Actions and pharmacokinetic properties of the alpha ...
|Title||Actions and pharmacokinetic properties of the alpha 2-adrenergic agents, medetomidine and atipamezole, in rainbow trout (Oncorhynchus mykiss)|
|Author(s)||T. Horsberg, J. Burka, R. Tasker|
|Journal||Journal of Veterinary Anaesthesia|
|Abstract||Medetomidine proved to be an effective sedative in rainbow trout but not an anaesthetic; its effects were antagonized by atipamezole. The clinical signs of medetomidine sedation were rapid settling to the bottom of the tank followed by progressive ataxia. The sedative effect was dose-dependent: at 1 mg/litre, 1 of 6 fish rested on its side after 10 min, whereas at 20 mg/litre all 6 rested on their sides. No loss of consciousness occurred. Atipamezole at 6 times the medetomidine concentration antagonized sedation. The average time before fish exposed to medetomidine alone showed avoidance reactions was 10 h, more than 5 times longer than the mean time in fish exposed to medetomidine and then atipamezole. During exposure to medetomidine (5 mg/litre) opercular movement rate decreased from 80/min to 20/min. The nature of opercular excursions also changed from being rapid and shallow to slow and deep. Respiratory movements increased after transfer to the bath containing atipamezole. Medetomidine had a marked effect upon skin colour, with fish becoming very pale a few min after exposure. Normal pigmentation was not restored until 4.5 days after exposure to medetomidine alone, but returned to normal after 10 min exposure to atipamezole solution. The half-life for medetomidine was 5.5 h and for atipamezole it was 8.6 h..|
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