“Objective. to investigate the effects of 5-hydroxytryptamine (5-ht) and intestinal flora on depression-like behavior induced by lead exposure in rats. methods. 30 healthy spf adult male sd rats were randomly divided into control group and lead exposure group. the depression-like behavior of rats was detected. the blood, striatum, and intestinal tissue were collected. the lead content was detected by icp-ms. the mrna expressions of chga, tph1, 5-ht, and 5-ht3r were tested by qrt-pcr. the content of 5ht was checked by hplc-ecd. the content of 5-ht3r was detected by elisa. the protein expressions of 5-ht, 5-ht3r, chga, and tph were gauged by immunohistochemistry. fecal samples were collected, and the composition of intestinal flora in experimental rats was analyzed by 16 s rna metagene sequencing. results. lead exposure can greatly cause depression. the content of 5-ht in blood and striatum in the lead exposure group decreased, and the expression levels of 5-ht, 5-ht3 r, chga, and tph in the intestine decreased distinctly. compared with the control group, the distribution of a-polymorphism related indexes simpson, chao1, shannon, and ace in rats with depressive-like behavior after lead exposure was significantly increased; in the lead exposure group, there were 61 different operational taxonomic units (outs) in intestinal flora at the family level. based on linear discriminant analysis, it was found that the key bacteria were lactobacillaceae and bifidobacteriaceae, and their abundance decreased evidently in the lead exposure group. conclusion. lead exposure improves depressive-like behavior by affecting intestinal flora and regulating neurotransmitter 5-ht through the intestinal-brain axis.”

“Oxytocin (oxt) and serotonin (5-ht) are essential neurotransmitters associated with the behavior of animals. recently, we found that the plasma concentration of oxt is positively correlated with horse docility and friendliness toward humans. however, the relationships between the neurotransmitters and other temperaments such as fearfulness, dominance, and trainability are unknown. this study aimed to identify whether the plasma concentration of oxt or 5-ht is correlated with fearfulness, dominance, and trainability of horses. blood samples of 34 horses were collected at the horse industry complex center of jeonju kijeon college. the concentration of oxt and 5-ht was measured in the plasma samples using enzyme-linked immunosorbent assays. the fearfulness, dominance, and trainability of horses were scored by three professors who were very familiar with the horses. one-way analysis of variance with the least significant difference post-hoc analysis was used to compare the scores for fearfulness and dominance among groups. the trainability of horses was compared using the student t-test. the 5-ht was negatively correlated with dominance, but it had no relation with fearfulness. the oxt appeared to be negatively correlated with fearfulness and dominance in horses. furthermore, oxt was positively correlated with the trainability of horses. additionally, 5-ht appeared to enhance trainability. in conclusion, the concentration of oxt or 5-ht in horse blood plasma can be used as a biomarker to monitor the fearfulness, dominance, or trainability of horses.”