In both rat brain and heart, noradrenaline and 5-hydroxytryptamine are metabolised predominantly by monoamine oxidase-A. The Km values for 14C-noradrenaline in the rat brain and heart are 290 microM and 300 microM, respectively, whereas for 14C-5-hydroxytryptamine the values are 180 microM and 140 microM, respectively. In the rat brain, mixed substrate experiments suggested that 14C-noradrenaline and 14C-5-hydroxytryptamine are metabolised at the same active centre. Both substrates are inhibited with similar Ki values by the reversible inhibitors cimoxatone, toloxatone and MD 770222.
Animals Brain