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Biomedical subjects

H Seller

Publications and source records attributed to H Seller.

At least 55 records · Page 3Linked to original sources
PubMed1987

Rostrocaudal location of sympathetic preganglionic neurones within the third thoracic segment of the cat spinal cord investigated by the retrograde transport of horseradish peroxidase and by recording of antidromic field potentials.

The rostrocaudal location of sympathetic preganglionic neurones (SPNs) in the intermediolateral cell column of the third thoracic segment was studied in the cat by the retrograde transport of horseradish peroxidase and by recording of antidromic field potentials in the spinal cord in response to stimulation of white ramus T3. By both methods, the position of the rostral and caudal border of SPNs was determined in relation to the entry of segmental dorsal roots. It was found that SPN's are confined in the spinal cord to the length of one segment (9494 +/- 823 micron), but are shifted rostrally by about 3 mm with respect to the point of entry of the dorsal roots of segment T3.

Animals↗
PubMed1987

Afferent connections and spinal projections of the pressor region in the rostral ventrolateral medulla of the cat.

Following microinjection of wheat germ agglutinin conjugated to horseradish peroxidase (WGA-HRP) into the pressor region of the rostral ventrolateral medulla of the cat, the medulla, pons and hypothalamus were examined for retrogradely labelled cell bodies, while the thoracolumbar segments of the spinal cord were examined for anterogradely labelled axons. Dense groups of labelled cells were found in the following areas: (1) the nucleus of the solitary tract, particularly the medial, ventrolateral and commissural subnuclei; (2) the ambiguous complex and immediately surrounding area; (3) the Kölliker-Fuse nucleus in the pons; (4) the paraventricular nucleus and lateral hypothalamic area. In the spinal cord, labelled axons formed a band extending throughout the dorsolateral and ventrolateral funiculi at thoracic segments, while terminal labelling was observed in the intermediolateral nucleus and to a lesser extent the central autonomic area, but not in other parts of the grey matter. The findings are discussed in relation to the role of the rostral ventrolateral medulla in cardiovascular regulation, particularly the baroreceptor reflex.

Afferent Pathways↗
PubMed1987

The influence of cardiopulmonary receptors on long-term blood pressure control and plasma renin activity in conscious dogs.

The isolated and combined influence of cardiopulmonary and arterial baroreceptor denervation on long-term blood pressure (MAP), heart rate (HR), plasma volume (PV) and plasma renin activity (PRA) was studied in 10 conscious, chronically instrumented foxhounds receiving a normal sodium diet. Cardiopulmonary denervation was achieved by surgically stripping both thoracic vagi. Near complete arterial baroreceptor denervation, leaving most cardiopulmonary fibres intact, was made by left vagal deafferentiation which has been shown to eliminate most aortic baroreceptor afferents, and a carotid sinus denervation. Five groups were studied: (I) control (n = 9), (II) cardiopulmonary denervation (n = 5), (III) aortic baroreceptor denervation (n = 5), (IV) arterial baroreceptor denervation (n = 4) and (V) total denervation (n = 6). No changes in PV were observed. Only group V revealed significantly higher levels of MAP (119.5 +/- 5.4 vs. 100.1 +/- 1.6 mmHg; P less than 0.05), HR (118.1 +/- 4.4 vs. 87.8 +/- 3.7 beats min-1; P less than 0.001) and PRA (3.0 +/- 0.8 vs. 0.9 +/- 0.2 ng AI m-1 h-1; P less than 0.05). It is suggested that the isolated function of either cardiopulmonary or arterial baroreceptors is sufficient to maintain these variables at a normal level. Contrary to the results of other reports the cardiopulmonary receptors do not seem to regulate MAP at a level about which the arterial baroreceptors operate. When both groups of afferents were interrupted MAP, HR and PRA rose to significantly higher levels, implying that cardiopulmonary and arterial baroreceptor afferents interact in a sense of a non-additive attenuation.

Animals↗
PubMed1986

Three types of sympathetic preganglionic neurones with different electrophysiological properties are identified by intracellular recordings in the cat.

Intracellular recordings were obtained from sympathetic preganglionic neurones (SPN) of the third thoracic segment in cats. Based on differences in their active and passive electrophysiological properties, three different types of SPNs were discerned: Type A neurones had a high resting membrane potential (RMP) (-60 to -86 mV) and a low input resistance (RN) 12-23 M omega). Action potentials of these neurones had a pronounced IS-SD inflexion and a prominent shoulder in their falling phase. Spikes were rarely generated from the on-going synaptic activity. Type B neurones had a lower RMP (-48 to -65 mV) and a higher RN (21-37 M omega). Their action potentials were characterized by an after-depolarization; they showed a slight IS-SD inflexion and a less pronounced shoulder in their falling phase. The after-depolarization was abolished by membrane hyperpolarization in a time dependent way. A hyperpolarization of at least 50 ms duration was required for its abolition. The after-depolarization was also abolished during repetitive discharges. In most of these neurones spikes were generated at irregular intervals and low rates (0.06-4.6 spikes/s) from the synaptic activity. Type C neurones were similar to type B neurones, but their action potentials did not show the after-depolarization. Additionally, spikes were generated at fairly regular intervals and rather high rates (0.8-6.5 spikes/s). The rate of spike repolarization of all neurones was markedly increased by hyperpolarization and decreased by membrane depolarization. Current-voltage curves of some type B and C neurones showed a marked rectification upon membrane hyperpolarization.(ABSTRACT TRUNCATED AT 250 WORDS)

Action Potentials↗
PubMed1985

Morphology of sympathetic preganglionic neurons in the thoracic spinal cord of the cat: an intracellular horseradish peroxidase study.

Horseradish peroxidase was intracellularly injected into sympathetic preganglionic neurons (SPN) of the third thoracic segment in cats. Seven neurons were reconstructed from serial horizontal or parasagittal sections of the spinal cord. The cell bodies of all neurons were located in the n. intermediolateralis pars principalis (ILp). They were spindle-shaped with the long axis in craniocaudal direction or large and multipolar or small and oval in shape. Preferentially on the cranial and caudal pole of the cell body, five to eight primary dendrites arose from the cell body. Dendritic branches were traced to their terminations at distances up to 1,330 microns from the cell body. The dendritic fields of all SPNs were strictly oriented in the longitudinal direction with a total length of 1,500-2,540 microns. The cranial and caudal dendritic fields were about equal in length but, with one exception, the degree of branching was always greater in the cranial than in the caudal dendritic field. The dendritic fields of all SPNs were primarily restricted to the ILp. In the mediolateral direction it extended from 130 to 360 microns and in the dorsoventral direction from 50 to 180 microns. Only rarely, a higher-order dendrite left the boundaries of the ILp and projected dorsolaterally or laterally into the white matter or ventromedially or medially into the adjacent n. intercalatus. All dendrites showed various forms of spines. At a distance of 132-437 microns from the cell body the axon arose as a direct extension of a process which closely resembled a primary or second-order dendrite. The axons projected ventrally and mostly caudally along the lateral border of the gray matter until they turned laterally at the end of the ventral horn. No axon collaterals were observed.

Adrenergic Fibers↗
PubMed1985

Segmental distribution of afferent fibres in the left inferior cardiac nerve of the cat studied by anterograde transport of horseradish peroxidase.

The segmental projection of afferent fibres in the left inferior cardiac nerve of the cat was studied by using the anterograde transport of horseradish peroxidase (HRP). HRP-positive cell bodies were detected in ipsilateral dorsal root ganglia from segments T1 to T7. No labelled neurones were found at segments C8 and T8. The total number of labelled neurones ranged from 157 to 535 neurones in individual experiments. The majority of neurones (70-88%) were localized in the dorsal root ganglia of segments T2-T4. Labelled neurones were oval shaped, and most neurones had a long axis in the range from 20 to 40 microns.

Afferent Pathways↗
PubMed1985

An intracellular study of the synaptic input to sympathetic preganglionic neurones of the third thoracic segment of the cat.

In chloralose anaesthetized, paralyzed and artificially ventilated cats intracellular recordings were obtained from sympathetic preganglionic neurones (SPN) of the third thoracic segment of the spinal cord identified by antidromic stimulation of the white ramus T3. The synaptic input to SPNs was assessed, in cats with intact neuraxis or spinalized at C3, by electrical stimulation of segmental afferent fibres in intercostal nerves and white rami of adjacent thoracic segments and by stimulation of the ipsi- and contralateral dorsolateral funiculus and of the dorsal root entry zone of the cervical spinal cord. In both preparations SPNs showed on-going synaptic activity which predominantly consisted of excitatory post-synaptic potentials (EPSPs). Inhibitory post-synaptic potentials (IPSPs) were rarely observed. EPSPs were single step (5 mV) or, less frequently, large (up to 20 mV) summation EPSPs. The proportion of SPNs showing very low levels of on-going activity was markedly higher in spinal than in intact cats. Stimulation of somatic and sympathetic afferent fibres evoked early EPSPs (amplitude 3 mV, latency 5-22.3 ms), and late, summation EPSPs (amplitude up to 20 mV, latency 27-55 ms). Early and late EPSPs were evoked in nearly all SPNs in which this synaptic input was tested in the intact preparation (from 79-93% of the SPNs). In spinal cats, early EPSPs were evoked in 88% of the SPNs, whereas late EPSPs were recorded only in half of the neurones. No evidence for a monosynaptic pathway from these segmental afferent fibres to SPNs was obtained. In both intact and spinal cats, stimulation of the dorsolateral funiculus evoked early and late EPSPs in SPNs. Late EPSPs were recorded in 70% and 37% of the SPNs in intact and spinal cats, respectively. Early EPSPs, however, were evoked in all neurones. The early EPSPs evoked by stimulation of the dorsolateral funiculus had several components which are suggested to arise from stimulation of descending excitatory pathways with different conduction velocities. The following conduction velocities were calculated in intact (spinal) cats: 9.5-25 m/s (7.8-13.2 m/s), 5.7-9.5 m/s (5.5-7.8 m/s), 3.8-5.7 m/s (3.2-5.5 m/s), and 2.6-3.8 m/s (2.1-3.2 m/s). EPSPs of these various groups were elicited in a varying percentage in SPNs. EPSPs of the most rapidly conducting pathway were subthreshold for the generation of action potentials; some EPSPs of this group had a constant latency suggesting a monosynaptic pathway to SPNs. Stimulation of the dorsal root entry zone at the cervical level yielded essentially the same results as stimulation of the dorsolateral funiculus.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1985

Respiratory modulation of sympathetic activity.

Sympathetic activity recorded from cardiac and renal nerves was correlated with phrenic and internal intercostal nerve activity under normocapnea and hypercapnea. Cats were anesthetized with halothane for surgery switching to chloralose for recording. Both vagal and carotid sinus nerves were cut, animals were paralyzed and artificially ventilated. We found that sympathetic activity followed the rhythmic pattern of phrenic nerve discharge fairly closely except in two important respects: first, sympathetic activity was significantly depressed during early inspiration and second, it reached a minimum during post inspiration while phrenic activity was decaying but still active. These effects were accentuated when PACO2 was raised. In one cat early inspiratory depression was the only manifestation of respiratory modulation of sympathetic activity superimposed on an otherwise tonic pattern. In 4 cats sympathetic activity increased in an augmenting fashion in parallel with the augmenting discharge of expiratory alpha motoneurones. We suggest that respiratory-related, excitatory and inhibitory inputs modulate sympathetic activity at the brainstem level. Inspiratory and possibly expiratory interneurones may be the source of activation, and inhibitory inputs may derive from early inspiratory and postinspiratory interneurones. The inhibitory effects may be the only manifestation of respiratory modulation during strong tonic drive of the sympathetic activity.

Animals↗
PubMed1982

Antidromic activation of sensory afferent fibres in sympathetic nerves of the cat by stimulation of collaterals within the dorsal medulla oblongata.

Action potentials were evoked in the white ramus of the third thoracic segment by electrical stimulation in the dorsal medulla oblongata. The following findings indicate that these potentials are due to antidromic activation of collaterals of afferent fibres in sympathetic nerves rather than to orthodromic synaptic activation of preganglionic sympathetic neurones via bulbospinal sympatho-excitatory pathways: (i) they had short latencies yielding intraspinal conduction velocities of 13-43 m/sec; (ii) they followed short trains of stimuli at frequencies up to 600 Hz; and (iii) they were abolished by cutting the dorsal roots of the same spinal segment.

Afferent Pathways↗
PubMed1981

Early and late contributions to our knowledge of the autonomic nervous system and its control made by German scientists.

A summary is given of the German contribution to the development of our knowledge of the autonomic system. Although no major contributions were made in the early centuries and even during and immediately following the Renaissance and the Reformation (1517), there ultimately was a development of strength in the physiological sciences during the eighteenth and nineteenth centuries which remained dominant even during the early decades of the twentieth century. Discovery of the inhibitory action of the vagus nerves by the Weber brothers in 1845 and the description of the depressor reflex and the principle of "feedback" by Cyon and Ludwig in 1866 are examples of high attainment in the study of autonomic nervous system physiology. Many of the other discoveries and subsequent development which occurred in Germany are described. The present symposium has demonstrated the present high attainment in this field.

Animals↗
PubMed1981

Tonic catecholaminergic inhibition of the spinal somato-sympathetic reflexes originating in the ventrolateral medulla oblongata.

In chloralose-anesthetized cats activity of the spinal and supraspinal components of the somato-sympathetic reflex were evoked in the white ramus at T3 by stimulation of the corresponding intercostal nerve. A blockade of all spinal pathways by means of a reversible cold blockade of the spinal cord at C2-C3 produced the following effects: (1) mean arterial blood pressure fell to 30-50 mm Hg and the tonic background activity in the white ramus was markedly reduced; (2) the amplitude of the spinal reflex was significantly increased and the supraspinal reflex was completely abolished; (3) localized cold block of the dorsolateral funiculus produced the same effect as cold block of the whole spinal cord; (4) neither baroreceptor denervation nor midcollicular decerebration altered these effects; and (5) the alpha-adrenoceptor agonist clonidine reduced the increased amplitude of the spinal reflex during cold blockade; this effect was reversed by the alpha-adrenoceptor antagonist yohimbine. Bilateral cold blockade of areas on the ventrolateral surface of the brain stem between the rootlets of the hypoglossal nerve and the trapezoid body caused the same effect on background and reflex activity in the white ramus as did spinal cord blockade. A mapping of the catecholaminergic (CA) neurons in the lower brain stem of the cat by means of the fluorescence method showed CA neurons in the ventrolateral medulla at two levels: (1) one group of neurons in the caudal medulla, which lies ventral and dorsal to the lateral reticular nucleus (corresponding to area A1 in the rat); and (2) a second group found more cranially and located ventrally to the facial nucleus (corresponding to area A5 in the rat). CA nerve terminals in the spinal cord mainly innervate the intermediolateral cell column. From these findings it is concluded that in the anesthetized cat the spinal component of the somato-sympathetic reflex is modulated by a descending tonic inhibition. This inhibition is independent of baroreceptor input. The pathways descend in the dorsolateral funiculus of the spinal cord, and it is suggested that they originate either in the cranial part of area A1 and/or area A5.

Animals↗
PubMed1980

Tonic descending inhibition of the spinal somato-sympathetic reflex from the lower brain stem.

In chloralose-anaesthetized cats the spinal and supraspinal components of the somato-sympathetic reflex were evoked in the white ramus at T3 and/or L2 by stimulation of intercostal and spinal nerves. A reversible blockade of all ascending and descending spinal pathways was performed by cooling the spinal cord between the second and third cervical segment. Total blockade of conduction was produced at temperatures below 8.5 degrees C (281.5 K). The spinal blockade produced the following reversible effects. (1) Mean arterial pressure fell to 30-50 mm Hg (4.0-6.7 kpa) and the tonic background activity in the white ramus was reduced to 0-24% of control (mean 12.1 +/- 10.0%). (2) The amplitude of the early spinal reflex was increased from 100% to 111-316% (mean 200.9 +/- 49.5%, n = 49) at the thoracic level and to 125-342% (mean 181.4 +/- 74.4%, n = 7) at the lumbar level. The onset latency of the spinal reflex at T3 (range 8-21 msec) was shortened by 0.5-3.0 msec (mean 1.7 +/- 0.9 msec). (3) Supraspinal components were completely abolished. (4) Neither baroreceptor denervation nor midcollicular decerebration altered these effects. (5) The cold block induced increase of the amplitude of the spinal reflex was reduced by the alpha-adrenoceptor agonist clonidine; this effect was reversed by the alpha-adrenoceptor antagonist yohimbine. Selective cooling of the dorsolateral funiculus caused the same effects on the spinal and supraspinal reflexes as cold block of the whole spinal cord. From these findings it is concluded that in the anaesthetized cat the spinal component of the somato-sympathetic reflex is modulated by a descending tonic inhibition. This inhibition acts at both the thoracic and the lumbar level and its origin is in the medulla oblongata. This inhibition is, however, independent of baroreceptor inputs. The pathways descends in the dorsolateral funiculus. It is suggested that noradrenaline or adrenaline might be involved in the transmission of this inhibitory influence.

Adrenergic Fibers↗
PubMed1979

Bulbospinal projections to the intermediolateral cell column: a neuroanatomical study.

The location of those neurones in the brain stem that project to the intermediolateral column (ILC) from which preganglionic sympathetic neurones have their origin was studied by the method of retrograde transport of horseradish peroxidase (HRP). In cats 30--50 nl of a 30% HRP solution was injected into the region of the ILC at T3 or L1 on one side. After a survival period of 72 h the lower brain stem from C1 to the inferior colliculi was sectioned and prepared for histological study under brightfield illumination. Neurones stained with exogenous HRP were found in three regions: (a) in the ipsilateral, dorsomedial part of the nucleus of the solitary tract (NTS) (43% of all labeled neurones), in the cranial part of the NTS, and also on the contralateral side (7%); (b) in the ventrolateral reticular formation beginning at the level of the obex up to 8 mm cranial to the obex (25% ipsilateral, 3% contralateral); and (c) in the ventral part of the raphe nuclei (postpyramidal and inferior central nucleus) from 2 to 9 mm cranial to the obex (22%).

Animals↗
PubMed1976

Reduction of renal nerve activity by volume expansion in conscious cats.

In conscious cats with intact or denervated baroreceptors volume expansion of 5-15% of blood volume was performed with dextran and isotonic sodium chloride. Renal sympathetic activity (RSA), electroencephalogram (EEG) blood pressure (BP) and heart rate (HR) were recorded. RSA was reduced by 25-85% in 10 experiments out of 11 by volume expansion both with dextran and isotonic sodium chloride. Reduction of RSA could not be related to different states of wakefulness as indicated by the EEG, so could only be caused by volume expansion, although no quantitative correlation could be detected. No differences were observed between animals with intact and denervated baroreceptor. In most experiments BP and HR decreased during volume expansion up to -25 mmHg and up to -23 beats/min, respectively. The degree of BP and HR reduction could not be related to the degree of RSA reduction. The results suggest that changes in RSA might be involved in the renal response to volume expansion.

Animals↗