High Resolution Radioautography of Noradrenergic Axon Terminals in the Neocortex
The existence of high affinity transport systems in the retina has been described for many substances being considered as neurotransmitters (for discussion, see van Gelder, this volume). These and other studies have demonstrated the usefulness of the “retinal model” for investigating biochemical properties of nervous tissue. They have also prompted several attemps to localise uptake sites by means of light microscope radioautography, in its highly ordered, though relatively simple cytoarchitecture (see Appendix I). However, no comparable investigations have yet been carried out at the electron microscopic level, despite the fact that tritiated dopamine, GABA and glycine, for example, which have been shown to be preferentially accumulated in certain cells of the retina, are also known to be retained in situ by the chemical fixation procedures required for high resolution radioautography. Thus, neither the fine structural features of the transmitter-containing elements, nor the intracellular distribution of the labelled neurotransmitters have been analysed in the retina, as in other parts of the central nervous system. The present report will therefore attempt to illustrate some of the principles and applications of high resolution radioautography in the identification and study of neuronal elements specified by their neurotransmitter content, using rat cerebral cortex as a model for the retina.
KeywordsNerve Ending Fine Structural Feature Endogenous Norepinephrine High Affinity Transport System Monoamine Neuron
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