Fig. 3. Effects of different naloxone doses in α^2C-adrenoceptor knock-out mice. Thermoregulatory threshold temperatures after administration of saline (Sal), meperidine (Mep), saline plus 125 μg/kg naloxone (Sal+N125), saline plus 1,250 μg/kg naloxone (Sal+N1250), meperidine plus 125 μg/kg naloxone (Mep+N125), and meperidine plus 1,250 μg/kg naloxone (Mep+N1250) in α^2C-adrenoceptor knock-out mice (n = 10). Data are presented as mean ± SD. *  P < 0.05  vs. saline.