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Metergoline and 5, 7-dihydroxytryptamine were found to suppress and to prevent an electroanalgesic effect, resp. An increase in the serotonine contents in the CSF after electroanalgesia suggests an activation of the brain serotoninergic system. DL-5-hydroxytryptophan and allopurinol enhanced the electroanalgetic effect. The data obtained suggests an existence of a serotoninergic component of the transcranial electroanalgesia mechanism.

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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.

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The selective lesion of the afferent serotoninergic system by means of intracisternal administration of 5,7-dihydroxytryptamine produces certain structural rearrangements in a part of cellular elements and in various parts of the neuropil of the neocortical parietal area. The deficiency of serotoninergic innervation influences the metabolic processes. This is evident from the change in the structure of protein synthesizing apparatus in a number of postsynaptic neurons. It is possible that the structural rearrangements observed in the serotoninergic and in the conjugated to it mediatory systems make the base of functional disorders in the neocortex and are accompanied with certain changes in the integrative activity of the brain.

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Owing to the microscopical investigation, using selective neurotoxin 5,7-dihydroxytryptamine, it has been possible to reveal the serotoninergic system and targets of its innervation in the rat cerebral cortex motor area. The serotoninergic axonal varicosities and synaptic boutons are present in all layers of the neocortex. Their large amount is revealed in the I and II layers. The terminals form contacts with dendrites of small size, sometimes they terminate on the head of the spines, as well as on bodies of neurons in different layers. According to their position and ultrastructural organization these neurons are, perhaps, pyramidal, that is glutamatergic, and those less in their size--refer to interneurons and can be GABAergic ones. Basing on own data and those of the literature, concerning the existence of nonsynaptic link for transmission of serotoninergic effects, a conclusion is made that a coordinating functioning of the synaptic and non-synaptic intercellular integrative mechanisms ensure a wide range of functions of the serotoninergic system in the cerebral cortex.

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Selective neurotoxic effect of 6-hydroxydopamine on the catecholaminergic systems was used to study the structural changes in the locus coeruleus and ventral tegmental neurons. Compared with the earlier published data on the blood-brain barrier permeability, the peculiarities of the responses of a part of neurons and synapses of the sites under study suggest that this selective catecholaminergic systems lesion leads to a decrease in their influence on the brain structures innervated. This causes impairment of inter-neurotransmitter relations and provide a morphological basis of various functional CNS shifts.

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Electron microscopy of rats ultrathin sections from dorsal and central raphe nucleus and spinal cord after 5,7-dihydroxytryptamine intracisternal microinjection (200 micrograms) has revealed neurones and axonal terminals distruction, which associated with tail-flick hypoalgesia and blood pressure nociceptive reactions diminished. In this condition the morphine (2 mg/kg) analgesia and drug depressive effect on pain hemodynamic manifestations increase significantly.

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Electron microscopical investigation of the ventral tegmental area at various time after administration of a specific neurotoxin 6-hydroxydopamine made it possible not only to reveal catecholamine reactive elements, but also those structural reorganizations in them, that are dependent on the lesion of the catecholaminergic systems, including certain changes in the receptor apparatus. Dark neurons with the change of different organelles preserve for a long time, up to 2.5 months. Reactive and destructive reorganizations of some axons, terminal buttons and postsynaptic poles of the ventral tegmental area are accompanied with certain functional disturbances, observed both experimentally and at a pathological process. The results of the work demonstrate that under conditions of the model experiments there is a possibility to study various stages of pathogenesis of a number of nervous-psychical diseases, connected or accompanied with disorders in certain mediator systems.

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Under the effect of electromagnetic radiation not any specific changes are revealed in the neural system unequivocally characterizing disturbances in its structure as a result of an excess absorption of electromagnetic energy. The ultrastructural changes revealed in the lateral fields of the cat hypothalamus are suitable for a well known scheme demonstrating the course of the pathological process, where three phases are distinguished: reactive, destructive and restorative. The pathological process develops gradually. The reactive changes in neurons and synapses, observed immediately after withdrawal of the electromagnetic action. increase during the following three months and result in coarse destructive disorders and in death of some neurons and synapses. In 6 months certain signs of restoration of the structures are observed. Under the effect of electromagnetic radiation water redistribution between the structures takes place, the sympathetic terminals loosing their fluid. Thus, certain conditions are produced for sticking together the synaptic vesicles. Possibly that deficiency of Ca++ ions contributes to it.

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Using light and electron microscopic examinations, the authors studied various portions of the rat brain following intracysternal administration of 6-hydroxydopamine. The lowered levels of noradrenaline in the cerebral tissue and an altered ultrastructure of neurons of the catecholaminergic centres and their processes were discovered in various areas of the brain. The time-course and the pattern of these readjustments may serve as a model for the investigation of the etiopathogenesis of various mental diseases and the elaboration of the methods of their pharmacotherapy.

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Construction and layer-by-layer distribution of catecholaminergic structures in the rat cortical parietal area have been studied electron microscopically. The method of 6-hydroxydopamine (6-OH-DA)-induced chemical rearrangements in the monoaminergic cerebral systems has been used. The intracisternal administration of 6-OH-DA (300 mcg) produces certain structural rearrangements in axons, their terminals and dendrites situating mainly in layers I, II, V and VI; within their limits the structural rearrangements are distributed unevenly. The catecholaminergic structures organization revealed is considered as a morphological base of varied functions of these systems.

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Ultrastructure of neurones and synapses of the cortical associative area of dogs has been studied under conditions of experimental neuroses caused by prolonged informational loads with constant time deficit and high motivational signals significance. Analysis of subcellular reorganization of a number of neuronal and synaptic organelles showed the degenerative changes of afferent conducting systems in various neuropil parts leading to the falling out of definite neuronal groups from stable functional connections and to the disturbance of intracortical interrelations. In the cortex simultaneously with destructive processes, are developing intracellular compensatory-adaptive reactions.

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Controlled and uncontrolled stimulation of the motor activity of 18-day chick embryo induces ultrastructural changes in sensomotor region of the archistriatum. These changes include the increase in the bulk of membrane structures, the increase of the area of presynaptic regions, the increase in electron density of microtubules and neurofilaments. Formation of a new adaptive behaviour is accompanied by an increase in the number of active synapses, which presumably accounts for adaptive plasticity of the brain in embryogenesis.

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