The effect of the novel alpha-2-adrenoceptor agonist naphthylmedetomidine on pulse rate, arterial blood pressure and sedation in rabbits

The aim of this study was to investigate the effect of a novel alpha-2-adrenoceptor (alpha(2)-AR) agonist, naphthylmedetomidine, on cardiorespiratory function and sedation in rabbits in comparison with medetomidine. Prospective, randomized, experimental trial. Forty-two chinchilla rabbits of both sexes, weighing 2.5-4.5 kg. The rabbits received 350 mu g kg(-1) naphthylmedetomidine (n = 21) or medetomidine (n = 21) intramuscularly according to a randomization scheme. Arterial blood pressure (AP), oxygen saturation of haemoglobin (SpO(2)), pulse rate (PR) and righting reflex were monitored for 20 minutes after injection. Both drugs significantly decreased PR. The effect of medetomidine was significantly greater than that of naphthylmedetomidine and was evident within 1 minute. The decrease in PR after naphthylmedetomidine administration first appeared after 4 minutes. Medetomidine decreased the SpO(2) after 3 minutes but there was no effect after naphthylmedetomidine. Medetomidine decreased the mean, systolic and diastolic AP within 5 minutes of administration but naphthylmedetomidine had no effect. The mean time to loss of righting reflex was 185 and 714 seconds after the administration of medetomidine and naphthylmedetomidine respectively. These results provide the first description of the effects of naphthylmedetomidine on cardiovascular and psychomotor functions in rabbits. Further work is required to reveal the anaesthetic sparing, analgesic or sedative effect of partial naphthylmedetomidine.