Pancreatic hormone response to neuropeptide Y (NPY) perifusion in vitro

Available data on the effect of neuropeptide Y (NPY) on insulin release are conflicting and little data exist regarding the effect of NPY on glucagon secretion. The purpose of the present study, therefore, was to characterize the direct effect of NPY on the release of these pancreatic hormones and to examine the role of glucose on these interactions. Using a perifused mouse islet system, we found that NPY suppressed both basal and glucose-stimulated insulin secretion. Thus, basal insulin release assessed as mean integrated area under the curve/20 min (AUC/20 min) decreased from 1446 +/- 143 pg to 651 +/- 112 pg (P less than 0.05) with the addition of 2 x 10(-8) M NPY and the AUC/20 min for glucose stimulated insulin output decreased from 1973 +/- 248 pg to 1426 +/- 199 pg (P less than 0.05). In both cases, this inhibitory effect was followed after removing NPY by a stimulation of insulin secretion which was typical of a 'rebound off-response'. In contrast, NPY exerted a stimulatory effect on basal glucagon release and significantly reversed the suppressive effect of high glucose on glucagon output. The basal glucagon AUC/20 min increased from 212 +/- 103 pg to 579 +/- 316 pg (P less than 0.05), while glucagon secretion in the presence of 27.7 mM glucose increased from 75 +/- 26 pg to 255 +/- 28 pg (P less than 0.01). In conclusion, we have shown that the direct effect of NPY on the endocrine pancreas is to suppress insulin but stimulate glucagon secretion. These data are compatible with a role for NPY in the regulation of pancreatic hormone output.