Differential effects of sodium on two types of opiate binding sites (original) (raw)

High affinity binding of opiates to nervous tissue _ia vitro has been shown with several opiate agoniets and antagonists. In a previous study (1), we have shown that nalozone has at least two saturable binding sites, one of which is not available to an agoniat, dihydromorphina. This naloaone-specific binding site is the major fraction of opiate binding in the cerebellum but is a minor fraction in the thalamus-hypothalamus in which a predominant fraction of the opiate binding sites is capable of binding both aaloxone and dihydromorphine. These two types of opiate binding sites differ in their affinity for dihgdromorphiae and naloxone. In the present study, quantitative differences between these two ty~es of opiate b+nding sites were further explored by their response to Na , since the Na effect is one of the distinguishing characterietica of opiate binding to brain tissue in vitro (2-4) .