NEUROPEPTIDE-Y RELEASE AND CONTRACTILE PROPERTIES - DIFFERENCES BETWEEN CANINE VEINS AND ARTERIES

During intense sympathetic activation, as occurs during hemorrhage, ve ins constrict to a greater degree than do arteries. This study determi ned if differences in the amounts or actions of the sympathetic cotran smitter neuropeptide Y released from perivascular nerves could contrib ute to these differences. Strips of canine mesenteric and popliteal ar teries and of saphenous and portal veins were superfused, and the rele ases of noradrenaline and neuropeptide Y evoked by transmural stimulat ion were assessed. Both compounds were released in greater amounts in the veins than in the arteries. In other experiments rings of each ves sel were mounted in organ chambers for isometric-tension recording. Ne uropeptide Y (up to 10(-4) M) did nor contract any vessel; however, at 3 x 10(-7) M it shifted the frequency-response and concentration-resp onse curves to noradrenaline in the arteries only. In the veins neurop eptide Y had no postsynaptic effect on strong contractions. These resu lts suggest that neuropeptide Y functions locally to affect vasoconstr iction of the arteries studied, and may have a different role in the v eins. Further, processes involving neuropeptide Y do not appear to acc ount for the differences in responsiveness of these arteries as compar ed to the veins during intense sympathetic stimulation.