Antagonism of medetomidine-induced ataxia in rats by yohimbine, aminophylline and caffeine.
The actions of the alpha 2-antagonist yohimbine and methylxanthines aminophylline and caffeine were evaluated in reversing ataxia, increase in landing foot splay (LFS), produced by the alpha 2-agonist medetomidine in male rats. Medetomidine at 0.1 and 0.15 mg/kg, i.p. increased LFS by 42.9 and 69.6%, respectively. The peripherally acting alpha 2-agonist ST91 (0.125 to 0.5 mg/kg, i.p.) did not significantly affect the LFS. Intraperitoneal injection of yohimbine at 0.5 and 1 mg/kg, aminophylline at 25, 50 and 100 mg/kg, and caffeine at 25 and 50 mg/kg significantly antagonized medetomidine (0.15 mg/kg, i.p.)-induced ataxia. Yohimbine was more effective (100 and 111%) than the methylxanthines (28 to 72%) in reversing medetomidine ataxia. Aminophylline and caffeine, but not yohimbine, significantly reduced LFS in non-medetomidine treated rats. The data suggested that medetomidine ataxia in rats could be specifically antagonized by yohimbine and to a lesser extent by aminophylline and caffeine.
Mohammad
F K
FK
Department of Physiology, Biochemistry and Pharmacology, College of Veterinary Medicine, University of Mosul, Iraq.
Dawood
K A
KA
al-Dabbagh
S G
SG
D000316:Adrenergic alpha-Agonists / Q000037:antagonists & inhibitors*; D000628:Aminophylline / Q000494:pharmacology*; D000818:Animals; D001259:Ataxia / Q000139:chemically induced / Q000188:drug therapy; D002110:Caffeine / Q000494:pharmacology*; D003000:Clonidine / Q000031:analogs & derivatives / Q000037:antagonists & inhibitors; D006993:Hypnotics and Sedatives / Q000037:antagonists & inhibitors*; D007093:Imidazoles / Q000037:antagonists & inhibitors*; D008297:Male; D020926:Medetomidine; D051381:Rats; D015016:Yohimbine / Q000494:pharmacology*
D000316:Adrenergic alpha-Agonists; D006993:Hypnotics and Sedatives; D007093:Imidazoles; D000628:Aminophylline; D015016:Yohimbine; D002110:Caffeine; C011266:ST 91; D003000:Clonidine; D020926:Medetomidine