[Effects of E2078, a new dynorphin derivative, on pituitary-adrenocortical functions in dogs]

E2078, a new analgesic is a dynorphin derivative. E2078 shows strong affinity to kappa receptors and is not rapidly cleaved by peptidases. This analgesic is also considered to be free of tolerance and dependence. In the present study, to determine the effect of E2078 on pituitary-adrenocortical function the author administered E2078 (0.001, 0.05, 0.1, 1.0, 10.0 mg.kg-1) by intramuscular injection to 38 adult mongrel dogs under enflurane anesthesia (1.0%) and then investigated the changes in the plasma concentrations of ACTH, cortisol, beta-endorphin, PRA, aldosterone and ADH. In the animal groups which received E2078 at dosages of 0.001, 0.05, 0.1, and 1.0 mg.kg-1, no significant differences in the plasma concentrations of each hormone were detected compared with the control group which received physiological saline by intramuscular injection. However, in the dog group which received E2078 at 10.0 mg.kg-1, the plasma concentrations of PRA and aldosterone were significantly elevated.