Effects of clonidine and xylazine on body temperature in the rat

Clonidine and xylazine injected intraperitoneally both produced a dose-dependent hypothermia in unanaesthetized, freely moving rats. The alpha 2-antagonist yohimbine produced an antagonism of the xylazine-induced hypothermia but a potentiation of the clonidine-induced hypothermia. The opioid antagonist naloxone had little effect on the xylazine hypothermia, but potentiated the clonidine hypothermia. It is concluded that whilst the two alpha 2-agonists produce a similar hypothermic effect in the rat, they are acting by different mechanisms.