Presence of delta opioid receptors on a subset of hypothalamic gonadotropin releasing hormone (GnRH) neurons
Autor: | Roberto Maggi, Tomas Hökfelt, Marco Parenti, Federica Pimpinelli, Francesca Guzzi, Flavio Piva |
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Přispěvatelé: | Pimpinelli, F, Parenti, M, Guzzi, F, Piva, F, Hokfelt, T, Maggi, R |
Rok vydání: | 2006 |
Předmět: |
DELTA OPPIOID RECEPTOR
endocrine system medicine.medical_specialty Enkephalin medicine.drug_class Hypothalamus Down-Regulation Hypothalamus Middle Gonadotropin-releasing hormone GTP-Binding Protein alpha Subunits Gi-Go Biology Gonadotropin-Releasing Hormone Rats Sprague-Dawley GTP-Binding Proteins Opioid receptor Receptors Opioid delta Internal medicine Cyclic AMP medicine Animals Tissue Distribution Opioid peptide Receptor Molecular Biology Cellular Senescence Cell Line Transformed Nerve Endings Neurons General Neuroscience Rats Endocrinology medicine.anatomical_structure Median eminence Neurology (clinical) Neuron Enkephalin D-Penicillamine (2 5) hormones hormone substitutes and hormone antagonists Developmental Biology |
Zdroj: | Brain Research. 1070:15-23 |
ISSN: | 0006-8993 |
Popis: | Opioid peptides exert an inhibitory effect on hypothalamic gonadotropin releasing hormone (GnRH) secretion mainly by interacting with μ-opioid receptors. Although a direct role for opioids via δ-opioid receptors (DORs) has been suggested, the presence of these receptors on GnRH neurons has never been demonstrated. In the present study, we determined the distribution of DORs in the basal hypothalamus of rat with special focus on their relation to GnRH neurons. Double-labelling immunofluorescence and confocal microscopy revealed that DORs are exclusively present in a subpopulation of GnRH nerve terminals, with the highest density in the external layer of the median eminence. We then studied the functional characteristics of DORs in an immortalized GnRH-secreting neuronal cell line (GT1-1) known to endogenously express this receptor. Here, pertussis toxin pretreatment abolished the δ-agonist (DPDPE) inhibitory effect on cAMP accumulation. We also analyzed the type of G proteins involved in the signal transduced by the DOR and showed that GT1-1 cells express the inhibitory Go and Gi2 alpha-subunits. However, only Go was down-regulated under chronic DPDPE exposure. Finally, since DOR is expressed postnatally in brain, we compared GnRH neuronal cells immortalized at different developmental stages (the more mature GT1-1 and GT1-7 cells, versus the more immature GN11 cells), evidencing that only mature neurons express DOR. In conclusion, our study indicates that a direct control of opioids via δ-receptors occurs on GnRH neurons and validates the use of GT1 cells to further investigate the nature of the DOR present on GnRH neurons. © 2005 Elsevier B.V. All rights reserved. |
Databáze: | OpenAIRE |
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