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Autoradiographic localization of putative melatonin receptors in the brain of two old world primates: Cercopithecus aethiops and Papio ursinus
- Source :
- Università degli Studi di Padova-IRIS, Scopus-Elsevier, Università degli studi di Ferrara-IRIS
- Publication Year :
- 1993
- Publisher :
- Elsevier Science Limited:Oxford Fulfillment Center, PO Box 800, Kidlington Oxford OX5 1DX United Kingdom:011 44 1865 843000, 011 44 1865 843699, EMAIL: asianfo@elsevier.com, tcb@elsevier.co.UK, INTERNET: http://www.elsevier.com, http://www.elsevier.com/locate/shpsa/, Fax: 011 44 1865 843010, 1993.
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Abstract
- The distribution of putative melatonin receptors in the brains of two Old World primates of the superfamily Catarrhina, Cercopithecus aethiops and Papio ursinus, was characterized using 2-[125I]iodomelatonin autoradiography. The specific binding demonstrated a discrete distribution pattern. The median eminence was intensely labelled, and examination at the light microscopic level demonstrated that the binding was confined to the small layer of cells comprising the pars tuberalis of the pituitary gland. The collar of pars distalis, present in the baboon (Papio ursinus), was diffusely labelled. No binding was detected in the pars distalis proper or the neural lobe of the pituitary gland. The binding in the suprachiasmatic nuclei was weaker, but well discernible. Diffuse faint specific binding was found in the frontal cortex and the dentate gyrus of the hippocampus. Two non-neural sites expressed strong, well-delineated binding: the walls of some brain blood vessels (the vertebral and spinal arteries, the inferior cerebellar and acoustic arteries, the basilar, pericallosal, internal carotid arteries, the arteries forming the circle of Willis) and the choroid plexuses. Binding in the arteries of the circle of Willis, the pars tuberalis and the suprachiasmatic nuclei was readily displaceable. Addition of 1 microM unlabelled 2-iodomelatonin following 45 min of preincubation with the radioactive ligand completely abrogated the binding. Co-incubation with guanosine 5'-O-(3-thiotriphosphate) led to a significant decrease in the apparent binding density in the pars tuberalis and abolished binding in the suprachiasmatic nuclei, but was without effect on the binding in the walls of the adjacent arteries, forming the circle of Willis, in the cortex and in the hippocampus. This qualitative distribution pattern demonstrates that in the two primate species studied, melatonin high-affinity, G-protein-linked binding sites are present in the pars tuberalis and the hypothalamic suprachiasmatic nuclei, and that melatonin may be acting as a synchronizer of the endogenous pacemakers' circadian activity, apart from its possible reproductive effects at the level of pars tuberalis, where the highest receptor density was observed. The strongly labelled arterial walls, and the flimsy labelled cortex and hippocampus, expressed different characteristics: though the binding was readily reversible, it was apparently not regulated by a guanine nucleotide-binding protein.
- Subjects :
- Male
Pituitary gland
medicine.medical_specialty
Receptors, Melatonin
Hippocampus
Socio-culturale
Biology
Binding, Competitive
Melatonin
Internal medicine
Cortex (anatomy)
Chlorocebus aethiops
medicine
Animals
Neurotransmitter metabolism
Brain Chemistry
General Neuroscience
Brain
Ligand (biochemistry)
Receptors, Neurotransmitter
medicine.anatomical_structure
Endocrinology
Guanosine 5'-O-(3-Thiotriphosphate)
Pituitary Gland
Median eminence
Autoradiography
Female
Pars tuberalis
Papio
medicine.drug
Subjects
Details
- Database :
- OpenAIRE
- Journal :
- Università degli Studi di Padova-IRIS, Scopus-Elsevier, Università degli studi di Ferrara-IRIS
- Accession number :
- edsair.doi.dedup.....21fd162866f2192220a8bd816099ed08