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The hypothalamus is the most important integrator of functions of the autonomous, endocrine, somatic nervous systems; it is involved in the regulation of rhythmic processes and systemic aging. Putative hypothalamic nuclei responsible for the implementation of the developmental program of aging include the suprachiasmatic nucleus and the median group of nuclei, including the arcuate, ventromedial, and dorsomedial nuclei. Hypothalamic aging is accompanied by an excitation–inhibition imbalance due to dysregulation of the GABAergic system, decreased frequency of neuronal firing, impaired calcium metabolism, elevated nitric oxide production, decreased autophagy, and disturbed intracellular signaling, in particular Sirt1, mTOR, NF-κB, AMPK, P53, and FoxO. Also, an important role in hypothalamic aging belongs to specialized ependymal cells, tanycytes, as manifested in the disruption of tanycyte-neuron relationships and impaired barrier function of these cells. Hypothalamic neural stem cells, located mainly in the region of the middle hypothalamic nuclei, secrete exosomal microRNA also responsible for anti-aging effects of stem cells. The pool of hypothalamic neural stem cells, as well as microRNA production therein, decline with age.

The calcium-binding protein parvalbumin is selectively expressed in various subpopulations of neurons in the central and peripheral nervous system. The localization and percentage composition of parvalbumin-immunoreactive neurons were determined in the metasympathetic enteric ganglia of the small and large intestine in rats of different ages (1, 10, 20, 30, and 60 days and two years). Parvalbumin-immunoreactive neurons were present in the intermuscular plexus during ontogeny, from birth to old age, and the percentage of these cells in the intermuscular plexus in the small intestine increased from day 10 to day 20 of life and in that of the large intestine in the first 10 days of life. Parvalbumin was absent from the submucous plexus of the small and large intestine in neonatal rats, but was present from day 10. The percentage of parvalbumin-immunoreactive neurons in the submucous plexus increased between day 10 and day 20 of life. On aging, the proportions of parvalbumin-immunoreactive neurons in the intermuscular and submucous plexuses did not change significantly. Thus, the proportion of parvalbumin-immunopositive neurons in the intramural intestinal ganglia increased in early postnatal ontogeny. This increase is probably associated with the buffer role of parvalbumin in relation to Ca2+ ions.

Objectives. To identify changes in the immunohistochemical characteristics of neurons in the arcuate (AN), ventromedial (VMN), and dorsomedial (DMN) nuclei of the hypothalamus in rats on aging. Materials and methods. Studies were performed using male Wistar rats aged 3–4 months (five individuals) and 12–18 months (five individuals) using immunohistochemical methods. Results. Aging was associated with a decrease in the relative content of calbindin-immunopositive neurons in the DMN, while calretinin-immunopositive neurons in the DMN and VMN increased. The numbers of neurons immunopositive for neuronal nitric oxide synthase and the level of immunofluorescence for this enzyme were greater in all the nuclei studied in older animals. Older rats also showed a higher density of neuropeptide Y-immunopositive fibers in the VMN, with a smaller number in the DMN. Conclusions. Aging was associated with changes in the neurochemical composition of neurons, mainly in the ventromedial and dorsomedial nuclei of the hypothalamus.

Sympathetic innervation of the stomach is carried out by the prevertebral ganglia of the solar plexus. The localization and neurochemical composition of neurons innervating the stomach in the postnatal ontogenesis of rats have been studied by the method of retrograde axon transport of Fast Blue. In all animals, the celiac ganglia had more labeled neurons than the superior mesenteric ganglion. The number of labeled neurons increased in the first ten days of life and then did not change until senescence. All labeled neurons innervating the stomach contain tyrosine hydroxylase, the catecholamine synthesis enzyme. The proportion of labeled neuropeptide Y-immunopositive neurons did not change during ontogeny; the percentage of labeled calbindin-immunoreactive neurons decreased in the first month of life.

Objectives. To determine the locations, percentage composition, and morphometric characteristics of sympathetic preganglionic neurons containing NO synthase (NOS) in the spinal cord of rats. Materials and methods. Experiments were performed on 35 white female Wistar rats aged 3, 10, 20, 30, and 60 days, 6 months, and 3 years. Immunohistochemical detection of NOS and the acetylcholine synthesis enzyme choline acetyltransferase (CAT) was performed on sections of spinal cord made at the level of segment T2. The areas of nerve cells and the proportions of immunoreactive neurons were determined. Results. Most sympathetic preganglionic neurons in the spinal cord of neonates and 10-day-old rats contained both NOS and CAT. At these age groups, rats also had a population of NOS-positive/CAT-negative neurons (26% in neonates and 8% in 10-day-old animals), this population was not seen in older animals. During the first 20 days, the proportion of NOS-immunopositive neurons decreased significantly, while the population of CAT-positive neurons increased. Conclusions. There was a reduction in the number of sympathetic preganglionic neurons expressing NOS during early postnatal ontogeny, which may influence the mechanisms of NO-ergic sympathetic transmission.

Sympathetic innervation of the stomach was studied in rats by the method of retrograde axon transport of Fast Blue in postnatal ontogenesis. The number of labeled neurons increased in the first 10 days of life and then did not change until the senescence. All labeled neurons innervating the stomach contain the catecholamine synthesis enzyme, tyrosine hydroxylase. The proportion of labeled neuropeptide Y-immunopositive neurons did not change in the development, the percentage of labeled calbindin-immunoreactive neurons decreased in the first month of life.

Sympathetic innervation of the stomach is carried out by the prevertebral ganglia of the solar plexus. The localization and neurochemical composition of neurons innervating the stomach in postnatal ontogenesis in rats was studied using the method of retrograde axon transport of Fast Blue. In all animals, the celiac ganglia had more labeled neurons compared to the superior mesenteric ganglion. The number of labeled neurons increased in the first 10 days of life and then did not change until the senescence. All labeled neurons innervating the stomach contain the catecholamine synthesis enzyme, tyrosine hydroxylase. The proportion of labeled neuropeptide Y-immunopositive neurons did not change in the development, the percentage of labeled calbindin-immunoreactive neurons decreased in the first month of life.Симпатическая иннервация желудка осуществляется превертебральными узлами солнечного сплетения. Методом ретроградного аксонного транспорта быстрого голубого (Fast Blue) исследовали локализацию и нейрохимический состав нейронов, иннервирующих желудок в постнатальном онтогенезе у крыс. У всех животных в чревных узлах выявляли больше нейронов, содержащих метку, по сравнению с краниальным брыжеечным узлом. Количество меченых нейронов возрастало в первые 10 сут жизни и далее не изменялось вплоть до старости. Все меченые нейроны, иннервирующие желудок, содержат фермент синтеза катехоламинов — тирозингидроксилазу. Доля меченых нейропептид-Y-иммунопозитивных нейронов не менялась в онтогенезе, доля меченых кальбиндин-иммунореактивных нейронов снижалась в первый месяц жизни.

Expression of neuronal NO synthase in the sympathetic cranial cervical ganglion and stellate ganglion in rats during postnatal ontogeny was studied by immunohistochemistry and Western blotting. In the sympathetic ganglia, neuronal NO synthase-immunoreactive neurons were absent in all rats. In the stellate and cranial cervical ganglia, the expression of neuronal NO synthase and the density of immunoreactive fibers increased in early postnatal ontogeny from the moment of birth to the age of 30 days and then decreased. Thus, we observed heterochroneous expression of neuronal NOS in the preganglionic somata in the spinal cord and in the preganglionic fibers in the sympathetic ganglia during ontogeny.

The expression of choline acetyltransferase (ChAT), neurofilament (NF) protein 200 kDa, calbindin (CAB) 28 kDa, neuronal NO-synthase (nNOS), caspase 3, Ki-67 was studied in motor neurons from TIII–TV segments of the spinal cord in C57/ BL6 male mice by immunohistochemical methods 12 h after a 30 days-long space flight on the Bion-M1 biosatellite. Mice living under standard vivarium conditions served as a control. The motoneurons of experimental animals demonstrated the reactive changes that were manifested by the increase of their size, decrease in the number of subpopulations expressing ChAT and NF, increase of subpopulations containing CAB, appearance of motor neurons expressing nNOS, caspase-3, and the absence of Ki-67. The lack of proliferating gliocytes, the preservation of nucleolar component indicate the absence of necrobiotic changes characteristic of necrosis. The cytoplasmic vacuolization was observed in thionine-stained CAB-immunoreactive neurons. The disintegration of motor neurons into fragments resembling the apoptotic bodies was observed in single cells that contained caspase-3.

Sympathetic ganglia consist of neurochemically and functionally distinct populations of neurons, characterized by a specific projection pattern and a set of neutransmitters including classical mediators (catecholamines and acetylcholine), neuropeptides and small molecules such as NO, H2S, CO. The majority of the principal ganglionic sympathetic neurons is noradrenergic and expresses tyrosine hydroxylase (TH), i.e., a key enzyme in catecholamine synthesis. In mammals, two third of catecholaminergic neurons also co-localizes neuropeptide Y. A small number of ganglionic sympathetic neurons contains enzyme of acetylcholine synthesis and some neuropeptides, such as somatostatin, vasoactive intestinal (poly)peptide (VIP), calcitonin gene-related peptide (CGRP). Acetylcholine-containing sympathetic neurons in most cases colocalize VIP and/or CGRP. Phenotype of autonomic neurons is regulated by both target-independent and target-dependent mechanisms. The most of transmitters are expressed during embryogenesis. TH appears during embryonic development and the percentage of TH-positive neurons remains virtually identical during ontogenesis. After birth, cholinergic neurons exhibit a noradrenergic phenotype. Expression of different neuropeptides changes in pre- and postnatal development. Neurotransmitter expression in sympathetic neurons is influenced by growth factor signaling via innervated target tissues. Multiple growth factors including bone morphogenetic proteins, neurotrophins, glial cell line-derived neurotrophic factor family ligands and neuropoietic cytokines play instructive role at different stages of neurotransmitter development.Симпатические узлы состоят из нейрохимически и функционально различных популяций нейронов, характеризующихся специфическими проводящими путями и набором нейротрансмиттеров, включающих классические медиаторы (катехоламины и ацетилхолин), нейропептиды и малые молекулы, такие как NO, H2S, CO. Наибольшее число нейронов является норадренергическим и содержит ключевой фермент синтеза катехоламинов тирозингидроксилазу (ТГ). У млекопитающих ⅔ катехоламинергических нейронов, кроме норадреналина, используют в качестве котрансмиттера нейропептид Y. Небольшое число ганглионарных симпатических нейронов содержит фермент синтеза ацетилхолина холинацетилтрансферазу, а также нейропептиды соматостатин, вазоинтестинальный пептид (ВИП), кальцитонин-ген-родственный пептид (КГРП). Подавляющее большинство холинeргических нейронов в симпатических узлах солокализует ВИП и/или КГРП. Фенотип нейронов автономной нервной системы регулируется мишень-зависимыми и мишень-независимыми механизмами. Большинство трансмиттеров экспрессируется во время эмбриогенеза. ТГ появляется в эмбриогенезе, и доля ТГ-позитивных нейронов в онтогенезе остается постоянной. После рождения холинергические нейроны также одновременно являются норадренергическими. Экспрессия различных нейропептидов меняется во время пре- и постнатального развития. На экспрессию нейропептидов в симпатических нейронах влияют факторы роста, выделяемые тканями-мишенями. Множественные факторы роста, включая костные морфогенетические протеины, нейротрофины, нейропоэтические цитокины, могут играть инструктивную роль на различных этапах развития нейротрансмиттеров.

Calbindin 28 kDa (CB), calretinin (CR) and parvalbumin (PB) are belonged to calcium-binding proteins which are widely distributed in the nervous system and selectively expressed in certain population of neurons. These proteins are expressed not only in the central nervous system, but also in the autonomic ganglia. CB and PB are found in the sympathetic ganglia of rodents, CB and CR are found in metasympathetic intramural ganglia. Their functions are poor understood but one can suggest their important role in regulation of the Ca2+ level in the cell. Сalcium-binding proteins are also play an important role in the development of autonomic neurons. There is an increasing of the percentage of CB and CR in the metasympathetic intramural ganglia of small intestine in the early postnatal development, whereas in sympathetic ganglia the percentage of CB is decreased. Possibly, the functional meaning of such changes can be explained by the role of calcium currents in the development of neurons and the synaptic transmission.К внутриклеточным кальций-связывающим белкам, наиболее распространенным в нервной системе, селективно экспрессирующимся в определенных популяциях нейронов, относятся кальбиндин массой 28 кДа (КБ), кальретинин (КР) и парвальбумин (ПБ). Данные белки распространены не только в ЦНС, но и в узлах автономной нервной системы. В симпатических узлах у грызунов обнаруживается КБ и ПБ, в метасимпатических интрамуральных — КБ и КР. Функции их в нервной системе до сих пор не выяснены, однако можно предположить, что они играют важную роль в регуляции уровня Са2+ в клетках. Кальций-связывающие белки играют важную роль и в процессах возрастного развития автономных нейронов. В раннем постнатальном онтогенезе происходит увеличение доли КБ- и КР-иммунопозитивных нейронов в интрамуральных узлах кишки, что противоположно возрастным изменениям содержания кальций-связывающих белков в симпатических узлах, где доля КБ-позитивных нейронов снижается. Функциональное значение таких сдвигов, вероятно, связано с ролью кальциевых токов в развитии нейронов и синаптической передачи.

In the dorsal horn of the spinal cord in the plates I-IV on the thoracic and lumbar levels different subpopulations of interneurons immunoreactive for calbindin 28 kDa (CAB IR), which are specific to each plate. In the area of the medial edge of the dorsal horn, we have found a special subpopulation of CAB IR interneurons whose morphometric characteristics differ from CAB IR interneurons subpopulations of said plates. The number of CAB IR interneurons was maximal in the plate II at all levels of the spinal cord. Leveled differences are more CAB IR interneurons and larger area of the cross sections at the lumbar level.

The study was performed in 4 C57black/6 mice to examine the neurons located in T(II), L(IV), L(V) and L(VI) segments of the spinal cord (SC) ventral horn, containing 28 kD calbindin (CAB) and 200 kD neurofilament (NF) proteins. To demonstrate immunoreactive neurons, the cells were labeled with antibodies against CAB and double labeled with antibodies against CAB and NF. The total cell population was demonstrated using NeuroTrace Red Fluorescent Nissl Stain. Results have shown that CAB-immunopositive neurons were identified in ventromedial area of the ventral horn at all SC levels and were represented by Renshaw cells. CAB-positive interneurons located in the medial area of the ventral horn were present only in SC lumbar segments. CAB-positive motorneurons that were identified in the medial area of the ventral horn, were present in one SC segment (L(IV)) and were also found to contain a NF protein.

Sensory neurons represent various groups of neurons differ on their morphological, immunohistochemical and receptor characteristics. The most of large neurons with myelinated Aδ fibers contain neurofilament 200 (NF200), some small afferent neurons can bind the isolectin B4 (IB4). Also, sensory neurons may include different types of tyrosine kinases (trkA, B and C) and neurotransmitters. Neuropeptides are generally located in small and medium-sized neurons. The proportion of neurons which contain trkA decreases and the percentage of NF200-, IB4-, substance P- and CGRP-positive neurons increases during the early development. Development of different types of sensory neurons fulfill under control of neurotrophins.

Sensory neurons represent various groups of neurons differ on their morphological, immunohistochemical and receptor characteristics. The most of large neurons with myelinated Adelta fibers contain neurofilament 200 kD (NF200), some small afferent neurons can bind the isolectin B4 (IB4). Also, sensory neurons may include different types of tyrosine kinases (trkA, B and C) and neurotransmitters. Neuropeptides are generally located in small and medium-sized neurons. The proportion of neurons which contain trkA decreases and the percentage of NF200-, IB4-,substance P- and CGRP-positive neurons increases during the early development. Development of different types of sensory neurons fulfill under control of neurotrophins.

Morphological features of calcitonin gene-related peptide (CGRP)-immunoreactive neurons were studied in the sensory ganglia of the vagus and thoracic nerves in 3-, 10-, 20-, 30-, 60-, 90-, and 120-day-old rats under conditions of chemically-induced deafferentation. We found that, in rats, CGRP-containing neurons appeared in both ganglia immediately after they were born and their number decreased with aging. Most of CGRP-immunoreactive neurons were small in size, i.e., up to 600 microm2. Administration of capsaicin modified age-related changes in the number of CGRP-immunopositive neurons. In the thoracic nerve ganglion, the mean square of these cells and their number substantially decreased, whereas, in the vagus nerve ganglion, positive cells were not observed.

Morphological features of the neurons containing neurofilaments with molecular mass of 200 kD (NF200+), were studied in the sensory ganglia of thoracic and lumbar spinal nerves in rats (n = 80) during the first year of their life. Capsaicin treatment (150 mg/kg) of the newborn animals resulted in the change of age dynamics of NF200+ neurons. This was reflected by a reduction of NF200+ neuron numbers and their cross-sectional areas in both ganglia. Segmental differences included greater reduction of NF200+ neuron number in the sensory ganglion of lumbar spinal nerve in both early and late developmental periods.

Afferent neurons containing substance P (SP) were studied immunohistochemically in the sensory ganglion of the spinal nerve in 30 rats aged 10-90 days. The results obtained indicated that SP-immunoreactive neurons are present in thesel ganglia from the moment of birth. During the development, the percentage of SP-containing neurons decreased till day 10. SP-immunoreactive neurons were represented by the cells of very small or small size.

Neurons of cranial cervical, stellate and celiac sympathetic ganglia containing calbindin (CALB) were studied in rats (n = 60) aged 3-90 days using immunohistochemical method. The results obtained indicate that the largest population of CALB-immunopositive neurons was located in the stellate ganglion. The proportion of CALB-containing neurons in sympathetic para- and prevertebral ganglia decreased during the development. Final formation of CALB-immunopositive group of neurons was observed by the end of the first month of life.

Expression of vanilloid receptors in sympathetic and afferent ganglionic neurons was studied in rats of different ages (newborn, 10-day old, 20-day old, 30-day old, 60-, 180-day old) using immunohistochemical methods. The results obtained indicate that the majority of the afferent neurons in the nodose ganglion of vagus nerve (GNVN) and in the spinal ganglia (SG) were TRPV1-positive from birth onwards. The percentage of neurons containing TRPVT receptors in SG slightly increased with age up to 30 days postnatally. In the GNVN, the percentage of TRPV1-positive neurons was higher in comparison with the SG in all age groups. The vast majority of the sympathetic neurons were TRPV1-positive from birth onwards, and the percentage of TRPV1-immunoreactive neurons substantially decreased during further development. In 20-day old and older animals, we observed only few TRPV1-immunoreactive neurons in sympathetic ganglia. Finally, the percentage of neurons containing these types of neurons, become similar to adult animals to the end of the first month of life.

Morphological features of the TRPV1-immunoreactive neurons were studied in thoracic spinal nerve sensory ganglion in 10-, 20-, 30-, 60- and 90-day-old rats under normal conditions and after chemical deafferentation caused by capsaicin (100 mg/kg) subcutaneous injection at postnatal day 2. TRPV1-immunoreactive neurons differed in their morphometric characteristics: positive neurons had very small and small sizes, negative cells had the small, medium and large sizes. Capsaicin treatment of newborn rats was shown to change age dynamics of TRPV1-positive neurons resulting in the reduction of the average cell cross-sectional area and cell numbers during the whole period of observation.

Neuropeptide Y (NPY) containing 36 amino acid residues belongs to peptides widely spread in the central and peripheral nervous system. NPY and its receptors play an extremely diverse role in the nervous system, including regulation of satiety, of emotional state, of vascular tone, and of gastrointestinal secretion. In mammals, NPY has been revealed in the majority of sympathetic ganglion neurons, in a high number of neurons of parasympathetic cranial ganglia as well as of intramural ganglia of the metasympathetic nervous system. At present, six types of receptors to NPY (Y1-Y6) have been identified. All receptors to NPY belong to the family of G-bound proteins. Action of NPY on peripheral organs-targets is predominantly realized through postsynaptic receptors Y1, Y3-Y5, and presynaptic receptors of the Y2 type. NPY is present in large electron-dense vesicles and is released at high-frequency stimulation. NPY affects not only vascular tone, frequency and strength of heart contractions, motorics and secretion of the gastrointestinal tract, but also has trophic effect and produces proliferation of cells of organs-targets, specifically of vessels, myocardium, and adipose tissue. In early postnatal ontogenesis the percent of the NPY-containing neurons in ganglia of the autonomic nervous system increases. In adult organisms, this parameter decreases. This seems to be connected with the trophic NPY effect on cells-targets as well as with regulation of their functional state.

Electron microscopy was used to study the peculiarities of the development of nervous elements in the sympathetic caudal mesenteric ganglion (CMG) in the cat from the moment of birth until the end of the second month of life. The discordance in the rate of maturation of both neurons and their endings was observed. In newborn kittens, mature neurons, glial cells and synapses were observed together with many immature ones. In 14-day-old animals, the proportion of immature neurons decreased, while destruction of neurons was observed more frequently in this age. In CMG of the animals of all the age groups, axodendritic synapses were found most frequently and axosomatic synapses were observed more rarely. Finally, the ultrastructure of CMG in kittens become comparable to that of adult animals at the age of 60 days.

Background discharges of single neurons were studied from the superior cervical ganglion in newborn, 10-, 20-day-old, 1-, 2- and 6-month-old rats. In all age groups, the largest proportion of neurons exhibited aperiodic activity. The percentage of neurons with respiratory rhythmic was less. In newborn and 10-day-old rats, the frequency of discharges was low. Discharge frequency increased in 20-day-old rats. In 20-day-old and more adult rats, we found neurons bursting with cardiac frequency. The means of frequency did not statistically differ in 1-, 2- and 6-month-old rats. Thus, the pattern of neuronal activity is formed during the development in 20-day-old rats. Final maturation of this pattern is observed in 1-month-old rats.

The aim of this work was to study the anatomical characteristics of the stellate ganglion (SG) and the morphometric characteristics of its neurons in rats of different age groups (newborn, 10-, 20-, 30-, 60- and 180-day-old) using anatomical and histological methods. The results obtained indicated that in rats since birth there were three variants of branch origin from the medial margin of SG. No differences were observed in these variants between right and left SG. The sizes of both SG and its neurons increased during the first two months of postnatal development. The density of neurons in SG sections decreased from the moment of birth until the six months of age. The number of SG neurons did not change significantly in the postnatal ontogenesis. Thus, SG in rats is anatomically formed by the moment of birth, while the sizes and morphometric characteristics of SG neurons become finally stabilized by the second month of age.

Electrical activity of the cervical sympathetic trunk was studied in newborn, 10-, 20-, 30-day-old, two- and six-month-old rats and cats using the spectral analysis. The amplitude of discharges increased from the period of birth until the first moth of life in rats and until 20 days in cats. Frequencies synchronous with cardiac and respiration those were revealed in all animals. Heart-related frequencies were predominant in rats older than 20 days. Other frequencies were lower. In kittens, we did not observe any age-dependent changes of the spectrum of sympathetic nerve discharge. Discharges with high frequencies were observed in cats from the moment of birth.

The aim of this study was to determine the localization and morphometric characteristics of the stellate ganglion (SG) neurons containing muscarinic and purinoreceptors in rats of different ages (newborn, 10-, 20-, 30-, 60-, and 180-day-old) using the immunocytochemical methods. The results obtained indicated that in all the animals studied, the major part of neurons contained immunopositive P2X2, P2X6 purinoreceptors and M1 cholinoreceptors since birth onwards. A few of the neurons containing P2X3 purinoreceptors were detected in all the stages of postnatal development; these neurons were scarce in rats up to 10 days of life, after which their number increased to reach a maximal value in 20-day-old animals and then declined again. No significant changes were found in the proportion of neurons expressing M1 cholinoreceptors and P2X2, P2X6 purinoreceptors during the ontogenesis. Thus, the muscarinic synaptic transmission was already present in SG of rats by the time of their birth, while the final set of purinoreceptors on the neurons of sympathetic ganglion was formed by the age of 30 days.

Localization and the morphometric characteristics of NADPH-diaphorase--(NADPH-d)-positive neurons were studied in the superior cervical ganglion (SCG), stellate ganglion (SG) and the celiac ganglia (CG) in newborn, 10-, 20-, 30-, 60 and 180-day-old rats, mice and cats. No NADPH-d-positive neurons were found in rats and mice of all the age groups studied. In cats, the largest proportion of NADPH-d-positive neurons was found in the SG, the smaller one--in the SCG, while only the individual neurons we detected in the CG, irrespective of the animal age. In the SG, the proportion of NADPH-d-positive neurons increased during the first 20 days of life and then decreased after 30 days till the end of the second month. The content of NADPH-d-positive neurons in the CG and SCG d-remained unchanged during the development. There were no significant differences in the cross-sectional area between the neurons located in the different ganglia of animals from the same age group. It is concluded that the age development of NADPH-d-positive neurons in different sympathetic ganglia occured heterochronously was finished by the end of the second month of life.

Method based on retrograde axonal transport of horseradish peroxidase was used to study the efferent innervation of the cervical trachea in neonatal, 10-, 20-, 30-day-old and two-month-old kittens. In all the animals, labeled neurons were localized in the cranial cervical, middle cervical and cervicothoracic (stellate) sympathetic ganglia both on the right and on the left sides. Neurons were also localized at the level of medulla oblongata, in the dorsal and ambiguus nuclei of the vagus nerve. Labeled neurons were also found in the ventral horns of C(I-)C(V) spinal segments in the animals before 30 days of life. The number of sympathetic neurons, innervating the trachea, cells increased from the moment of birth, reaching a maximum by the age of 10 and 20 days and then declined up to the second month of life. The total number of parasympathetic neurons decreased gradually in the early development.

Electrical activity of the stellate ganglion was studied in newborn, 10-, 20-, 30-day-old, two- and six-month-old kittens using the spectral analysis. The development of sympathetic activity patterns was different during ontogenesis. The amplitude of discharges increased from the period of birth until the second month of kittens' life. In newborn and 10-day-old kittens, synchronous discharges of postganglionic fibers were represented by slow and low frequency impulses with frequencies of breathing and heart rate. ppears in 20-day-old kittens. The formation of the sympathetic discharge patterns ends at the second month of animals life.

Localization of the spinal cord preganglionic neurons projecting to the stellate ganglion, was studied in kittens from the moment of birth till six month of life, using the method based on retrograde axonal transport of horseradish peroxidase. The number of preganglionic neurons and spinal cord segments connected with the stellate ganglion, increased from the moment of birth till 10th postnatal day, decreasing afterwards. The proportion of preganglionic neurons in different nuclei of the spinal cord changed during the development and became comparable to that in adult animals by 6th month. The proportion of neurons in the nucleus intermediolateralis thoracolumbalis pars principalis was found to increase, while the number of neurons in the nucleus intermediolateralis thoracolumbalis pars funicularis and in the spinal cord ventral horns was decreased.

The enzyme horseradish peroxidase was administered into trachea, esophagus, heart, sternocleidomastoid muscle, and biceps of newborn, 10-, 20-day old kittens, and adult cats. The labeled neurons were located on the topical basis of the stellate ganglion. In newborn kittens, the largest cells take part in the heart innervation. In animals of other ages, the largest cells take part in innervation of the sternocleidomastoid muscle. The findings suggest that, in postnatal ontogenesis, neuronal organisation of the stellate ganglion is changing parallel to an enhancement of the neurons' size and ganglion section area.

In new-born, 10-, and 20-day-old kittens and in adult cats, the stellate ganglia branches contained both continuous and synaptically interrupted fibres. In the course of postnatal ontogenesis, the average conduction velocity of excitation and average amplitude of the responses increased. In new-born and 10-day old kittens, these are C-fibres. Apart from the latter, A delta and B fibres appeared in 20-day old kittens. In adult cats, two subgroups of all types of the fibres appeared. Since the 10-day age, synaptically interrupted responses have been recorded in anastomoses and inferior cardiac nerve following stimulation of cranial and caudal branches of the subclavian loop, the responses being conducted in both directions in adult cats.

By direct and indirect morphometry the cell density maximal diameter and area of section of neurocytes in the zones of the emergence of the basic nerves and in the centre of the stellate ganglion were determined in kittens of various ages and adult cat. There is an increase of the maximal diameter, average area of section of neurons (16.98 +/- 0.07 mm and 132.2 +/- 0.9 mm2 in newborn, 21.7 +/- 0.72 mm and 31.4 +/- 2.6 mm2 in 10-days, 6.69 +/- 0.5 mm and 355 +/- 2.4 mm2 in 20-days kitten, 4.86 +/- 0.6 mm and 634 +/- 36 mm2 in adult cat and reduction of cell density of ganglionic neurons in postnatal ontogenesis. In newborn kitten, kittens of 10- and 20-days of age and adult cat larger neurons were located in the cranial part of the ganglion. In 10 and 20 days kittens and adult cats an asymmetry between right and left stellate ganglia in the maximal diameter and average area of section of neurons was revealed. In adult cat the asymmetry in the cell density was also found between both ganglia.

Retrograde transport of horse radish peroxidase revealed the sources of forming of the initial part of the vertebral nerve in cat. The enzyme was applied on the central region of the nerve near its outlet in ganglion stellatum. Most nerve fibers the vertebral nerve contains are the processes of neurons in ganglion stellatum. Bodies of the labeled neurons in the ganglion are located in the area, attached to the site of the vertebral nerve outlet. It also contains certain number of the afferent fibers of the II-VII thoracic segments spinal ganglia. Axons of motor neurons, the bodies of which are located in ventral cornua of the spinal cord II thoracic segments may also be present. Thus, the cat vertebral nerve is mixed in the site of its forming.