Opiate receptor: cooperativity of binding observed in brain slices.

Abstract
Kinetic constants for binding of 3H-labeled morphine and naloxone were determined from Hill plot analyses and from experiments in which the concentration of tritiated drug was constant and that of nonlabeled drug varied. With [rat] brain slices, the binding of either drug exhibited strong positive cooperativity (Hill slope > 3); this was not observed in brain homogenates. In slices the relationship between opiate binding site and ligand may be more relevant physiologically and pharmacologically.