title: [3H]Etorphine binding activity in early chick embryos: brain and body tissue.
abstract: Stereospecific [3H]etorphine binding has been detected in chick embryos as early as day 4 of incubation in both brain and body tissue. By day 10 of incubation [3H]etorphine stereospecific binding activity is not detectable in nonneuronal tissue. The ubiquitous opiate binding sites early in embryogenesis are high affinity and respond to ion and GTP regulation in a manner similar to adult brain tissue. We interpret our observations to indicate all embryonic cells prior to cell differentiation contain opiate receptors. Therefore, we propose that opiate receptors play a dual role; one function early in embryogenesis not associated with neurotransmitter regulation, and another function later in embryonic development and in the adult: the classical neurotransmitter regulatory function.
mesh_terms: D000818:Animals; D001667:Binding, Competitive; D001921:Brain / Q000196:embryology* / Q000378:metabolism; D002454:Cell Differentiation; D002642:Chick Embryo; D005048:Etorphine / Q000378:metabolism*; D006160:Guanosine Triphosphate / Q000494:pharmacology; D007700:Kinetics; D008345:Manganese / Q000494:pharmacology; D009019:Morphinans / Q000378:metabolism*; D009928:Organ Specificity; D011957:Receptors, Opioid / Q000378:metabolism*; D012964:Sodium / Q000494:pharmacology
chemical_list: D009019:Morphinans; D011957:Receptors, Opioid; D005048:Etorphine; D008345:Manganese; D006160:Guanosine Triphosphate; D012964:Sodium