Differential expression of serotonin 5-HT2 receptors during rat embryogenesis

Serotonin (5-HT) is a neurotransmitter that also functions as a hormone and a growth factor. 5-HT is involved in numerous physiological actions and di splays complex pharmacological properties, As a growth factor, 5-HT plays a role in cell proliferation and differentiation of neuronal and nonneuronal tissue and it transduces its signals through more than fourteen subtypes o f 5-HT receptors. Since determination of the expression and distribution is important for understanding the role of the 5-HT receptors, we have develo ped an RNase protection assay (RPA) that allows the simultaneous analysis o f 5-HT2AR, 5-HT2BR, and 5-HT2CR per sample of RNA. This multiprobe set also comprises probes for two housekeeping genes, L32 and GAPDH, which control for sample-loading errors. Using this RPA probe set, we have examined the r elative expression of 5-HT2AR, 5-HT2BR, and 5-HT2CR in rat embryos inclusiv ely from embryonic day (ED) 9 to 21 of development. Our data indicate that 5-HT2AR levels gradually increased from ED11 to ED21. The expression of 5-H T2BR was decreased between ED9 to ED11 then remained relatively constant th rough ED21. 5-HT2CR was initially expressed at residual levels between ED9 and ED12 but dramatically increased to a peak level at ED13, then decreased by ED17. Expression of the 5-HT2 receptors in these tissues was confirmed independently by RT-PCR indicating that there is developmental regulation i n the expression of these receptors. The 5-HT2R multiprobe assay will be us eful for detecting relative changes in the expression of these receptors in developmental, normal and pathological tissues as well as for monitoring r elative changes in expression resulting from the use of pharmaceutical agen ts.