Effects of adrenoceptor agonists and antagonists on morphine-induced Straub tail in mice.
Straub-tail behavior was induced by subcutaneous injection of different doses (10-60 mg/kg) of morphine to mice. The maximum response was obtained with 20-40 mg/kg of the drug. The response induced by morphine (40 mg/kg) was decreased by intraperitoneal administration of different doses of clonidine (0.05-0.1 mg/kg). Pretreatment of animals with yohimbine (1-4 mg/kg i.p.) reversed the inhibitory action of clonidine. Yohimbine did not elicit any response by itself. Administration of prazosin (0.25, 0.5, and 1 mg/kg) reduced the morphine response. The combination of prazosin with yohimbine (1 mg/kg), but not with clonidine (0.05 mg/kg), caused a potentiated inhibition of the morphine effect. Phenylephrine (2-6 mg/kg i.p.) did not elicit any effect by itself and also did not alter the response induced by morphine or morphine plus clonidine. Dobutamine (2.5-10 mg/kg i.p.), atenolol (2.5-10 mg/kg i.p.), salbutamol (2.5-10 mg/kg i.p.), and propranolol (2.5-10 mg/kg i.p.) did not alter morphine-induced Straub-tail behavior in mice. In conclusion, activation of alpha2-adrenergic pathways contributes to morphine-induced Straub tail, while alpha1- and beta2-adrenergic may not be involved in this phenomenon.
Zarrindast
Mohammad-Reza
MR
Department of Pharmacology, Medical School, Tehran University of Medical Sciences, P.O. Box 13145-784, Tehran, Iran.
Ramezani-Tehrani
Banafsheh
B
Ghadimi
Maryam
M
D000322:Adrenergic Agonists / Q000494:pharmacology*; D018674:Adrenergic Antagonists / Q000494:pharmacology*; D000818:Animals; D004305:Dose-Response Relationship, Drug; D008297:Male; D051379:Mice; D009020:Morphine / Q000819:agonists / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D011941:Receptors, Adrenergic / Q000502:physiology*; D013623:Tail / Q000187:drug effects* / Q000502:physiology
D000322:Adrenergic Agonists; D018674:Adrenergic Antagonists; D011941:Receptors, Adrenergic; D009020:Morphine