[125I]SCH 23982, a new tool for rapid visualization of dopaminergic neurons in lower vertebrate retinas

Incubation of turtle or Xenopus retinas in 0.1 nM [125I]SCH 23982, a dopamine D1 receptor antagonist for 30-45 min and subsequent fixation in paraformaldehyde/glutaraldehyde resulted in strong blue formaldehyde-induced fluorescence of inner retinal neurons. On the basis of their morphological features, the labeled cells were classified as dopaminergic cells, an identification which was confirmed by double-labeling experiments using an antiserum against tyrosine hydroxylase. The whole experiment can be conducted in less than 2 h (whole mount), the label is very stable and allows the use of high-magnification objectives for detailed morphological investigation of dopaminergic retinal neurons.