SPECIFIC, HIGH-AFFINITY [H-3]ETHYLKETOCYCLAZOCINE BINDING IN RAT CENTRAL NERVOUS-SYSTEM - LACK OF EVIDENCE FOR KAPPA-RECEPTORS

  • 1 January 1980
    • journal article
    • research article
    • Vol. 214  (3) , 516-519
Abstract
The binding properties and distribution of the tritiated benzomorphan, [3H]ethylketocyclazocine, were studied in rat CNS. Specific binding is saturable and represents 75-90% of total binding. Scatchard analysis is consistent with the existence of 2 classes of binding sites with Kd values of 0.5 and 10.5 nM, respectively. Ethylketocyclazocine binding is increased in the presence of NaCl. This characteristic resembles that of opiate antagonists rather than that of other agonists. The distribution of binding in rat CNS follows closely that seen with other opiate ligands. The IC50 [median inhibitory concentration] values of various opioid agonists and antagonists for competition with [3H]ethylketocyclazocine correlate well with their IC50 values for competition with [3H]naloxone. The existence of a separate .kappa. receptor in rat CNS is not supported.