Effects of ifenprodil tartrate on the autonomic, peripheral and central nerve system

Effects of ifenprodil tartrate, a potent vasodilator, on the autonomic, peripheral and central nerve system were studied in experimental animals. In isolated vas deferens of guinea pigs, the contraction in response to noradrenaline and sympathetic nerve stimulation was competetively antagonized by ifenprodil 10-7-10-5M (pA2: 7.69 against noradrenaline). Ifenprodil (50_??_1, 000μg/kg i. v.) inhibited the contraction of cat nictitating membrane and dog urinary bladder induced by sympathetic nerve stimulation. Ifenprodil (250_??_1, 000μg/kg i. v.) lowered adrenaline-induced lethality (ED50: 360μg/kg). The drug produced a hypermotility of guinea pig uterus, and showed a transient hypertonus of dog gut which was abolished by atropine. Ifenprodil (10_??_20mg/kg i. v.) inhibited the propulsion of charcoal meal in mice. In Shay rats, more than 10mg/kg i. m. of the drug inhibited the secretion of acid gastric juice and the ulceration. Ifenprodil showed a potent local anesthetic action in the guinea pig cornea and skin. The spontaneous EEG of rabbits showed a resting pattern (0.25_??_2mg/kg i. v.) followed by an arousal pattern (5_??_10mg/kg). Ifenprodil (20_??_100mg/kg p. o.) potentiated a hypnosis induced by barbital, and potentiated pentylenetetrazol, strychnine and picrotoxin induced convulsion. The drug (20 and 100mg/kg p. o.) lowered the body temperature of rats. From these results it is concluded that ifenprodil produces a blocking action of α-adrenoceptors in various smooth muscle preparations and a direct relaxation of the smooth muscle itself without affecting the motor and central nerve systems.