Glucagon receptor agonists and antagonists affect the growth of the chick eye: A role for glucagonergic regulation of emmetropization?

Abstract

PURPOSE. In chicks, plus defocus retards eye growth, thickens the choroid, and activates glucagonergic amacrine cells, probably releasing glucagon. Glucagon receptor antagonists (expected to inhibit compensation to plus defocus) and agonists (expected to block myopia induction by form deprivation) were administered to eyes of chicks, to test the hypothesis that glucagon mediates the induction of changes in eye growth by plus defocus. METHODS. Seven-day-old (P7) chick eyes were injected intravitreally with peptides at concentrations of ∼10-9 to 10-5 in 20 μL (injection volume). The glucagon-receptor antagonists [des-His1,des- Phe6,Glu 9]-glucagon-NH2 (des-Phe6-antagonist) and [des-His1,Glu9]-..