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 x 10(-6) M morphine in Tyrode solution at 37 degrees C, which was bubbled with 95% O(2) and 5% CO(2). 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 x 10(-6) M) contracted morphine-dependent ilea. Agmatine significantly inhibited the contractile response to naloxone in a dose-dependent manner (1 x 10(-7) M, 44%; 1 x 10(-6) M, 80%; 1 x 10(-5) M, 95%). This effect of agmatine was partly abolished by pretreatment with yohimbine and was almost completely abolished by idazoxan.
Aricioglu
Feyza
F
Department of Pharmacology, Faculty of Pharmacy, Marmara University, Istanbul, Turkey. feyzak@turk.net
Ercil
Eser
E
Dulger
Gul
G
D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology; D000376:Agmatine / Q000494:pharmacology*; D000701:Analgesics, Opioid / Q000378:metabolism; D000818:Animals; D004305:Dose-Response Relationship, Drug; D006168:Guinea Pigs; D019329:Idazoxan / Q000494:pharmacology; D007082:Ileum / Q000187:drug effects / Q000502:physiology*; D008297:Male; D009020:Morphine / Q000494:pharmacology; D009021:Morphine Dependence; D009119:Muscle Contraction / Q000187:drug effects*; D009270:Naloxone / Q000494:pharmacology*; D009292:Narcotic Antagonists / Q000494:pharmacology*; D013375:Substance Withdrawal Syndrome; D015016:Yohimbine / Q000494:pharmacology
D000317:Adrenergic alpha-Antagonists; D000701:Analgesics, Opioid; D009292:Narcotic Antagonists; D015016:Yohimbine; D009270:Naloxone; D000376:Agmatine; D009020:Morphine; D019329:Idazoxan