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Neuropeptide Y (NPY) exerts its cardiovascular effects via NPY receptor antagonists. In a study of vasoconstriction in anesthetized pigs, the application of nonpeptide, selective Y1 receptor antagonists BIBP3226 and BIBP3435 on vascular smooth muscle in vivo antagonized Y1 receptors, inhibited sympathetic neurotransmitter release and resulted in muscle smooth muscle contraction evoked by sympathetic nerve stimulation. These results indicate that exogenous agonists mediate vasoconstrictor response to nerve stimulation.

Hypoxia has marked effects on artery calibre, which reflects important physiological control mechanisms that are altered in disease states. Hypoxia modifies the release of mediators, especially from the endothelium, and influences smooth muscle membrane potential and Ca2+ regulation. In this review, Roger Wadsworth evaluates the vasoconstrictor and vasodilator effects of hypoxia studied in vitro. In the future, drugs developed to act on the mediators or smooth muscle may be beneficial in the therapy of, for example, pulmonary hypertension or coronary vasospasm.

Blocking of endothelin receptors, which consist of subtypes ET (sub A) and ET (sub B), is being studied by scientists to promote the dilation of blood vessels. To mediate vasoconstriction, it is improtant to determine the receptor subtypes that can be acted upon by the receptor antagonist agents. Encoding of mRNA revealed that not only ETA receptors are present in humans, but also ETB. Comparison of the agonist and antagonist patterns of the two subtypes confirmed that both ETA and ETB are expressed in human blood vessels.