Suppression by nor-binaltorphimine of kappa opioid-mediated diuresis in rats.

The effects of nor-binaltorphimine (nor-BNI) and beta-funaltrexamine (beta-FNA) were studied on the diuretic activities in rats of several kappa opioid agonists including ethylketazocine, tifluadom, bremazocine and U50,488H. Nor-BNI suppressed the diuretic activity of all kappa agonists, whereas beta-FNA failed to alter the diuresis. On the other hand, beta-FNA treatment completely blocked the morphine-induced antidiuresis, whereas nor-BNI had no effect. The present data add further evidence that nor-BNI is a highly selective antagonist of kappa opioid agonists.