Serotonin uptake in the ectoplacental cone and placenta of the mouse.
The neurotransmitter serotonin (5-HT) was localized in the ectoplacental cone (EPC) and placenta of the day 9-12 (E9-12) mouse embryo in vivo and in whole embryo cultures, using immunocytochemistry with a specific 5-HT antiserum. In uncultured conceptuses, 5-HT immunoreactivity (5-HT IR) was most intense in the EPC at E9 (2-7 somites), particularly in giant cells around the periphery. Nuclear staining was observed in lightly staining giant cells and in small cells in the core of the cone. By E10 (18-24 somites) 5-HT IR in the placenta was less intense and almost exclusively limited to giant cells, where it was localized to chromatin-like material in nuclei. The same pattern and level of 5-HT IR persisted through E12. In the placenta, 5-HT IR appeared to be most intense in giant cells located near aggregations of platelets in decidual blood vessels. 5-HT IR was enhanced in cultured conceptuses, and further increased when exogenous 5-HT was added to the culture medium. Immunoreactivity was greatly reduced by adding the 5-HT uptake inhibitor fluoxetine to the culture medium, or culturing conceptuses in medium containing 5-HT depleted rat serum. Thus, 5-HT was apparently taken up from the culture medium. In conceptuses exposed to exogenous 5-HT, immunoreactivity in the placenta appeared as a gradient from the giant cells to the inner layers, suggesting that these cells may transport 5-HT toward the embryo. No evidence of 5-HT synthesis by the EPC/placenta was found. These results suggest that 5-HT present in the EPC/placenta is due to uptake, not synthesis. Possible sources and functions of 5-HT in the developing placenta are discussed.
Department of Cell Biology and Anatomy, University of North Carolina, Chapel Hill 27599-7090.
M S
MS
Yavarone
D L
DL
Shuey
T W
TW
Sadler
J M
JM
Lauder
D000818:Animals; D001692:Biological Transport / Q000187:drug effects / Q000502:physiology; D003470:Culture Media; D046508:Culture Techniques; D005260:Female; D007124:Immunoenzyme Techniques; D051379:Mice; D008813:Mice, Inbred ICR; D010920:Placenta / Q000187:drug effects / Q000378:metabolism*; D011247:Pregnancy; D012701:Serotonin / Q000096:biosynthesis / Q000378:metabolism*; D017367:Selective Serotonin Reuptake Inhibitors / Q000494:pharmacology; D014327:Trophoblasts / Q000187:drug effects / Q000378:metabolism*
D003470:Culture Media; D012701:Serotonin; D017367:Selective Serotonin Reuptake Inhibitors