Eye and heart morphogenesis are dependent on the melatonin signaling in chick embryos

Abstract

Calmodulin is vital for chick embryos morphogenesis in the incubation time 48 h to 66 h when the rudimentary C-shaped heart attains an S-shaped pattern and the optic vesicles develops to the optic cups. Melatonin is in the extraembryonic yolk sac of the avian egg. Melatonin binds calmodulin. The aim of this study was to investigate the melatonin functions in the formation of the chick embryo optic cups and S-shaped heart, by pharmacology and immunoassays methods. Mel1a melatonin receptor immunofluorescence was distributed in the optic cups and rudimentary hearts. Embryonated chicken eggs at 48 h of incubation were separated into basal, control, and drug-treated groups. The treatment was applied or not in the egg air sac. Embryos were excised from the 66 h incubation eggs and analyzed. Embryos from the basal, control (distilled water), melatonin and 6-chloromelatonin (melatonin receptors agonist) groups had regular optic cups and an S-shaped heart, while embryos from the calmidazolium (calmodulin inhibitor) group did not. Embryos from the luzindole (melatonin receptors antagonist) and prazosin (Mel1c melatonin receptor antagonist) groups did not have regular optic cups. Embryos from the 4-P-PDOT (Mel1b melatonin receptor antagonist) group did not have an S-shaped heart. Melatonin, 6-chloromelatonin, and forskolin prevented the appearing of the abnormal chick embryos from the calmidazolium, luzindole, prazosin, and 4-P-PDOT groups. However, 6-chloromelatonin and forskolin (adenylate cyclase enhancer) prevented only partially the appearing of embryos with defective eye cups from the calmidazolium group. Results suggested that melatonin modulated the chick embryo morphogenesis via calmodulin and membrane receptors.