“Blockade of the …-adrenoceptors with yohimbine (0.5 mg/kg) which enhances the NA … to 486%, followed by 0.125 mg/kg fenoterol results in a further 2.53-fold rise to more than 1,200% … the basal level, indicating the pronounced counterregulatory role of the presynaptic α2-adrenoceptor.”
“However, after yohimbine (0.5 mg/kg) the evoked release was further enhanced by a much lower dosage of 0.125 mg/kg fenoterol to 450% of the control evoked release.”