Ontogeny of monoamine oxidase A and B activities in developing chick cerebellum: a biochemical study

This study aims at characterizing the temporal evolution of MAO A and MAO B activities in developing chick cerebellum. In a first series of experiment s carried out in embryos at different stages and in one month-old chickens, we examined the inhibition dose-response curves obtained with clorgyline ( a selective inhibitor of MAO A) and l-deprenyl (a selective inhibitor of MA O B) using serotonin (5-HT) and beta-phenylethylamine (PEA) as substrates. The results obtained demonstrated that also in our system 5-HT was preferen tially deaminated by MAO A and PEA by MAO B. 5-HT and PEA were thus used in order to measure changes in MAO A and MAO B specific activities in cerebel la of embryos sacrificed daily from E10 until hatching (E21) and from one m onth-old chickens, In embryos at E10 MAO B activity was significantly highe r than MAO A activity. At subsequent stages MAO A and MAO B activities foll owed different patterns indicating different developmental regulation. The study of the kinetic parameters ( K-m and V-max) suggested that observed ch anges in enzyme specific activities mainly reflect variable enzyme amounts.