A method to determine dopamine levels and turnover rate in discrete dopamine nerve terminal systems by quantitative use of dopamine fluorescence obtained by Falck--Hillarp methodology.

In tissue sections of regions with evenly distributed dopamine (DA) nerve terminals such as the nucleus caudatus, it is possible to obtain absolute amounts (nmol/g) of DA by means of quantitative microfluorimetrical measurements of catecholamine (CA) fluorescence intensity in the tissue and in DA-containing albumin-agar standards. The values agree well with mass-fragmentographical determinations of DA. The steady-state DA levels of heterogenously innervated areas such as the tuberculum olfactorium determined by quantitative microfluorimetry can be made comparable to the steady-state levels of DA obtained by biochemistry in the entire tuberculum olfactorium by means of a conversion factor which considers the dilution of the DA-containing structures by non-DA-containing nerve cells in the biochemical analysis. This factor is obtained by making biochemical determinations in such regions of untreated animals (e.g. the tuberculum olfactorium). The results of this paper have demonstrated that the histochemical approach not only has a high power of resolution and makes it possible to perform studies on an intact morphological substrate but also allows the determination of DA steady-state (nmol/g) and DA turnover rate (nmol/g x min-1) in discrete DA nerve terminal systems of the brain in absolute amounts.