In vivo analysis of adrenergic and serotoninergic constrictions of the rabbit saphenous vein

Abstract

We aimed to develop a model to study in vivo the rabbit saphenous vein pharmacology and to investigate constrictions mediated by adrenoceptor and 5-HT receptor subtypes. We used the technique of high precision ultrasonic echo-tracking for direct measurement of saphenous vein diameters in pentobarbital anesthetized rabbits. Saphenous vein constrictions induced in rabbits by the α 1-adrenoceptor agonist l-phenylephrine and the 5-HT 1B receptor agonist sumatriptan were comparable with those induced in dogs but those induced by the 5-HT 1B and 5-HT 7 receptor agonist 5-carboxamidotryptamine failed to appear in dogs. Dose-related constrictions of rabbit veins were obtained with l-phenylephrine and the α 2-adrenoceptor agonist dexmedetomidine. Frequency-related constrictions of rabbit veins induced by nerve stimulation were partially inhibited by an α 1-adrenoceptor or a postsynaptic α 2-adrenoceptor antagonist (prazosin and SKF 104,078) but not affected by the pre- and post-synaptic α 2-adrenoceptor antagonists BRL 44408 or rauwolscine. Constrictions of rabbit veins to sumatriptan and 5-CT were inhibited by GR 127935 and those induced by quipazine, a 5-HT 2 receptor agonist were prevented by ritanserin. The initial constrictions induced by 5-CT were followed by dilatations which were inhibited by the 5-HT 7 receptor antagonist mesulergine. These data indicate that rabbit saphenous veins, in vivo and at rest, respond to activation of 5-HT 1B and 5-HT 2 receptors, α 1- and α 2-adrenoceptors and nerve stimulation; the dilator effect mediated by 5-HT 7 receptor activation was also detected. The data validate a new animal model to study superficial vein reactivity and its pharmacological sensitivity.