Differential increase in neuropeptide Y-like levels and myenteric neuronal staining in diabetic rat intestine

Abstract

Neuropeptide Y is a regulatory peptide found in adrenergic and non-adrenergic neurons. Diabetes, which may cause autonomic neuropathy, induces an increase in hypothalamic neuropeptide Y (NPY) levels; thereby we measured the effects of chronic diabetes on neuropeptide Y in the intestine. Rats were injected with streptozotocin (65 mg/kg) and maintained for up to 20 weeks. Another group of rats was injected with 6-hydroxydopamine (50 mg/kg) × 2 to induce sympathectomy. Ileum and colon were harvested and both whole and microdissected intestine were (1) stained with antibodies to neuropeptide Y, vasoactive intestine polypeptide, and neurofilaments or (2) extracted for neuropeptide Y radioimmunoassay. Neuropeptide Y levels were similar under all conditions in the colon, but there was a trend toward an increase in the diabetic whole ileum. NPY levels were significantly increased in the dissected myenteric plexus ileal layer in diabetics. We noted an increase in the number of neuropeptide Y and vasoactive intestine polypeptide immunoreactive myenteric neurons in diabetics and after 6-hydroxydopamine-induced sympathectomy. Diabetes, and to a lesser extent sympathectomy, induced an increase in ileal neuropeptide Y levels and neuropeptide Y-staining myenteric but not submucosal neurons. Altered tissue levels of neuropeptide Y may account for certain of the gastrointestinal disturbances commonly seen in diabetes.