Some properties of brain opioid receptors in membrane bound and solubilized state

In brain membrane preparations, 3H-naloxone binding to bullfrog brain gave the highest values versus other species such as carp, chicken, rat and mouse. Scatchard analysis revealed that the Bmax value of bullfrog brain membranes was three fold greater than that of rat brain membranes. Opioid receptors were solubilized from bullfrog brain membranes using digitonin or 3-(cholamidopropyl)-dimethylammonio-1-propane sulfonate (CHAPS) as the detergent. The properties of solubilized opioid receptors were essentially the same as membrane bound receptors with regard to sensitivity to various treatments. The order of potency for a series of agonists in displacing 3H-naloxone binding in both membrane and solubilized preparations was bremazocine greater than pentazocine greater than morphine greater than delta-receptor peptide. Partial purification of opioid receptors was performed using a fast protein liquid chromatography system. Specific binding activity of 3H-naloxone was increased 10-15 fold within 20 min using the Mono Q column.