Initial confinement of opiate receptors to the nervous system has recently been broadened to
several other cell types. Based on the well established hypotensive effect of morphine, we
hypothesized that endothelial cells may represent a target for this opiate substance.
Endothelial cells (human arterial and rat microvascular) contain a high affinity, saturable
opiate binding site presumed to mediate the morphine effects that is stereoselectively and
characteristically antagonized by naloxone. This opiate alkaloid-specific binding site is …