Gastric neuropeptides and gastric motor abnormality in streptozotocin-induced diabetic rats: observation for four weeks after streptozotocin.

Alterations of gastric calcitonin gene-related peptide and substance P content and gastric emptying in early stages of streptozotocin-induced diabetic rats were investigated. Diabetes was induced by intravenous injection of streptozotocin (50 mg/kg) in male Wistar rats. Gastric emptying of phenol red solution and calcitonin gene-related peptide and substance P content of gastric walls, measured by radioimmunoassay, was assessed two and four weeks after streptozotocin injection. Gastric emptying two weeks after streptozotocin was delayed (32+/-9%) and that four weeks after was enhanced (73+/-2%) compared with nondiabetic control rats (50+/-3%). Calcitonin gene-related peptide content of the gastric antrum and corpus was increased two weeks after and decreased four weeks after streptozotocin, while gastric substance P content was not changed at any time in diabetic rats. Insulin treatment reversed alterations of gastric emptying and calcitonin gene-related peptide content. The delayed gastric emptying in two-week diabetic rats was reversed by CGRP antagonist and the enhanced gastric emptying in four-week diabetic rats was reversed by CGRP pretreatment. These results suggest a possible relationship between gastric calcitonin gene-related peptide and abnormal gastric motility in diabetic state.