Host Defense Peptides from Australian Amphibians: Caerulein and Other Neuropeptides

Abstract

Amphibians possess several potent neuropeptides such as caerulein in their dorsal skin secretions. Australian anurans produce some of the most potent neuropeptides yet identified in the amphibian integument, including the caeruleins and the uperoleins. Caerulein was first isolated from dried skins of the Australian Green Tree Frog. Caerulein is common in a number of frog genera and has multifaceted activity at nanomolar concentrations. It causes smooth muscle contraction, reduces blood pressure, has gastrin-like activity, and modifies satiety, sedation, and thermoregulation. A number of modified caeruleins occur in Australian frogs of the genus Litoria. Caerulein is a primary host-defense peptide, and it also regulates dermal physiological action in the frog. It exhibits a spectrum of activity similar to those of the mammalian intestinal hormones gastrin and cholechystokinin. Uperoleia species of toadlets produce a number of tachykinin- and bombesin-type neuropeptides, including uperolein, while froglets of the genus Crinia produce a variety of disulfide-containing neuropeptides that cause smooth muscle contraction at nanomolar concentrations. © 2006 Elsevier Inc. All rights reserved.