Phorbol ester differentially regulates oxytocin receptor binding activity in hypothalamic cultured neurons and astrocytes.
Hypothalamic cultured neurons and astrocytes were used to investigate the cellular mechanisms underlying the oxytocin receptor-mediated downregulation through a possible involvement of protein kinase C (PKC). For this purpose, the effects of PKC activators, inhibitor and of OT on OT receptor binding activity were compared in both cultures. In neurons, phorbol-myristate-acetate (PMA), a potent PKC activator, increased the binding of an OT receptor antagonist whereas in astrocytes, a decrease was observed. Pre-treatment of the cells with bisindolylmaleimide (10(-4) M), a PKC inhibitor, prevented the PMA-induced up- and downregulation. In contrast, receptor downregulation resulting from treatment of both cells with OT (10(-9) M) was not affected by the PKC inhibitor. On the other hand, when PMA (10(-7) M) was tested along with OT (10(-9) M), a subsequent decrease in ligand binding was observed in astrocytes. In neurons, PMA attenuated the OT-induced downregulation. Structural analysis of neuron and astrocyte OT receptor mRNA by RT-PCR, subcloning and sequencing, demonstrated identical sequence to rat uterine receptor. In conclusion, these data suggest that activation of PKC has opposite effect on OT receptor binding activity in neurons and astrocytes but they do not support the involvement of PKC in the OT-induced downregulation.
Strosser
M T
MT
Laboratoire de Neurophysiologie Cellulaire et Intégrée, UMR 7519, CNRS ULP, 21 rue René Descartes, 67084, Strasbourg Cedex, France.
Evrard
M E
ME
Breton
C
C
Guenot-Di Scala
D
D
D000818:Animals; D001253:Astrocytes / Q000187:drug effects / Q000378:metabolism; D015536:Down-Regulation / Q000187:drug effects*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D007031:Hypothalamus / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D007457:Iodine Radioisotopes; D009474:Neurons / Q000187:drug effects / Q000378:metabolism; D010121:Oxytocin / Q000494:pharmacology; D011485:Protein Binding; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism; D011869:Radioligand Assay; D051381:Rats; D018045:Receptors, Oxytocin / Q000378:metabolism*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*; D015854:Up-Regulation / Q000187:drug effects*
D004791:Enzyme Inhibitors; D007457:Iodine Radioisotopes; D018045:Receptors, Oxytocin; D010121:Oxytocin; D011493:Protein Kinase C; D013755:Tetradecanoylphorbol Acetate