Figure 2. The mu opioid receptor (MuOR) probe exhibits minimal cross-hybridization with control RNA samples. Slot blots were prepared with RNA from several transfected or untransfected cell lines. The A2b adenosine receptor (A2bR) and the melatonin 1 receptor (MelR) are two other members of the G-protein-coupled receptor superfamily. Blots were first hybridized to the MuOR probe (left). The exposure depicted for the COS-MuOR sample was 1 h, overlaid on an exposure lasting 24 h for all other samples. The positive signal for the COS-MuOR sample was grossly overexposed at 24 h. To confirm that similar amounts of RNA were loaded in each well, the blot was rehybridized (without stripping) to a cDNA probe for the human beta actin (right). All exposures were at -80 [degree sign] Celsius with one intensifying screen.