Normorphine hydrochloride was administered as a subcutaneous injection to male adult white volunteers as either a single 30 mg/kg dose or seven doses of 9 or 10 mg

μ-Opioid receptor (MOR) expressing 293T cells were homogenized in 5 mM Tris, 2 mM EDTA, pH 7.4 and centrifuged to extract the cell pellet. The pellet was resuspended in 50 mM of potassium phosphate buffer, pH 7.4. 20 micro-g of membrane protein was mixed with 0.1 - 1 nM of 3H-naloxone, 100 micro-M GTP and various concentrations of normorphine. Samples were incubated for 3 hours, then filtered through a glass fiber filter before liquid scintillation counting. The radioligand binding assay determined the initial affinity of normorphine for the μ-opioid receptor; a Ki of 0.063 μM was reported.