Bufokinin: immunoreactivity, receptor localization and actions in toad intestine and mesenteric circulation

In this study, we have mapped the immunoreactivity and the binding sites fo r bufokinin, a tachykinin peptide from the toad intestine. Dense bufokinin- immunoreactive fibers were present at the myenteric plexus, but no cell bod ies were stained, suggesting an extrinsic origin. Bufokinin nerve fibers we re also associated with submucosal blood vessels and mesenteric arteries. A utoradiographic binding sites for [I-125]Bolton-Hunter-bufokinin were dense ly localized over the intestinal circular and longitudinal muscle, submucos al blood vessels and the endothelium of mesenteric arteries. Mesenteric vei ns had minimal immunoreactivity and binding sites. In the anesthetized toad , topical application of bufokinin onto the mesentery caused a 2.7-fold inc rease in arterial blood how, observed using intravital microscopy. This stu dy supports a role for bufokinin as an endogenous spasmogen and hemodynamic regulator in the toad intestine. (C) 2000 Elsevier Science Inc. All rights reserved.