On the visualization of central dopamine and noradrenaline nerve terminals in cryostat sections.

Brain tissue from rats perfused with a mixture of glyoxylic acid and formaldehyde was frozen and sectioned in a cryostat. The cryostat sections were incubated in glyoxylic acid, dried and reacted with formaldehyde vapor. Using this technique cortical noradrenaline and dopamine containing nerve terminals could be visualized with high sensitivity in a reproducible way. The importance of several critical parameters was evaluated and it was found that the incubation of the cryostat sections in glyoxylic acid effectively inhibited the diffusion of catecholamines, particularly dopamine. Thus the fixation effect of glyoxylic acid was considered important besides the fluorophore formation. This modification of the Falck-Hillarp fluorescence technique is rapid, simple and reproducible and might be of value especially for quantitative measurements of the fluorescence.