Correlation between (abscissae) pKD values of antagonists at α2-autoreceptors in the adrenal medulla of wild-type mice, and (ordinates) pKD values at α2 binding sites in bovine pineal gland (a, d), neonatal rat lung (b, e) and opossum kidney (OK) cells (c, f), for noradrenaline (NA) (a, b, c) or adrenaline (AD) (d, e, f). Autoreceptor pKD values are from present experiments. Binding site pKD values are from Simonneaux et al. (1991) (a, d) and Blaxall et al. (1991) (b, c, e, f).