Naloxone receptor action/selectivity

Most recently certain benzodiazepines have been discovered that fail to bind to sites typical of the class but with selective actions on subpopulations of opioid receptor dependent upon their substituents. One agent, tifluadom (54) acts selectively on x-receptors as judged by the usual criteria/1201 Thus tifluadon displaced the x-ligand 3H(-)-bremazocine from GP brain and inhibited GPI contractions with IC50 values intermediate between those of ketazocine and bremazocine, and was also active in the rabbit VD preparation (believed rich in x-sites). It was three times as potent as morphine in mice by the TF test and its action was more readily blocked by Mr 2266 than naloxone. It did not depress respiration in rats and had a low PDC in monkeys. 

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