Changes in neuropil ultrastructure in hippocampal field CA1 in rat pups after application of hyaluronidase.

Electron microscopy and electrophysiological studies were performed on cross-sectional slices of the hippocampus of four-week-old male rat pups (n = 35) to detect ultrastructural changes in hippocampal field CA1 and the characteristics of the formation of excitatory postsynaptic potentials in this area of the brain after incubation of slices in hyaluronidase solution (10 U/ml), whose specific substrate is the extracellular matrix glycosaminoglycan hyaluronic acid. At 1.5 min after enzyme application, there were reductions in synaptic cleft widths in axodendritic contacts of the striatum radiatum of hippocampal field CA1 by 15-25%, which were consistent with increases seen in the amplitudes of excitatory postsynaptic potentials. At 4.5 min of incubation, the lumens of synaptic clefts decreased by 45-55%: during this time there was blockade of signal transmission via Schäffer collaterals to hippocampal field CA1. Thus, the structural-functional state of glycosaminoglycans is among the factors determining the efficiency of synaptic transmission in the brain.

[Changes of the neuropil ultrastructure in the CA1 hippocampal area of rat pups after hyaluronidase treatment].

Electron microscopical and electrophysiological studies were carried out in cross-sections of the hippocampus of 4-weeks-old male rat pups (n = 35) to detect the ultrastructural changes in CA1 hippocampal area and the peculiarities of excitatory postsynaptic potential formation in this brain area after the incubation of the sections in the solution of hyaluronidase (10 U/ml), the enzyme which specifically degrades the extracellular matrix glycosaminoglycan--the hyaluronic acid. The reduction of the width of synaptic cleft by 15-25% in the axo-dendritic contacts of the stratum radiatum of CA1 hippocampal area was detected 1.5 min following the application of enzyme, coinciding with the increase of the excitatory postsynaptic potential amplitude. The width of synaptic cleft was further reduced by 45-55% after 4.5 min of incubation; during this period the blockade of signal transmission along the Schaffer's collaterals to CA1 hippocampal area was observed. Thus, the structural and functional state of glycosaminoglycans is one of the factors controlling the efficiency of synaptic transmission in the brain.

Dependence of electrical activity of neurons in rostral parts of spinal trigeminal nucleus on functional state of trigeminal Gasser ganglion.

Unilateral injection of 100 microl 1% lidocaine into the trigeminal Gasser ganglion of narcotized rats produced a long-term moderation of the discharge rate of neurons in the ipsilateral (relative to the side of injection) rostral area of the spinal trigeminal nucleus. Activity of neurons in the contralateral rostral area of the spinal trigeminal nucleus was not blocked. Functional state of neurons in the trigeminal ganglion determines discharge activity of ipsilateral neurons of the spinal trigeminal nucleus. Activity of neurons in the contralateral rostral area of spinal trigeminal nucleus was not inhibited. Functional state of the cells in the trigeminal ganglion determines the character of electrical activity of neurons in the ipsilateral rostral area of spinal trigeminal nucleus.

[Changes in the ultrastructure of the rat bulbar nuclei caused by kainic acid administration]. / Izmeneniia ul'trastruktury kletok bul'barnykh iader krysy pri vozdeistvii kainovoi kisloty.

The effect of kainic acid (KA) injection into the commissural area of nucleus tractus solitarii (NTS) of rats was studied to evaluate its influence on the ultrastructure of neurons and gliocytes at the site of injection and in the ventrolateral medulla (VM). 30 min after KA injection, in the perikarya of neurons in rostral and caudal NTS and VM the increased number of ribosomes, lysosomes, lipofuscin granules and edema of mitochondria were noted. Giant mitochondria were found in terminals and axons of myelin fibers. 14 days after KA injection, the increased volume of Golgi complex cisterns was found in single neurons in NTS rostral parts, while the neurons of caudal NTS demonstrated pronounced degenerative and destructive changes. During this period, the volume of mitochondria and of vacuoles was increased in dendrites within caudal NTS and VM, where degenerating processes of the nervous cells were found. In gliocytes of caudal NTS, the hypertrophy of cytoplasm was noted with the accumulation of dilated cisterns of endoplasmic reticulum and redistribution of nuclear chromatin. In the same areas of NTS the reaction of endotheliocytes and pericytes, perivascular edema and accumulation of microgliocytes were found. The results obtained indicate the reactive changes in VM in response to intracentral injection of neurotoxin.

[Ultrastructure of neurons and glial cells in the solitary tract nucleus and in the ventrolateral sections of the rat medulla oblongata after subdiaphragmatic vagotomy]. / Ul'trastruktura neironov i glial'nykh kletok v iadre solitarnogo trakta i v ventrolateral'nykh otdelakh prodolgovatogo mozga krys posle poddiafragmal'noi vagotomii.

Using electron microscopy, complex remodelling of neuronal and glial cell ultrastructure was demonstrated in the solitary tract nucleus and ventrolateral medulla at different time intervals following bilateral subdiaphragmatic truncal vagotomy. Four weeks after vagotomy phagocytizing microgliocytes were demonstrated in the vicinity of nuclei of degenerating neurons within the rostral, but not the caudal, areas of solitary tract nucleus and ventrolateral medulla. It is suggested that the ultrastructural changes observed in the medulla after vagotomy depend on the distribution pattern of vagal projections to the caudal brainstem.

Role of nitric oxide in modulation of afferent impulses in cutaneous branches of somatic nerves by polarized light.

Subcutaneous injection of L-NAME inhibited afferent impulse activity in n. ischiadicus and n. saphenus and abolished the increase in this activity induced by stimulation of mechanoreceptors after skin irradiation with polarized light with various spectral characteristics. Subsequent subcutaneous injection of sodium nitroprusside restored the pattern of afferent impulse activity in these nerves during repeated skin irradiation with polarized light.

[Serotonin metabolism in different areas of the brain and spinal cord in post-vibration hypotonia]. / Metabolizm serotonina v razlichnykh oblastiakh golovnogo i spinnogo mozga pri postvibratsionnoi gipotonii.

General vertical vibration enhanced the lability of the vascular tone in adult male rats. Quite often a decrease in AP occurred in rats with high initial blood arterial pressure. The data obtained suggests that the neurochemical mechanisms of post-vibration hypotony and the hypotony in control animals are different.

[Function of the hypothalamo-thyroid system after administration of kainate into the ventrolateral portion of the medulla oblongata]. / Funktsiia sistemy gipotalamus--shchitovidnaia zheleza posle vvedeniia kainata v ventrolateral'nyi otdel prodolgovatogo mozga.

Contribution of the bulbar structures to mechanisms of realization of the hypothalamo-thyroid system feedback was studied in experiments on 73 adult male Wistar rats. Histologically confirmed unilateral destruction of neurones in the caudal part of medulla oblongata ventral portions after injection of 0.65 micrograms of kainate as soon as 30 min after injection was paralleled by a trend to increase of the blood serum levels of triiodothyronine and thyroxin-binding globulin, this increase attaining reliable values by day 7 after destruction, when the effects of operation stress levelled. During the same period we observed activation of glucocorticoid-dependent choline-, serotonin-, and noradrenergic-processes in the mediobasal zone of the hypothalamus, this indicating the presence of functional relationships of medulla oblongata ventral portions with the hypothalamo thyroid system realized by disinhibition of this system during destruction of neurones in the caudal part of the ventral portion of medulla oblongata.

[Changes in gas composition of expired air during electric stimulation of the ventral medulla oblongata]. / Izmenenie gazovogo sostova vydykhaemogo vozdukha pri élektricheskoi stimuliatsii ventral'nykh otdelov prodolgovatogo mozga.

The experiments on urethane-anesthetized cats with the electrically stimulated ventral brain stem revealed that caudal ventral medulla at the depth of 1500 microns possesses structures whose electrical activation increases the level of carbon dioxide in arterial blood and in the end portion of expirate, on the one hand, and decreases the oxygen content in expirate and arterial blood, on the other hand.

[The cardiovascular effects after kainate administration into the caudal ventral sections of the medulla oblongata]. / Kardiovaskuliarnye éffekty posle vvedeniia kainata v kaudal'nuiu chast' ventral'nykh otdelov prodolgovatogo mozga.

Kainate destruction of the caudal ventral medulla's neurons raised by 70-90% the level of arterial pressure within 1 hour in anesthetised rats, the heart rate decreasing by 25-30% at the same time. Presection of the vagus at the neck level prevented the development of bradycardia and accelerated the formation of systemic arterial hypertension after administration of kainic acid to the caudal ventral medulla. The role of the vagal component in transmission of control signals from the ventral medullary structures to the heart and vessels, is discussed.

[Intracerebral connections after administration of kainate into the caudal part of ventral sections of the medulla oblongata]. / Vnutrimozgovye sviazi posle vvedeniia kainata v kaudal'nuiu chast' ventral'nykh otdelov prodolgovatogo mozga.

It was found that 1 day after unilateral destruction with kainate of neurons in the caudal ventral medulla unanesthetized animals showed disorders of arterial pressure control with a prevalence of hypertensive response. In 7 days after operation there was a decrease in the rate of neuronal uptake of serotonin and an increase in choline-, dopamine-, noradrenaline-, and glycinergic mediation in the basal hypothalamus and rostral ventral medulla, which characterize the functional state of synaptic formations in the brain stem structures connected to neurons in the caudal ventral medulla and involved in cardiovascular regulation.

[The effect of the ventral structures of the medulla oblongata on systemic arterial pressure and on the resistance and capacitance of the skeletal muscle vessels]. / Vliianie struktur ventral'nykh otdelov prodolgovatogo mozga na sistemnoe arterial'noe davlenie, soprotivlenie i emkost' sosudov skeletnykh myshts.

Following the isolation of ventral portions of the medulla oblongata from the dorsal ones and from the upper parts of the c. n. s. in cats, no changes were found in the initial level of systemic blood pressure, in perfusion pressure or in venous outflow in the m. gastrocnemius, vessels. Electrical stimulation of ventral portions of the lateral paragigantocellular nucleus under these conditions increased the systemic AP, regional vascular resistance and decreased the capacitance of the n. gastrocnemius' vessels, whereas after bilateral electrical coagulation of the nucleus the stimulation led to a stable and obvious decrease in the systemic AP and perfusion pressure in the muscle vessels. No changes of the regional vascular capacitance were noted. The significance of ventral structures of medulla oblongata in maintaining of initial AP level, formation of tonic neurogenic messages to arterial vessels of m. gastrocnemius and in actualization of the reflex neurogenic effects upon arterial and venous vessels of skeletal muscles, is discussed.

[Comparative characteristics of the changes in resistance in the vessels of the skeletal muscle and small intestine after the destruction of the structures in the ventral portions of the medulla oblongata]. / Sravnitel'naia kharakteristika izmenenii soprotivleniia v sosudakh skeletnoi myshtsy i tonkoi kishki pri razrushenii struktur ventral'nykh otdelov prodolgovatogo mozga.

Different trends and manifestation of changes of blood pressure and regional vessel resistance depending on the localization and the method (chemical or electrical) of the lesion in ventral medulla oblongata, were analyzed.

[The pressor zone in the caudal part of the ventral surface of the medulla oblongata]. / Pressornaia zona v kaudal'noi chasti ventral'noi poverkhnosti prodolgovatogo mozga.

The changes of the vessel resistance of the skeletal muscle and the small intestine perfused with constant blood flow, under electrical stimulation of the ventrolateral medulla were studied on artificially ventilated urethane-anesthetized cats. The stimulation of rostral ventrolateral medulla increased vessel resistance in both regions. The stimulation in a region 2 mm caudal the middle of the rootlets of the twelfth cranial nerves decreased the vessel resistance, but in a region 4 mm caudal the middle of the same rootlets increased the vessel resistance of the skeletal muscle and the small intestine.

[The participation of the structures of the ventral sections of the medulla oblongata in realizing vasomotor pressor reflexes]. / Uchastie struktur ventral'nykh otdelov prodolgovatogo mozga v realizatsii pressornykh vazomotornykh refleksov.

In acute experiments on cats, under constant perfusion of tibial and small intestine vessels and after bilateral electrolytic lesion of ventral portions of the paragigantocellular nucleus a decrease of initial AP by 30-35%, perfusion pressure in tibial vessels by 30% was observed whereas the changes of AP in the small intestine vessel were insignificant. The occlusion of the common carotid artery or electrical stimulation of afferent fibers of brachial plexus exerted no effect, at that. Bilateral administration of L-glutamate into ventral portions of reticular nucleus increased the perfusion pressure in tibial vessels by 15% and in those of small intestine by 35%. Carotid sinus pressor reflex induced 1.5-fold shifts of systemic AP as compared with control values.

[Effect of structures of the ventral surface of the medulla oblongata on coupled vascular functions of the small intestine]. / Vliianie struktur ventral'noi poverkhnosti prodolgovatogo mozga na sopriazhennye funktsii sosudov tonkoi kishki.

The effect of the ventrolateral medulla electrical stimulation of various intensity on resistance, capacitance and exchange functions was studied in the vascular bed of the small intestine. Brain activation with superliminal current applied to a point 2 mm rostral-wise of the middle of the twelfth cranial nerve rootlets has been shown to produce the strongest effect on the precapillary resistance of the vascular bed, whereas brain stimulation in a point 2 mm caudal-wise of this level produces a much stronger effect on the postcapillary small intestine resistance.