Possible involvement of cerebroside sulfate in opiate receptor binding

Cerebroside sulfate (CS) appears to fulfill most of the structural requirements of a hypothetical opiate receptor. It possesses many of the properties that are thought to be necessary for the identification of an 'opiate receptor', exhibiting high affinity and stereoselective binding to a number of narcotic drugs. Although these properties are insufficient to establish identity of the receptor, it is highly significant that the affinity of this binding can be correlated with the analgetic potency of these drugs in both man and rodents. CS is an endogenous component of brain tissue, and a partially purified opiate receptor from mouse brain has been found to be CS. Other experiments indicate that reduced availability of brain CS decreases the analgetic effects of morphine and this is accompanied by a reduction in number of binding sites, suggesting that the interaction of opiates with CS observed in vitro may also have importance in vivo. CS was also found to be a component of the opiate receptor after marking with ¹²⁵I-labeled diazosulfanilic acid. The possibility that CS or the SO ₄ ^-2 group of this lipid may be the 'anionic site' of the opiate receptor should be considered.