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A neurotoxin 6-hydroxydopamine (6-OHDA) was introduced to 1, 2 and 3 day old male Wistar rats. Falck-Hillarp histochemical fluorescent method was used to analyze hypothalamic and hypophysial structures containing catecholamines. Statistically reliable decrease in catecholamine fluorescence intensity in hypothalamus and hypophysis, accumulation of catecholamines in nerve cells of supraoptic nucleus and in tanycytes of median eminence differed in 25- and 90-days rats. Disturbance of catecholaminergic systems of hypothalamus and hypophysis induced by neonatal introduction of 6-OHDA leads to reliable relaxation of orienting reaction and deep violation of learning that becomes stronger with age.

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Open-field behaviour and emotionally differently reinforced learning were studied in male Wistar rats with bilaterally ablated Locus coeruleus. Histochemical analysis of the hypothalamic structures was carried out. Decrease of investigating activity and attention was found as well as disturbances of learning with emotionally-negative (painful) reinforcement. By means of histochemical methods, fluorescence characteristic for catecholamines was found to decrease sharply in paraventricular and supraoptic hypothalamic nuclei, eminentia medialis and the posterior lobe of the hypophysis.

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For 6 months the rats were kept on 20 degrees ethanol. Then, the rats could choose whether to drink alcohol (A) or water. The rats formed 2 groups: those preferring A and those preferring water. The control rats were kept on water. The function of hypothalamus monoamine- and peptidergic systems were disturbed following chronic A treatment. Alcohol-preferring, unlike water-preferring rats, have revealed higher hypothalamus levels of serotonin and lower levels of dopamine and noradrenaline, which correlated with changes in fluorescence intensity of hypothalamus noradrenaline structures and were accompanied by remarkable disturbances in nonapeptide neurohormone transport in the paraventricular nucleus region.

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Falk's histochemical fluorescent method was used to study monoamine (MA)-containing structures in isolated hypothalamus nuclei and in the neurohemal region of the medial eminence (ME) in 40 male rats under the conditions of a long-term stress (6 months) which was caused by a repeated weak electrodermal stimulation. A statistically significant decrease in the intensity of MA fluorescence in the early period of the experiment, particularly significant in the fibers of the paraventricular nucleus and in the ME, was replaced by an increase in the intensity of MA fluorescence in the fibers and perikaryons in the arcuate paraventricular nuclei and in the ME on the 100th day. On the 180th day of the experiment MA fluorescence in the hypothalamus structures of the experimental and control rats did not differ significantly. Thus MA in the hypothalamus nuclei and ME were involved in adaptation processes of the body to chronic stress action. Changes of the MA content were particularly marked in the paraventricular nucleus, associated with cortical RH and vasopressin production as well as in the arcuate nucleus and in the ME associated with the entry of these hormones in the hypophysial portal vessels to regulate ACTH secretion.

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The posterior neurohypophysis (PNH)-pars intermedia complex of the wild and pond carp, Cyprinus carpio L., has been studied by light, fluorescence and electron microscopy. "Gomori-positive" neurosecretory fibres are abundant in the main trunk of the neurohypophysis as well as its roots penetrating the pars intermedia. Terminals of these fibres are in contact with capillaries of the general circulation and with glandular cells of the pars intermedia. Monoaminergic fibres with a weak green fluorescence, somewhat increasing after injection of nialamide into the pond carp, have largely the same distribution. Three types of neurosecretory fibres and their terminals have been recognized in the PNH-pars intermedia complex. Types-A1 and -A2 fibres, containing granules of 140-180 nm and 100-160 nm in diameter respectively, are peptidergic "Gomori-positive". Type-A2 fibres predominate in the PNH. The least frequent monoaminergic type-B fibres have granules of 60-100 nm in diameter. Numerous peptidergic and few monoaminergic neurosecretory terminals make contact with the capillaries located within the roots of the PNH as well as at the border between them and the pars intermedia. Both peptidergic and monoaminergic terminals make direct synaptoid contacts with the gland cells or end close to connective tissue septa, basal lamina or pituicytes. The PAS-positive gland cells and to a lesser degree the lead-haematoxylin-positive gland cells show these relationships with neurosecretory terminals. The question concerning the mode of interaction between peptidergic and monoaminergic structures in the dual control of the gland cells of the pars intermedia of teleosts is discussed.

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"Falck-positive" monoaminergic neurosecretory cells (M-NSC) are found in stage I-II sturgeon larvae in the dorsal zone of the preoptic nucleus (PN) by means of fluorescence and electron microscopy. Single poorly differentiated M-NSC are located mostly among the ependymal cells. At this stage the M-NSC have very short dendrites protruding into the third ventricle. In the process of differentiation the M-NSC move subependymally and their dendrites become longer. Axons of the M-NSC can be clearly traced only in stage IV larvae. Perikarya and dendrites of M-NSC contain little rough endoplasmic reticulum and numerous neurosecretory granules (NSG) 60-150 nm in diameter. Ventricular dendrites of the "Gomori-positive" peptidergic neurosecretory cells (P-NSC) containing NSG 110-200 nm in diameter are observed within the PN in stage III larvae. Thus the M-NSC differentiate earlier than the P-NSC. The intraventricular terminals have kinocilia and show typical macroapocrine secretion. This fact supports the view of a receptory as well as a secretory function of the M-NSC and P-NSC. It is proposed that in early ontogeny monoamine as well as peptide neurohormones are secreted into the cerebrospinal fluid. This transventricular pathway is considered phylogenetically ancient.

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The effect of pharmacological destruction of hypothalamic monoaminergic terminals on the basal and cold stress-induced secretion of neurohormones of the sympathoadrenal system (SAS) in rats was studied. The data obtained on biochemical and histochemical analysis of the hypothalamus (dopamine, noradrenaline and serotonin level, the picture of catecholaminergic terminal fluorescence) were compared with adrenaline and noradrenaline content in blood. It is assumed that function of the SAS is inhibited by hypothalamic noradrenaline and stimulated by dopamine and serotonin under cold stress.

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The proximal neurosecretory contact region (PNCR) of the lamprey, a homologue of the median eminence of tetrapods, was studied by light, fluorescence and electron microscopy. Paraldehyde fuchsin-positive neurosecretory fibers are seen mainly in the central part of the rostral subdivision of the PNCR. The Falck-Hillarp technique reveals a weak, mainly diffuse yellow-green fluorescence in the PNCR. The ultrastructure of the tanycyte layer of the PNCR is very similar to that in the neurohypophysis of the same species, although the funnel-shaped protrusions of the third ventricle in the rostral part of the PNCR are more frequent than in the neurophypophysis. Peptidergic A1 and A2 neurosecretory fibers are characterized by neurosecretory granules of 120-200 nm and 100-150 nm in diameter, respectively. Monoaminergic B type fibers contain granules 80-100 nm in diameter. Neurosecretory terminals and the vascular endfeet of tanycytes make contact with the basement membrane of the avascular connective tissue layer separating the PNCR from the hypophysial pars distalis. It is suggested that both peptide and monoamine neurohormones diffuse through the thick connective tissue septa into the underlying blood vessels which supply the pars distalis and thus affect the function of its glandular cells.

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The content and distribution of norepinephrine in the hypothalamus following acute and chronic alcohol opisoning of animals (by introducing of a 20 degrees alcohol by mouth) was studied by applying biochemical and flurorscence histochemical methods. After poisoiing the content of neorpinephrine in the hypothalamus increased twice as compared with controls and continued to be high for 3 months. This was attended by a greater fluorescence intensity in the noradrenergic fibres, in the areas of the hypothalamic supra-optic nuclei and an inhibition of the transport and release of the neurosecretory material in the supra-optic neurohypophysial system was observed. And, conversely, 6--8 months after poisoning the content of neorpinephrine was halved in comparison with the controls.

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The proximal neurosecretory contact region (PCR) of Acipenseridae, a homologue of the tetrapod median eminence, has been studied by light, fluorescence and electron microscopy. It occupies the rostral and chiefly the ventral surfaces of the hypothalamic tuber cinereum. PAF-positive fibres occur in the zone of the preoptico-hypophysial tract but their terminal enlargements are concentrated mainly in the external zone. They make contact with the primary portal capillaries situated in the pia mater. Monoaminergic fibres and terminals with an intense green fluorescence are localized in the same regions. The fibres of some bipolar monoaminergic neurons of the PCR make contact both with the third ventricle and the primary portal capillaries. Three types of granule-containing neurosecretory fibres and terminals have been recognized in the PCR. Fibres of types A1 (d = 120-300 nm) and A2 (D = 100-170 nm) are peptidergic PAR-positive, although some fibres, including some of type A1, belong possibly to PAF-negative type. Monoaminergic type B fibres have granules 80-100 nm in diameter. Neurosecretory terminals and vascular "endfeet" of tanycytes make contact with the 70 nm thick outer basement membrane of the primary portal capillaries. Several laminae of thin horizontally oriented tanycyte processes form a boundary between the external zone and the preoptico-hypophysial tract. Few neuroglial cells with pale cytoplasm, numerous lysosomes and lipofuscin granules are seen in this region. It is hypothesized that, as in other vertebrates both peptide hypophysiotropic neurohormones and monoamines are discarged from the PCR into the portal circulation and affect the activity of the glandular cells of the pars distalis.

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Monoaminergic fibres exhibiting green fluorescence have been revealed by the Falck histochemical fluorescence technique in the area of the hypothalamic preoptic nuclei and nucleus lateralis tuberis of the carp. Monoaminergic cerebrospinal fluid-contacting nerve cells with an intensive greenish and yellowish fluorescence were observed in the walls of the lateral and posterior recesses of the third ventricle. Monoaminergic fibres are few in the pro-and meta-adenohypophysis. Yellowish-green fluorescent fibres seem to be much more frequent in the meta-adenohypophysis. Fluorescence of the fibres is unstabel and of a weak intensity.

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Distribution of adrenergic and peptidergic nerve fibers in rat median eminence was studied three weeks after bilateral adrenalectomy. Fluorescence intensity in the external zone and in some of the nerve cell-bodies proved to be increased in the nucleus arcuatus. There were many nerve fibers with a bright fluorescence in the internal zone. A great number of the peptidergic nerve fibers appeared in the external zone. Reactions in the rostral, medial and caudal regions of the median eminence differed and were described.

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