The δ-Opioid Receptor in SK-N-BE Human Neuroblastoma Cell Line Undergoes Heterologous Desensitization |
| |
Authors: | Noureddine Namir,Jocelyne Polastron,Sté phane Allouche,Ahmed Hasbi, Philippe Jauzac |
| |
Affiliation: | Laboratoire des Neurosciences, CNRS URA 1829, Universitéde Caen, Caen, France |
| |
Abstract: | Abstract: The human neuroblastoma cell line SK-N-BE expresses δ-opioid receptors negatively coupled to adenylyl cyclase. Prolonged treatment (2 h) of the cells with 100 n M etorphine leads to an almost complete desensitization (8.2 ± 5.9 vs. 45.8 ± 8.7% for the control). Other receptors negatively coupled to adenylyl cyclase, namely, D2-dopaminergic, α2-adrenergic, and m2/m4-muscarinic, were identified by screening of these cells, and it was shown that prolonged treatment (2 h) with 1 µ M 2-bromo-α-ergocryptine or 1 µ M arterenol resulted in a marked desensitization of D2-dopaminergic and α2-adrenergic receptors, respectively. Cross-desensitization experiments revealed that pretreatment with etorphine desensitized with the same efficiency the δ-opioid receptor and the D2-dopaminergic receptor, and pretreatment with 2-bromo-α-ergocryptine also desensitized both receptors. In contrast, pretreatment with etorphine desensitized only partly the α2-adrenergic receptor response, whereas pretreatment with 1 µ M arterenol partly desensitized the δ-opioid receptor response. It is concluded that the δ-opioid receptor-mediated inhibitory response of adenylyl cyclase undergoes heterologous desensitization, and it is suggested that δ-opioid and D2-dopaminergic receptors are coupled to adenylyl cyclase via a Gi2 protein, whereas α2-adrenergic receptor could be coupled to the enzyme via two G proteins, Gi2 and another member of the Gi/Go family. |
| |
Keywords: | δ-Opioid receptor D2-dopaminergic receptor α2-Adrenergic receptor Heterologous desensitization |
|
|