Páldyová Estera, Bereczki Erika, Sántha Miklós, Wenger Tibor, Borsodi Anna, Benyhe Sándor
Institute of Biochemistry, Biological Research Centre, Hungarian Academy of Sciences, Temesvari krt. 62, H-6726 Szeged, Hungary.
Neurochem Int. 2008 Jan;52(1-2):321-8. doi: 10.1016/j.neuint.2007.06.033. Epub 2007 Jul 4.
We examined the occurrence of possible changes in mRNA expression and the functional activity of opioid receptors after acute in vivo and in vitro treatment with the putative endogenous cannabinoid noladin ether. While noladin ether (NE) demonstrates agonist activity at CB1 cannabinoid receptors, recent data indicate that NE acts as a full agonist at CB2 cannabinoid receptors too. Considering the functional interactions between opioids and cannabinoids, it is of interest to examine whether NE affects the opioid system. To that end, we studied the influence of NE on mu-opioid receptor (MOR) mRNA expression and MOR mediated G-protein signaling. We used real-time PCR and [35S]GTPgammaS binding assays to examine the changes of MOR mRNA levels and the capability of the mu-opioid agonist peptide ([D-Ala2,(NMe)Phe4,Gly5-ol]enkephalin (DAMGO) in activating regulatory G-proteins via MORs in forebrain membrane fractions of wild-type (w.t., CB1+/+) and CB1 receptor deficient transgenic mice (knockout, CB1-/-). We found, that the expression of MOR mRNAs significantly decreased both in CB1+/+ and CB1-/- forebrain after a single injection of NE at 1 mg/kg when compared to control. Consequently, MOR-mediated signaling is attenuated after acute in vivo treatment with NE in both CB1+/+ and CB1-/- mice. Inhibition on MOR mediated activation is observed after in vitro NE administration as well. Radioligand binding competition studies showed that the noticed effect of NE on MOR signaling is not mediated through MORs. Both in vivo and in vitro attenuations of NE can be antagonized by the CB2 selective antagonist SR144528. Taken together, our data suggest that the NE caused pronounced decrease in the activity of MOR is mediated via CB2 cannabinoid receptors.
我们研究了用假定的内源性大麻素诺拉汀醚进行急性体内和体外处理后，阿片受体mRNA表达和功能活性可能发生的变化。虽然诺拉汀醚（NE）在CB1大麻素受体上表现出激动剂活性，但最近的数据表明，NE在CB2大麻素受体上也作为完全激动剂起作用。考虑到阿片类药物和大麻素之间的功能相互作用，研究NE是否影响阿片系统是很有意义的。为此，我们研究了NE对μ-阿片受体（MOR）mRNA表达和MOR介导的G蛋白信号传导的影响。我们使用实时PCR和[35S]GTPγS结合试验来检测野生型（w.t.，CB1+/+）和CB1受体缺陷转基因小鼠（敲除，CB1-/-）前脑膜组分中MOR mRNA水平的变化以及μ-阿片激动剂肽（[D-Ala2，（NMe）Phe4，Gly5-ol]脑啡肽（DAMGO）通过MOR激活调节性G蛋白的能力。我们发现，与对照组相比，单次注射1mg/kg的NE后，CB1+/+和CB1-/-前脑中MOR mRNA的表达均显著降低。因此，在CB1+/+和CB1-/-小鼠中，急性体内用NE处理后，MOR介导的信号传导减弱。体外给予NE后也观察到对MOR介导的激活的抑制。放射性配体结合竞争研究表明，NE对MOR信号传导的显著影响不是通过MOR介导的。CB2选择性拮抗剂SR144528可以拮抗NE在体内和体外的作用。综上所述，我们的数据表明，NE导致MOR活性显著降低是通过CB2大麻素受体介导的。
