Modulator role of neuropeptide Y in human vascular sympathetic neuroeffector junctions.

Reverse transcription polymerase chain reaction (RT-PCR) studies identified the mRNA coding for the Y1 and Y2 receptors in human mammary artery/vein and saphenous vein biopsies. Y1 receptors are expressed in vascular smooth muscles and potentiate the contractile action of sympathetic co-transmitters, adenosine triphosphate (ATP) and noradrenaline (NA); BIBP 3226, a competitive Y1 receptor antagonist, blocked the neuropeptide Y (NPY)-induced modulation. The Y2 receptor is expressed in sympathetic nerves terminals and modulates the pool of sympathetic co-transmitters released at the neuroeffector junction. NPY plays a dual role as a modulator of sympathetic co-transmission; it facilitates vascular smooth muscle reactivity and modulates the presynaptic release of ATP and NA. Sympathetic reflexes regulate human vascular resistance, where NPY plays a modulator role of paramount importance following increased sympathetic discharges, such as stress and vascular disease.