BETA-ADRENOCEPTOR STIMULATION INCREASES NEUROPEPTIDE-Y RELEASE FROM SYMPATHETIC-NERVES IN INTACT RATS

This study was undertaken to assess in conscious normotensive rats the effects of beta-adrenoceptor stimulation on plasma neuropeptide Y (NP Y) levels. Wistar rats were subjected to adrenal demedullation on the right side and were either adrenalectomized or sham-operated on the le ft side. Eleven days later, the conscious rats were infused i.v. for 3 0 min with either isoproterenol (10 ng/min) or its vehicle. Plasma NPY levels were significantly lower (23.8 +/- 2.6 pM, means +/- S.E.M., n = 12, P < 0.01) in vehicle-treated medullectomized rats than in corre sponding sham-operated controls (36.7 +/- 4.1 pM, n = 12). The medulle ctomized rats infused with isoproterenol showed plasma NPY levels (36. 7 +/- 3.3 pM, n = 11) comparable to those of sham-operated rats having received the vehicle. These data therefore demonstrate that plasma NP Y levels are lower in rats without adrenal medulla and that in these a nimals isoproterenol increases NPY release, most likely by activating pre-synaptic beta-adrenoceptors.