Noradrenergic and neuropeptide Y-immunoreactive nerves in the pancreatic islets of spontaneously hypertensive rats.

Innervation by noradrenergic (NA) and neuropeptide Y-immunoreactive (NPY-IR) nerves to the pancreatic islets and the arteries supplying the islets was studied by immunocytochemistry in 6- and 20-week-old spontaneously hypertensive rats (SHR) and normotensive Wistar-Kyoto rats (WKY). Since both the NA and NPY-IR nerves follow the intra- and interlobular small arteries and innervate the islets, we examined mainly the innervation of intra- and interlobular small arteries by these nerves. The NA nerve density of the intralobular small arteries supplying the islets was significantly more extensive in 6-week-old SHR than in age-matched WKY (7.11 +/- 1.78 vs. 4.04 +/- 0.71 x 10(-2) micron/micron2, P < 0.001), and the NPY-IR nerve density of the intralobular small arteries was significantly more extensive in SHR than in WKY at 6 weeks of age (7.68 +/- 2.28 vs. 5.69 +/- 0.91 x 10(-2) micron/micron2, P < 0.05). The interlobular small arteries branching off the intralobular small arteries in SHR were also more innervated by NA (P < 0.05) and NPY-IR nerves (P < 0.001) than by those in WKY at 6 weeks of age. At 20 weeks of age, the NA and NPY-IR nerve densities of the intra- and interlobular small arteries were higher in SHR than in WKY, and showed an increase with age in both strains. In addition, the islet innervation by these nerves in cross-section appeared denser in SHR than in WKY.(ABSTRACT TRUNCATED AT 250 WORDS)