The specificity of the pupillary actions of morphine and naloxone

Like many other opiates, morphine has a specific dose dependent mydriatic effect in mice which is antagonized by naloxone. In the present work we have studied the pupillary effects of the dextrorotatory isomers of morphine and naloxone, in comparison with the levorotatory active isomers. The dextrorotatory isomers lacked agonist and antagonist action, respectively. These results confirm that the pupillary effects of opiates are mediated through specific opiate receptors.