Effects of estrogen, G-protein coupled estrogen receptor agonists and inhibitors on 5-hydroxytryptamine levels in ovariectomized rats

Abstract

Objective To explore the effect of estrogen on 5-hydroxytryptamine (5-HT) levels in ovariectomized rats and the role of the G protein-coupled estrogen receptor (GPER) in it. Methods Fifty 12-week-old female mice were randomly divided into two groups in which 30 rats were ovariectomized to establish the model of menopause, the other 20 rats were sham-operated. Ovariectomized rats were subdivided into 6 groups, including injection with estradiol (E2), E2+GPER specific agonist (G1), G1, inhibitor (G15), E2+G15, oil for one week; sham operation rats were injected with G1, G15, blank and oil for 1 week. Blood samples were taken from the heart before operation, and before and after treatment. Serum 5-HT levels were measured by enzyme-linked immunosorbent assay (ELISA). Results After ovariectomy, the level of 5-HT was significantly decreased (P=0.031) in rats and the level of 5-HT did not change significantly after sham operation (P=0.380). Serum levels of 5-HT were significantly elevated in ovariectomized rats after one week of continuous injection of E2 (P=0.007). There was no significant change in 5-HT levels after G1 or G15 injection alone or E2+G1 or E2+G15 injection after one week. Conclusion Serum 5-HT levels were significantly decreased after ovarian castration, whereas estrogen treatment resulted in elevated 5-HT levels. No significant effect of G1 and G15 on serotonin levels in rats was found. However, the mechanisms by which estrogen regulates mood disorders and 5-HT, and the role that GPER plays in them still need to be further explored and studied. Key words: G protein-coupled estrogen receptor (GPER); Ovariectomized rats; Estradiol (E2); 5-hydroxytryptamine (5-HT)