The noradrenergic innervation of the area postrema has been studied by means of immunofluorescent localization of dopamine-β-hydroxylase and with electron microscopy. This type of correlative study is effective because the immunofluorescent localization is highly specific and electron microscopy affords a resolution not possible with the fluorescent technique alone. Two distinct groups of noradrenergic cell bodies are found to be associated with the area postrema. The bulk of noradrenergic innervation appears to derive from those DBH containing cell bodies immediately adjacent to the area postrema. The distribution of axons originating from the other group of neurons, which are located within the area postrema, cannot be determined by these techniques since there are too many intertwined fibers in this part of the tissue. The noradrenergic nerve terminals assume two distinct patterns. In the ventral and lateral parts, the synapses are typical of the central nervous system, being axosomatic or axodendritic. The terminals of the superior margins are related to non-neural structures as in the peripheral nervous system and involve ependymal cells and perivascular smooth muscle.
Bibliographical noteFunding Information:
This work has been supported in part by U.S. Public Health Service Grants NS 08549 from the National Institute of Neurological Diseases and Stroke by MH 21874 and Research Scientist Award K2-70,451 from the National Institute of Mental Health.