Melatonin receptor mRNA localization and rhythmicity in the retina of the domestic chick, Gallus domesticus.

The indoleamine hormone melatonin is synthesized and released by photoreceptors during the night within the chick retina, and confers timing information to modulate retinal physiology. Three subtypes of melatonin receptor with nearly identical pharmacological profiles have been described in chickens and are present in the retina. In this study, the spatial localization and temporal pattern of the mRNA for each of these receptors within the retina are described.

Functional melatonin receptors and metabolic coupling in cultured chick astrocytes.

Melatonin is an important hormone regulating circadian clocks in birds, but the specific cellular sites of action are not completely known. The present study was designed to determine whether astrocytes derived from chick brain contained functional melatonin receptors. Primary cell cultures of diencephalon astrocytes that express glial fibrillary acidic protein (GFAP), but not neuron-specific enolase (NSE) immunoreactivity, were employed to determine the cellular distribution and physiological role for the three known receptor subtypes.