Incorporation of 18O2 into brain serotonin in vivo as a procedure for estimating turnover: a feasibility study in animals

Serotonin (5HT) containing 180 instead of 160 was found in brain after exposing rats to an atmosphere of 1802. The 180 incorporation appeared linear with time and 22% of the 5HT in striatum contained 180 after one hour of exposure. 180 entered 5HT by enzymatic reaction rather than by isotope exchange as treatment with p-chlorophenylalanine, to block tryptophan hydroxylase, prevented incorporation, while more 180-5HT than normal was found in brain after treatment with pargyline, to block monoamine oxidase. Our studies suggest that the incorporation of 1802 into brain 5HT might be a feasible approach for evaluating 5HT turnover in animals and with some modification might be applied in man.