Overall distribution of glucagon-like immunoreactivity in the chicken retina: an immunohistochemical study with flat-mounts.
Pancreatic glucagon-like immunoreactivity (GLI) in the chicken retina was investigated by immunohistochemical methods with frozen sections and flat-mounts. Observations of the frozen sections showed that GLI is localized in the amacrine cells. Flat-mounts showed the GLI cells are evenly localized in the retina (n= or approximately 400/mm2) and composed to two types of cells--one is larger and the other is small. The former cell type occupies mainly the peripheral retinal region and the latter the central region. In addition, flat-mounts showed two types of GLI fiber plexuses in the inner plexiform layer; one is located in the area between laminae 2 and 3 and runs circularly and the other is located in lamina 1 and runs randomly. The relationship between GLI and cyclic AMP was also examined. an increase of the formation of cyclic AMP was caused by pancreatic glucagon in the chicken retina, suggesting that this peptide might have neurotransmitter or neuromodulator roles in the chicken retina.