Effects of tolazoline and yohimbine on xylazine-induced central nervous system depression, bradycardia, and tachypnea in sheep.
We compared the ability of tolazoline and yohimbine to antagonize xylazine-induced central nervous system depression, bradycardia, and tachypnea in 9 ewes and 5 rams. Once a week for 3 weeks, each sheep received one IV treatment of 0.4 mg xylazine/kg, 0.4 mg xylazine/kg followed in 10 minutes by 2 mg tolazoline/kg, or 0.4 mg xylazine/kg followed in 10 minutes by 0.2 mg yohimbine/kg. The order of the 3 treatments in each sheep was randomized. Xylazine alone caused recumbency for 41.0 +/- 3.7 minutes (mean +/- SEM). Tolazoline and yohimbine shortened the xylazine-induced recumbency to 12.1 +/- 0.9 minutes and 18.1 +/- 1.5 minutes, respectively. Sheep given xylazine alone had head droop for 34.0 +/- 5.4 minutes after rising. Head drooping of sheep given tolazoline or yohimbine was reduced to 10.1 +/- 1.7 minutes and 14.2 +/- 1.7 minutes, respectively. Both tolazoline and yohimbine reversed the bradycardia and tachypnea that followed xylazine administration. No statistical differences in the rate and magnitude of the reversal were observed between the 2 drugs.
D000818:Animals; D001921:Brain / Q000187:drug effects; D005260:Female; D006339:Heart Rate / Q000187:drug effects; D008297:Male; D011897:Random Allocation; D012119:Respiration / Q000187:drug effects; D012756:Sheep / Q000502:physiology*; D013843:Thiazines / Q000037:antagonists & inhibitors*; D014043:Tolazoline / Q000494:pharmacology*; D014991:Xylazine / Q000037:antagonists & inhibitors* / Q000494:pharmacology; D015016:Yohimbine / Q000494:pharmacology*
D013843:Thiazines; D014991:Xylazine; D015016:Yohimbine; D014043:Tolazoline