| Abstract: | The 5-hydroxytryptamine (5-HT) receptor in human umbilical artery was found to be similar to that in rabbit aorta. The pD2 was 7.45, pA2 for methysergide 8.63 and pA2 for phentolamine 6.21. Noradrenaline gave only very weak contractions at non-physiological concentrations. Amidephrine and xylazine did not contract human umbilical artery. It is concluded that there is no significant population of functional alpha-adrenoceptors in this vessel. The implications of these findings are discussed in relation to the control of the umbilical circulation. |
