Objective: To stably co-express
rat μ
opioid receptor and
human imidazoline-1 receptor in mammalian cells. Methods: The cDNAs encoding rat μ opioid receptor and human imidazoline-1 receptor were stably transfected into
CHO cells using liposome. Radioligand binding
assay and cAMP accumulation assay were used to determine densities and functions of the
expressed receptors. Results: Rat μ opioid receptor (rMOR) and human imidazoline-1 receptor (hI 1R) were co-expressed in the CHO cells (CHO-μ/I 1). The K d and B max values were (0.24±0.02)nmol/L and (1.83±0.13) pmol/mg protein for rMOR in 3H-diprenorphine binding assay, and (3.72±0.25) nmol/L and (43.59±6.83) fmol/106 cells for hI 1R in 3H-clonidine binding assay, respectively. The expressed MOR inhibited forskolin-stimulated cAMP accumulation, and the expressed I 1R inhibited naloxone-precipitated cAMP overshooting in chronic morphine-treated cells. Conclusion: The model system of co-expressing MOR and I 1R in CHO cells is first established.
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