Distribution and regulation of substance P-related peptide in the frog visual system

Modulation of visual signal activity has consequences for both signal processing and for activity-dependent structuring mechanisms. Among the neuromodulatory agents found in visual areas are substance P (SP)-related peptides. This article reviews what is known about these substances in the amphibian retina and optic tectum with special emphasis on the leopard frog, Rana pipiens. It is found that the distribution of these SP-related peptides is remarkably similar to that seen in mammals. This suggests that study of model amphibian systems may significantly enhance our understanding of how neuropeptides contribute to visual system function and organization.