Tachykinin peptides and receptors: putting amphibians into perspective.

The tachykinins form one of the largest peptide families in nature. In this review, we describe the comparative features of the tachykinin peptides and their receptors, focusing particularly on amphibians. We also summarize our systematic studies of the localization, characteristics, and actions of bufokinin, a toad substance P-related peptide, in its species of origin. In addition, we discuss the establishment of multiple isoforms of the NK1-like receptor in the toad, and their structure, pharmacology and tissue distributions. We conclude that tachykinin peptides and receptors are well conserved in terms of their structures, physiological functions and coupling mechanisms during tetrapod evolution.