A) Nalbuphine and salvinorin A, full agonists of kappa opioid receptors, concentration dependently activate the G protein in the presence of kappa receptor. Dezocine fails to induce any G protein activation, indicating receptor antagonism. Based on the activity of the G protein in its presence, nor-binaltorphimine is an inverse agonist of kappa opioid receptor. B) G protein was pre-activated with a full agonist (Nalbuphine, 250 nM or Salvinorin A, 20 nM) and then increasing amounts of dezocine was added. Dezocine inhibited the agonist effects of nalbuphine and salvinorin A concentration-dependently with a total blockage at high concentration, confirming the kappa receptor antagonism effect of dezocine. The relationship is plotted using the following model: Y=Bottom + (Top-Bottom)/(1+10^((LogEC50-X)*HillSlope)).