ABSTRACT
The antagonistic effect of the alpha 2-adrenoceptor antagonists atipamezole and yohimbine on medetomidine-induced sedation was studied in male Awassi sheep. The animals were sedated with an im injection of 40 micrograms medetomidine/kg bw. After recumbency, the sheep were injected iv with either 5 ml physiological saline solution (control), 0.2 mg atipamezole/kg or 0.2 mg yohimbine/kg. The saline-treated animals remained sedated and recumbent for 61.3 +/- 3.0 (mean +/- SE) min. Atipamezole or yohimbine significantly reduced the recumbency period to 2.8 +/- 0.9 or 4.3 +/- 0.9 min, respectively. Atipamezole or yohimbine significantly increased the medetomidine-induced reductions in the heart rate, respiratory rate and ruminal contractions. Rectal temperature was neither affected by medetomidine nor by the subsequent administrations of antagonists. These data suggest the usefulness of atipamezole or yohimbine in antagonizing the sedative effects of medetomidine in sheep.
Subject(s)
Hypnotics and Sedatives/antagonists & inhibitors , Imidazoles/antagonists & inhibitors , Imidazoles/pharmacology , Yohimbine/pharmacology , Adrenergic alpha-Antagonists/pharmacology , Animals , Drug Interactions , Hypnotics and Sedatives/pharmacology , Male , Medetomidine , SheepABSTRACT
The sedative effect of medetomidine was evaluated in 6 male Awassi sheep. Medetomidine at 40 micrograms/kg, i.m. induced sedation and recumbency in the sheep within 9 +/- 1 and 17 +/- 4 minutes, respectively. The duration of recumbency was 58 +/- 1 minutes. Medetomidine produced good analgesia and marked muscle relaxation in the recumbent animals for 30 to 45 minutes. The side effects of medetomidine were bradycardia, respiratory depression, stasis of the rumen with tympany, salivation and polyuria. The animals recovered from the sedative and side effects of medetomidine 1.5 to 2 hours after gaining the righting reflex without any apparent adverse effect. The results suggested that medetomidine could be a useful sedative analgesic in sheep.
Subject(s)
Analgesics , Hypnotics and Sedatives , Imidazoles , Sheep/physiology , Animals , Imidazoles/adverse effects , Male , Medetomidine , Muscle RelaxationABSTRACT
Male mice were treated orally with the organophosphorus insecticides fenamiphos and dichlorvos at 10 and 150 mg/kg, respectively. The insecticides produced signs of toxicosis characteristic of cholinesterase inhibition, and induced death in all treated mice. Pretreatment of mice with diphenhydramine HCl (20 and 30 mg/kg, subcutaneously) 15 min before either insecticide significantly (P less than 0.05) reduced the incidence of toxic manifestations (excessive salivation, Straub tail, and whole body tremor), delayed the onset of death, and increased the percentage of survivors. Doses of diphenhydramine less than 20 mg/kg were not so effective. The data indicated a protective property of diphenhydramine against organophosphorus insecticide-induced toxicosis.
Subject(s)
Dichlorvos/toxicity , Diphenhydramine/pharmacology , Insecticides/toxicity , Organophosphorus Compounds/toxicity , Animals , Cholinesterase Inhibitors/toxicity , Drug Antagonism , Male , Mice , Salivation/drug effects , Tremor/prevention & controlABSTRACT
Physostigmine (1.5 mg/kg, s.c.) and neostigmine (1.0 mg/kg, s.c.) injection into male mice produced signs of toxicosis characteristic of cholinesterase inhibition and evoked death in 95 and 94% of the animals respectively. Diphenhydramine injections (5-30 mg/kg, s.c.) 15 min before physostigmine or neostigmine significantly increased the latency period to onset of death and the percentage of survivors. Diphenhydramine injection (20 mg/kg, s.c.) between -30 and +2 min (but not at +5 and +10 min) relative to physostigmine prevented lethality in 100% of the animals. The data indicated that diphenhydramine which possesses anticholinergic effects protected mice against physostigmine- and neostigmine-induced toxicosis.
