NEUROPEPTIDE-Y IS EXPRESSED IN SUBPOPULATIONS OF INSULIN-PRODUCING AND NON-INSULIN-PRODUCING ISLET CELLS IN THE RAT AFTER DEXAMETHASONE TREATMENT - A COMBINED IMMUNOCYTOCHEMICAL AND IN-SITU HYBRIDIZATION STUDY

Neuropeptide Y (NPY) is known to occur in adrenergic and non-adrenergic nerves in rat pancreatic islets. Analysis of islet extracts has revealed local NPY synthesis after glucocorticoid treatment. The cellular localisation of NPY expression in rat islets following dexamethasone treatment (2 mg/kg daily, for 12 days), was investigated by a combination of immunocytochemistry (ICC) and in situ hybridisation (ISH). NPY-immunoreactive nerve fibres were seen in pancreatic islets of both control and dexamethasone-treated rats. In the controls weak NPY immunoreactivity but no NPY mRNA was observed in occasional islets. After dexamethasone treatment, clusters of islet cells distributed both centrally and peripherally displayed intense NPY immunoreactivity and NPY mRNA labelling. Immunocytochemical double staining and ISH combined with ICC for NPY and islet hormones revealed that most NPY expressing cells were identical with insulin cells; a few cells were identical with somatostatin or pancreatic polypeptide (PP) cells. In contrast, glucagon cells seemed to be devoid of NPY immunoreactivity and NPY mRNA labelling. Thus, in the rat, glucocorticoids cause a marked upregulation of NPY expression in islet cells, preferentially the insulin cells. The expression of NPY might represent an islet adaptation mechanism to the reduced peripheral insulin sensitivity.