[The ultrastructural manifestations of serotonin-deficient states in the neurons of the dorsal raphe nucleus].

: The ultrastructure of nucleus raphe dorsalis (NRD) and specific reactions of its elements were studied with a selective neurotoxin 5,7-dioxytriptamine under conditions of a primary selective injury of the serotonergic system. In this nucleus there are two groups of nervous cells reacting to the neurotoxin. The serotonergic terminal buttons are found throughout all the nucleus and are localized on part of dendrites with different diameters, on their spines and more rarely--on the bodies neurons. Most terminals in NRD do not form synaptic junctions but tightly adjoin different structures of its neuropil. The morphological findings concerning such functional contacts have shown that serotonin in NRD can influence through recurrent collaterals not only the proper serotonergic neurons, but also the activity of other cells in it and the targets of its innervation.