Give examples of alpha2 agonists. Tolazoline, yohimbine, and atipamezole are alpha2 receptor antagonists used to neutralize the effect of alpha2 agonists. Atipamezole is used to reverse the effect of dexmedetomidine when necessary. Reference: Lamont, L. A.; Bulmer, B. J.; Sisson, D. D.; Grimm, K. A.; Tranquilli, W. J. Doppler echocardiographic effects of medetomidine on dynamic left ventricular outflow tract obstruction in cats. JAVMA, 2002; Nov. 1;221(9):1276-1281.