Presence of delta opioid receptors on a subset of hypothalamic gonadotropin releasing hormone (GnRH) neurons.
Brain Res
; 1070(1): 15-23, 2006 Jan 27.
Article
em En
| MEDLINE
| ID: mdl-16405927
ABSTRACT
Opioid peptides exert an inhibitory effect on hypothalamic gonadotropin releasing hormone (GnRH) secretion mainly by interacting with mu-opioid receptors. Although a direct role for opioids via delta-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 delta-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 delta-receptors occurs on GnRH neurons and validates the use of GT1 cells to further investigate the nature of the DOR present on GnRH neurons.
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Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Hormônio Liberador de Gonadotropina
/
Receptores Opioides delta
/
Hipotálamo
/
Neurônios
Limite:
Animals
Idioma:
En
Revista:
Brain Res
Ano de publicação:
2006
Tipo de documento:
Article
País de afiliação:
Itália