title: Antagonistic effects of atipamezole and yohimbine on medetomidine-induced diuresis in healthy dogs.
abstract: This study aimed to investigate and compare the antagonistic effects of atipamezole and yohimbine on medetomidine-induced diuresis in healthy dogs. Five dogs were used repeatedly in each of 8 groups. One group was not medicated. Dogs in the other groups received 20 microg/kg of medetomidine intramuscularly and, 0.5 h later, saline (as the control injection), 50, 100, or 300 microg/kg of atipamezole, or 50, 100, or 300 microg/kg of yohimbine intramuscularly. Urine and blood samples were taken 11 times over 24 h for measurement of the following: urine volume, specific gravity, and creatinine concentration; urine and plasma osmolality; urine and plasma concentrations of electrolytes and arginine vasopressin (AVP); and the plasma concentration of atrial natriuretic peptide (ANP). Both atipamezole and yohimbine antagonized the diuretic effect of medetomidine, inhibiting medetomidine-induced decreases in urine specific gravity, osmolality, and concentrations of creatinine, sodium, potassium, chloride, and AVP and reversing both the medetomidine-induced increase in plasma concentrations of sodium, potassium, and chloride and the medetomidine-induced decrease in the plasma AVP concentration. Atipamezole significantly stimulated ANP release. The antidiuretic action of yohimbine was more potent than that of atipamezole but was not dose-dependent, in contrast to the action of atipamezole. The effects of these drugs may not be due only to actions mediated by alpha(2)-adrenoceptors.
authors.affiliation: Laboratory of Veterinary Internal Medicine, Department of Veterinary Medicine, Faculty of Agriculture, Tottori University, Tottori 680-8553, Japan.
authors.forename: Md Hasanuzzaman
authors.initials: MH
authors.lastname: Talukder
authors.forename: Yoshiaki
authors.initials: Y
authors.lastname: Hikasa
authors.forename: Hajime
authors.initials: H
authors.lastname: Takahashi
authors.forename: Kanako
authors.initials: K
authors.lastname: Sato
authors.forename: Aya
authors.initials: A
authors.lastname: Matsuu
mesh_terms: D000316:Adrenergic alpha-Agonists / Q000494:pharmacology; D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology*; D000818:Animals; D019540:Area Under Curve; D001127:Arginine Vasopressin / Q000097:blood / Q000652:urine; D009320:Atrial Natriuretic Factor / Q000097:blood / Q000652:urine; D004231:Diuresis / Q000187:drug effects*; D004285:Dogs / Q000097:blood / Q000502:physiology* / Q000652:urine; D007093:Imidazoles / Q000494:pharmacology*; D008297:Male; D020926:Medetomidine / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D009994:Osmolar Concentration; D011897:Random Allocation; D013046:Specific Gravity; D015016:Yohimbine / Q000494:pharmacology*
chemical_list: D000316:Adrenergic alpha-Agonists; D000317:Adrenergic alpha-Antagonists; D007093:Imidazoles; C050701:atipamezole; D001127:Arginine Vasopressin; D015016:Yohimbine; D009320:Atrial Natriuretic Factor; D020926:Medetomidine