Agmatine Inhibits Naloxone-Induced Contractions in Morphine-Dependent Guinea Pig Ileum
This study investigates the effects of agmatine on naloxone-precipitated withdrawal syndrome in morphine-dependent guinea pig ileum. Male guinea pigs that were starved for 24 hours were decapitated after cervical dislocation, and terminal portions of the ilea were removed. Segments were fixed at a resting tension of 1 g in an organ bath containing 1 3 1026 M morphine in Tyrode solution at 378C, which was bubbled with 95% O2 and 5% CO2. Tissues were incubated in morphine containing Tyrode solution for 4 hours before agmatine was added. Naloxone and agmatine had no effect on naive ilea. Naloxone (1 3 1026 M) contracted morphine-dependent ilea. Agmatine significantly inhibited the contractile response to naloxone in a dose-dependent manner (1 3 1027 M, 44%; 1 3 1026 M, 80%; 1 3 1025 M, 95%). This effect of agmatine was partly abolished by pretreatment with yohimbine and was almost completely abolished by idazoxan.
agmatine morphine ileum imidazoline a2-adrenergic nmda nitric oxide