EFFECTS OF NORADRENALINE AND VASOPRESSIN ANALOGS ON RESISTANCE AND CAPACITANCE VESSELS IN THE RAT HINDQUARTER PREPARATION

The isolated rat hindquarter preparation perfused at constant flow was used to determine resistance and capacitance responses from pressure and weight recordings. In response to noradrenaline at low concentrations, the capacitance effect was greater than the relative increase in total vascular resistance. 8-L-Arginine vasopressin showed capacitance responses only when the resistance vessel constriction was pronounced. Oxytocin and two synthetic analogues, 2-phenylalanine-8-ornithine vasopressin (Phe-Orn-VP) and 2-phenylalanine-8-ornithine oxytocin, showed varying potency for resistance vessel constriction but hardly any capacitance responses. However, when Phe-Orn-VP induced a small increase in total vascular resistance, a marked increase in post-capillary resistance was observed. The results are discussed in relation to a study in which the effects of vasopressin analogues were studied with intravital microscopy (Altura 1973).