MATERNAL VASOACTIVE-INTESTINAL-PEPTIDE AND THE REGULATION OF EMBRYONIC GROWTH IN THE RODENT

Vasoactive intestinal peptide (VIP) has been shown to regulate early p ostimplantation growth in rodents through central nervous sq stem rece ptors, However, the source of VIP mediating these effects is unknown. Although VIP binding sites are present prenatally, VIP mRNA was not de tected in the rat central nervous system before birth and was detected in the periphery only during the last third of pregnancy, In the pres ent study, the embryonic day (E11) rat embryo/trophoblast was shown to have four times the VIP concentration of the E17 fetus and to have VI P receptors in the central nervous system. However, no VIP mRNA was de tected in the Ell rat embryo or embryonic membranes by in situ hybridi zation or reverse transcriptase-PCR, RIA of rat maternal serum reveale d a peak in VIP concentration at days E10-E12 of pregnancy, with VIP r ising to levels 6-10-fold higher than during the final third of pregna ncy, After intravenous administration of radiolabeled VIP to pregnant female mice, undegraded VIP was found in the E10 embryo, These results suggest that maternal tissues may provide neuroendocrine support for embryonic growth through a surge of VIP during early postimplantation development in the rodent.