Effect of tizanidine on body temperature in the mouse

The effect of tizanidine [5-chloro-4-(2-imidazolin-2-yl-amino)-2,1,3- benzothiadiazole] on core temperature in the mouse was investigated in comparison with that of clonidine. Tizanidine decreased core temperature in unanaesthetized, freely-moving normal mice. Clonidine produced hypothermia in normal mice. The α₂-antagonist yohimbine produced an antagonism to tizanidine- and clonidine-induced hypothermia, while naloxone failed to antagonize the hypothermia. It is concluded that tizanidine and clonidine produce a similar hypothermic effect via an α₂-adrenoceptor, but not an endogenous opioid system.