STABILIZATION OF HIGH-AFFINITY OPIOID AGONIST BINDING IN NEURAL CELL-MEMBRANES RIGIDIFIED BY CHOLESTEROL

Incorporation of cholesteryl hemisuccinate (CHS) into membranes from S H-SY5Y human neural cells increased membrane microviscosity at both su rface and core. In the rigidified membranes, mu-selective opioid agoni sts bound to a high-affinity state of the receptor similar to that obs erved upon receptor-G protein coupling. However, the high affinity sta te in rigidified membranes was unaltered by guanine nucleotides and pe rtussis toxin (PTX), and was not regulated by sodium. In contrast, the binding of opioid antagonists was insensitive to the membrane modific ation.