Effects of neuropeptide Y injected into A1 noradrenergic nucleus on blood pressure and catecholamines in plasma of cats

The microinjection of neuropeptide Y (NPY) 0.75 and 1.5 micrograms into A1 noradrenergic nucleus of cats produced dose-dependent falls in mean arterial blood pressure of 2.0 +/- 0.6 and 4.9 +/- 2.4 kPa, respectively. NPY microinjection (1.5 micrograms) also produced marked decreases in noradrenaline (5 +/- 4 pmol.ml-1) and adrenaline (23 +/- 8 pmol.ml-1), but no significant change in dopamine in blood plasma. The results suggest that the depressor effect of NPY in A1 noradrenergic nucleus may be realized by not only reducing the release of noradrenaline in sympathetic terminals around the peripheral vascular beds but also inhibiting the sympathetico-adrenal system.