Melatonin binding sites in brain of the 2-day-old chicken: an autoradiographic localisation.
Melatonin, released in a circadian manner from the avian pineal gland into the circulation, is concentrated in distinct brain areas, possibly by receptor-mediated uptake mechanisms. For anatomical localisation of putative melatonin receptors in birds, cryostat-cut, coronal 15 microns brain sections of 2-day-old chicken were investigated by means of in vitro receptorautoradiography, using 125I-melatonin as a ligand. Binding occurred in brain structures receiving or mediating visual or auditory sensory input. Binding characteristics were investigated in homogenates of a brain region labelled by 125I-melatonin and showed to be specific and saturable (Kd: 87.2 pM; Bmax: 16.1 fmol/mg protein). Results confirm that a wealth of structures in chicken brain are equipped with putative melatonin receptors, including the visual suprachiasmatic nucleus. However, as results show that fewer structures were labelled in the brain of 2-day-old chicken as compared to a similar investigation conducted with 12-day-old chicken, developmental changes in distribution and/or density of putative melatonin receptors might be present.
Stehle
J
J
Department of Anatomy, University of Mainz, Federal Republic of Germany.
D000818:Animals; D000831:Animals, Newborn; D001345:Autoradiography; D001921:Brain / Q000378:metabolism*; D002645:Chickens / Q000378:metabolism*; D008297:Male; D008550:Melatonin / Q000378:metabolism*; D044094:Receptors, Melatonin; D017981:Receptors, Neurotransmitter / Q000378:metabolism*
D044094:Receptors, Melatonin; D017981:Receptors, Neurotransmitter; D008550:Melatonin