Comparison of the opioid activity of CAM and kappa agonists

CAM has been shown to produce opiate agonist and antagonist activities. Based on its potent agonist activity in rabbit vas deferens and the low potency of naloxone to antagonize its agonist effect in the guinea pig ileum and mouse vas deferens, CAM can be considered as kappa agonist. It is further supported by its diuretic effect and the estimated "apparent pA2" values with naloxone and Mr-2266BS. However, in the rabbit ear artery and cat nictitating membrane, ethylketazocine (EK) produced agonist activity, while CAM produced antagonist activity. Also, EK differs from CAM in mouse vas deferens in the presence of 4-aminopyridine. It is concluded, that CAM might be an agonist on kappa type (subtype) of opiate receptors, although its spectrum of activity was found to be different from EK or bremazocine.