after 1 week of insulin therapy. Diabetic animals had a significantly greater intestinal 5HT concentration (+50% versus control), while intestinal 5HIAA levels did not achieve statistical significance despite a -26% decrement in their value. Both renal 5HT and 5HIAA levels were decreased in diabetic animals and recovered with insulin therapy. Peripheral tissue 5HT measures were not varied by insulin administration to non-diabetic animals. The results are consistent with a 5HT release, which is diminished in enterochromaffin cells and enhanced in platelet concomitantly to a minor platelet 5HT uptake, for explaining alterations of plasma/blood 5HT measures in experimental diabetes, and with a diminished synthesis of 5HT for explaining renal changes.