A morphometric analysis of transmitter identified dendrites and nerve terminals

The present method is exemplified on coronal sections of the medulla oblongata containing phenylethanolamine-N-methyltransferase (PNMT) immunoreactive nerve cell bodies and their processes and on coronal sections of the pons containing the locus coeruleus, where PNMT immunoreactive nerve terminals have been demonstrated together with the dopamine-beta-hydroxylase immunoreactive nerve cell bodies. Morphometric analysis of the processes (both length and branches) and of the nerve terminals involve as a first step the division of the area under study into squares 100 microns wide, which are superimposed on a Cartesian plane. The uniformity of the density distribution of the nerve terminals and the processes (branches or length) can be analyzed by Lorenz curves, which in a quantitative way can measure the degree of unevenness and thus represent a measure of concentration. A concentration index can therefore be calculated. By the use of the densitometric approach it also becomes possible to study the density distribution of the nerve terminals with the highest antigen contents. The present method will make it possible to quantitate morphological changes occurring in processes and nerve terminals of transmitter-identified neurons.