Neuronal pathways from low-threshold hindlimb cutaneous afferents to motoneurons innervating trunk muscles in low-spinal cats

Postsynaptic potentials (PSPs) evoked in motoneurons innervating the back and abdominal muscles in the lumbar part of the body by stimulating hindlimb cutaneous afferents were investigated in unanesthetized decerebate and spinal cats. Various types of PSP: pure excitatory postsynaptic potential (EPSP), pure inhibitory postsynaptic potential (IPSP), and mixed PSP (i.e., EPSP followed by IPSP, EPSP/IPSP; and IPSP followed by EPSP, IPSP/EPSP) were observed. The weak stimulation at 2 times threshold (2T) produced predominantly the EPSP, while at 5T the incidence of IPSP or EPSP followed by IPSP was increased. In about 20-50% of the various groups of motoneurons, PSPs evoked by ipsi- and contralateral nerves were qualitatively and quantitatively similar. For the other motoneurons, PSPs evoked by ipsi- and contralateral nerves were markedly different with respect to magnitude and/or polarity. These findings suggest that, within each motoneuron pool, some neurons act to increase stiffness of the trunk or to move vertically in response to an increased activity of cutaneous afferents, while the other motoneurons act to produce lateral bending of the trunk.     

Gegenseitige Beeinflussung von postsynaptischen Potentialen corticaler Nervenzellen nach Reizen in unspezifischen und spezifischen Kernen des Thalamus

1. The effect of non-specific excitation by medial thalamic (MT) electrical stimulation on PSP's of single nerve cells of the motor cortex elicited by electrical stimulation of specific thalamic nuclei (VL and VPL) was investigated.2. If the VL-EPSP fell on the rising phase of the MT-EPSP (stimulus intervals of 5–40 msec) the latter added to the momentary depolarization resulting in facilitation of firing. If, however, the VL-EPSP was placed on the repolarizing phase of the MT-EPSP (30–80 msec) a significant reduction in amplitude was observed. This was true for primary as well as for secondary VL-EPSP at stimulation frequencies between 0.5 and 8/sec. VL-IPSP are enhanced during the MT-EPSP, mainly during its falling phase. Here even the absolute polarization of the IPSP could be increased. MT-EPSP were strongly reduced or even suppressed during the VL-IPSP, especially during its beginning.3. The possible mechanisms of interaction within the thalamus and cortex were discussed. Although intrathalamic interaction and cortical presynaptic inhibition could not be ruled out completely, these mechanisms were considered insufficient to explain all observed phenomena. Therefore, an explanation was proposed assuming subsynaptic mechanisms in the receptive neurones themselves involving excitability changes of subsynaptic membranes.

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Mit 4 Textabbildungen

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Stipendiat der Alexander von Humboldt-Stiftung.     

Schwellenreizstromstärke und Latenzzeit einzelner Skeletmuskelzellen des Menschen in situ

Summary In 15 single sceletal muscle cells of extensor muscles of the forearm (6 healthy persons) we found a membrane potential of –83.6 (s=± 4.5) mV, a threshold current of 5.3 (s=± 0.88) · 10^–8 A and a latency of 11.9 (s=± 2.9) msec.

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Mit Unterstützung der Deutschen Forschungsgemeinschaft.

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Technische Assistenz: S. Reiher.     

Excitatory and inhibitory postsynaptic potentials in alpha-motoneurons produced during fictive locomotion by stimulation of the mesencephalic locomotor region

We tested the hypothesis that stimulation of the mesencephalic locomotor region (MLR) activates polysynaptic pathways that project to lumbar spinal motoneurons and are involved in the initiation of locomotion. Fictive locomotion was produced by MLR stimulation, and intracellular records of evoked postsynaptic potentials (PSPs) in alpha-motoneurons were computer analyzed. Stimulation of sites in the MLR that were maximally effective for the initiation of locomotion produced excitatory and inhibitory postsynaptic potentials (EPSPs and IPSPs) in all the motoneurons examined. The amplitudes of the PSPs increased as locomotion commenced. The EPSPs were largest during the depolarized phase of the step cycle, and in 17 of our 22 cells the EPSP was replaced by an IPSP of slightly longer latency during the hyperpolarized phase. The mean latency of the EPSPs measured from the stimulus artifact produced by stimulation of the MLR was 5.1 ms (3.0-7.0 ms). In all cases, the IPSP occurred 0.6 ms or more after the onset of the EPSP in the same cell. Later PSPs were sometimes observed as well. The effects of constant current injection on the membrane potential oscillations associated with fictive locomotion (locomotor drive potentials) were examined. The results showed that the amplitudes of the locomotor drive potentials (LDPs) could be affected by depolarizing and hyperpolarizing current injection. The data is consistent with the LDP having a predominant inhibitory component, which is more readily altered by current injection than is the excitatory component. The effect of constant current injections on the MLR-evoked PSPs was also examined, and it was observed that both EPSPs and IPSPs could be affected by the injected currents. The EPSPs increased in amplitude with constant hyperpolarizing current injection, and this fact rules out the possibility that the EPSP is actually a reversed IPSP. The IPSP was decreased in amplitude by hyperpolarizing current injection. Combined stimulation of the MLR and the ipsilateral high-threshold muscle or cutaneous afferents produced facilitation of both short- and long-latency MLR-evoked PSPs, suggesting that the two pathways share common interneurons. The possibility that the long-latency PSPs are produced by rapid oscillation in the locomotor central pattern generator is discussed. We concluded that MLR stimulation that evokes fictive locomotion produces both excitation and inhibition of spinal motoneurons. Spinal interneuronal systems are implicated and may be those involved in the initiation and control of locomotion. The probable relay sites for the descending pathway from the MLR to motoneurons are discussed.     

Postsynaptic potentials recorded in neurons of the cat's lateral geniculate nucleus following electrical stimulation of the optic chiasm

1. We recorded intracellularly from X and Y cells of the cat's lateral geniculate nucleus and measured the postsynaptic potentials (PSPs) evoked from electrical stimulation of the optic chiasm. We used an in vivo preparation and computer averaged the PSPs to enhance their signal-to-noise ratio. 2. The vast majority (46 of 50) of our sample of X and Y cells responded to stimulation of the optic chiasm with an excitatory postsynaptic potential (EPSP) followed by an inhibitory postsynaptic potential (IPSP); these were tentatively identified as relay cells. We quantified several parameters of these PSPs, including amplitude, latency, time to peak (i.e., rise time), and duration. 3. Among the relay cells, the latencies of both the EPSP and action potential evoked by optic chiasm stimulation were shorter in Y cells than in X cells. Furthermore, the difference between the latencies of the EPSP and action potential was shorter for Y cells than for X cells. This means that the EPSPs generated in Y cells reached threshold for generation of action potentials faster than did those in X cells. The EPSPs of Y cells also displayed larger amplitudes and faster rise times than did those in X cells, but neither of these distinctions was sufficient to explain the shorter latency difference between the EPSP and action potential for Y cells. 4. The EPSPs recorded in relay Y cells had longer durations than did those in relay X cells. Our data suggest that the subsequent IPSP actively terminates the EPSP, which, in turn, suggests that the time interval between EPSP and IPSP onsets is longer in Y cells than in X cells. Furthermore, we found that, for individual Y cells, the latency and duration of the evoked EPSP were inversely related. These observations lead to the conclusion that the latency of IPSPs activated from the optic chiasm is relatively constant among Y cells and thus independent of the EPSP latencies. Thus the excitation and inhibition produced in individual geniculate Y cells may originate from different populations of retinogeniculate axons. 5. The IPSPs recorded in geniculate relay cells following optic chiasm stimulation could be divided into three groups based on their durations. The majority of both X and Y cells showed short-duration IPSPs, whereas the remainder of Y cells displayed medium-duration IPSPs, and the remaining X cells displayed long-duration IPSPs. A positive correlation was seen between the time to peak and duration of these IPSPs.(ABSTRACT TRUNCATED AT 400 WORDS)     

Cortically evoked pre-and postsynaptic inhibition of impulse transmission to the dorsal spinocerebellar tract

Summary Synaptic actions evoked from primary afferents and the sensorimotor cortex in neurones of the dorsal spinocerebellar tract were investigated: 1. Stimulation of the anterior lobe of the cerebellum produced a small IPSP in only one but not in the other six neurones examined. 2. IPSPs were induced not only from group I fibres (in 41% of group I neurones) but also from cutaneous and/or high threshold muscle afferents (in 37%). 3. Stimulation of the contralateral sensorimotor cortex evoked IPSPs in 80% of group I neurones. The IPSP had a latency of 10–15 msec and lasted for 40–100 msec. EPSPs were evoked from the cortex in a small number of neurones. 4. Effects from the cortex were compared with those from primary afferents in individual neurones. The cortical IPSPs were induced independently of whether the neurone received monosynaptic EPSP from extensor or flexor group I fibres. The cortical IPSPs (or EPSPs) occurred more frequently in neurones which exhibited polysynaptic IPSPs (or EPSPs) from primary afferents. 5. The few FRA neurones encountered were all excited from the cortex.Excitability measurements of primary afferent terminals in or near Clarke's column showed that a terminal depolarization is evoked from the cortex in group Ib but not in Ia afferents.The relative importance of post-and presynaptic inhibition of transmission to the DSCT is discussed.     

Intracelluläre Reizung corticaler Nervenzellen

1. Intracellular records were taken from pyramidal cells of the pericruciate gyrus of anesthetized cats. Action potentials of cortical neurons do not always show an IS/SD break, but are followed regulary by a primary polarization and a delayed depolarization. The firing level is 6.0±1.6 mV (mean and S.D.).2. The time constant of cortical pyramidal cells as determined with the strengthlatency method is 8.5±2.2 msec. Almost the same value has been obtained by measuring the potential decay after break of a depolarizing and make of a hyperpolarizing rectangular pulse. Depolarizing make and hyperpolarizing break give slightly higher values.3. The mean rheobase was 2.6±1.2×10^–10 A. From the individual values for rheobase and firing level of the different cells a mean neuron resistance of 28±12×10⁶ has been calculated. This value corresponds well to the bridge unbalance after penetration of a cell membrane.4. With long depolarizing pulses adaptation of firing frequency appears during the first 70–100 msec and is followed by a steady state frequency which is linearly dependent from the current strength. Only little further drop of firing frequency can be seen during the steady state. The initial frequency decrease is accompanied by a diminution of the action potential measured from the firing level. This diminution appears eventhough the spike interval increases, and its time course is much longer than the transient change of the membrane potential. It suggests a change of firing level during adaptation possibly due to a delayed Na⁺-inactivation.5. Accommodation to linearly rising transmembranous currents is absent or negligible in cortical cells. Adaption of firing during long pulses therefore seems to be a process which appears only if the firing level is reached or surpassed.6. Some possible implications on functional aspects of the findings are discussed.

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Mit 9 Textabbildungen

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Stipendiat der Alexander von Humboldt-Stiftung.     

Langsame Rindenpotentiale bei Schmerzreizung am Menschen

Zusammenfassung Mit Hilfe elektronischer Auswerteanlagen werden reizsynchrone corticale Antworten am wachen Menschen bei Schmerzreizung extracranial abgeleitet und damit objektive elektrophysiologische Korrelate psychophysischen Untersuchungen gegenübergestellt.1. Die corticale Reizantwort bei Schmerzreizung besteht im subjektiv überschwelligen Bereich grob aus einer oberflächenpositiven Potentialschwankung mit einer reizstärkeabhängigen Dauer von 50 bis 200 msec (Amplitude 4–20 V) und einer Spitzenlatenz von 75–120 msec.2. Reizsynchrone Potentialschwankungen einer Dauer von 60 msec und einer Spitzenlatenz von 50 msec im subjektiv unterschwelligen Bereich deuten auf das Vorhandensein einer sogenannten Vorschmerzgefühlszone hin.3. Bei gleichzeitiger akustischer Reizung und Schmerzreizung dominiert, mit subjektiven Empfindungen übereinstimmend, signifikant der akustische Charakter der Komponenten des langsamen Rindenpotentials.4. Ein Vergleich psychophysisch gewonnener Intensitätsgänge bei elektrischer Schmerzreizung mit der Abhängigkeit der Amplitude der corticalen Antwortpotentiale von der Reizstärke zeigt nahezu identische Steilheit (Exponent der power function: 3,12±0,4).

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Summary Using special electronic averaging machines it is possible to measure with extracranial electrodes stimulus-locked cortical potentials following pain stimulation in human subjects. In this manner objective electrophysiological measurements may be correlated with psychophysic results.1. Above individual threshold the cortical response following pain stimulation is represented by nearly one surface-positive deflection with a duration of 50–200 msec (amplitude 4–20 V) and a latency of 75–120 msec, both increasing with the increase of stimulus strength.2. Stimulus-locked responses below individual threshold with a duration of about 60 msec and a latency of 50 msec prove the existance of the so called prepain sensation area.3. Simultaneous tone and pain stimulation results a response which shows the form of that following pure tone stimulation.4. Comparing the intensity course of equivalent psychophysic results with the dependance on stimulus strength of the amplitude of the measured slow evoked components in man there is a remarkable identity of the steepness (exponent of power function: 3,12±0,4).

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Mit 6 Textabbildungen

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Herrn Prof. Dr. Richard Wagner zum 70. Geburtstag in Verehrung gewidmet.     

Erythrocytäre G-6-PDH-Aktivität und Schilddrüsenfunktion

Zusammenfassung Bei Vorliegen einer Überfunktion der Schilddrüse ist die Aktivität der G-6-PDH der Erythrocyten der betreffenden Patienten signifikant erhöht.Der Bestimmung der Aktivität der erythrocytären G-6-PDH zur Diagnostik einer Schilddrüsenüberfunktion ist ein Platz als zusätzliches Hilfsmittel einzuräumen.

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Summary A significant increase of red cell G-6-PDH activity in cases of hyperthyreosis could be demonstrated.In cases with a normal function of the Glandula Thyreoidea the erythrocytes had an activity of 1874±481 I.U. per ml packed red cells while in severe and in moderate hyperthyreosis an increase was noted to 2465±584 resp. 2329±747 I.U. per ml packed red cells.

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Herrn Prof. Dr. med.W. Heim zum 60. Geburtstag.

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Mit Unterstützung der Deutschen Forschungsgemeinschaft.     

Supraspinal facilitation of cutaneous polysynaptic EPSPs in cat medial gastrocnemius motoneurons

Summary We examined the characteristics of postsynaptic potentials (PSPs) produced in antidromically-identified medial gastrocnemius (MG) -motoneurons by electrical stimulation of low threshold (< 3×T) distal limb cutaneous afferents in the sural (SUR) nerve in adult cats anesthetized with -chloralose, together with the effects on SUR PSPs of supraspinal conditioning stimulation of the contralateral red nucleus (RN) and pyramidal tract (PT). In the majority of MG motoneurons, SUR afferents with electrical thresholds < 1.5×T produced early excitatory synaptic potentials (EPSPs) with minimum central latency of about 2.0 ms, suggesting activation of a trisynaptic segmental pathway with two interposed interneurons. Such early EPSPs were often detectable with stimuli < 1.2×T, as determined by recording the compound action potential in the sciatic nerve and from the first appearance of the N₁ wave of the cord dorsum potential. Inhibitory synaptic potentials (IPSPs) were regularly produced by SUR volleys of only slightly greater strength (often as low as 1.3×T) and these had minimum central latencies of about 3.0 ms (about 1.0 ms longer than the earliest EPSPs), suggesting a three interneuron central pathway.Repetitive stimulation of RN and PT regularly produced facilitation of both EPSP and IPSP components in the SUR response, suggesting that these supraspinal systems directly or indirectly excite some of the same interneurons that convey the SUR effects to MG motoneurons. When using very low strength SUR stimuli, PT conditioning produced relatively pure facilitation of the SUR EPSPs but with larger SUR volleys, PT clearly facilitated both EPSPs and IPSPs. RN conditioning produced more parallel facilitation of SUR EPSPs and IPSPs. Supraspinal control of the polysynaptic pathway producing SUR EPSPs is of particular interest because of earlier evidence that this pathway is differentially distributed to motoneurons of fast twitch versus slow twitch MG motor units.Supported by USPHS Postdoctoral Fellowship 1F32NS 06131Supported by Muscular Dystrophy Society of America Post-doctoral FellowshipSupported by USPHS Postdoctoral Fellowship 1F32NS 05677     

Das Verhalten des filtrierten Plasmaanteils bei einseitig Nephrektomierten

Zusammenfassung Bestimmungen der Inulin- und PAH-Clearance ergaben bei elf normotonen einnierigen Patienten eine im Vergleich zum effektiven Nierenplasmastrom stärkere Einschränkung des Glomerulumfiltrates mit daraus resultierender Erniedrigung der Filtrationsfraktion auf 14,4±3,46%. 14 weitere hypertone einnierige Patienten zeigten demgegenüber eine statistisch signifikant höhere Filtrationsfraktion von 19,1±3,1% (t=3,86,p<0,005).

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Summary Filtration Fraction in Patients with Solitary Kidney. In 24 patients with a solitary kidney (21 unilateral nephrectomized and 3 with congenital unilateral renal aplasia) Inulin- and PAH-Clearances were studied. Results indicate a statisticaly significant decrease of filtration fraction in 11 normotensive patients as compared to 14 hypertensive patients. (F. F. 14.4±3.46, 19.1±3.1, respectively,t=3.86,p<0.005).

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Herrn Prof. Dr.E. Wollheim zum 65. Geburtstag.

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Technische Assistentin Frl.G. Hartwig.     

Posttetanic and frequency potentiation in slices of rat olfactory cortex

The electrical tetanization of the lateral olfactory tract at a frequency of 30/sec for 15 sec elicited the development of posttetanic potentiation of populational EPSP and IPSP in surviving slices of rat olfactory cortex. The stimulation of the lateral olfactory tract by series of stimuli at a constant frequency of 10/sec and with intervals of 4–5 sec between series facilitates the emergence of the phenomenon of frequency potentiation. The data obtained indicate that such forms of functional plasticity as posttetanic and frequency potentiation are manifested in the pyriform cortex.Translated from Fiziologicheskii Zhurnal SSSR imeni I. M. Sechenova, Vol. 76, No. 4, pp. 425–429, April, 1990.     

Einfluß einer Adrenalektomie auf das Membranpotential einzelner Skeletmuskelzellen

Zusammenfassung Bei insgesamt 371 Einzelzellen des isolierten Zwerchfells von 7 adrenalektomierten Ratten zeigte das Membranpotential mit –84,4 (s=± 6,3) mV gegenüber einem Kontrollwert von –85,1 (s=± 6,5) mV bei insgesamt 347 Zellen von 6 Tieren keinen statistisch signifikanten Unterschied. Die Bedeutung des Befundes besteht darin, daß die gemessenen Membranpotentialwerte (E _m ) den nach der Gleichung vonHodgkin undHorowicz berechneten (E _{K + Na}) entsprechen, die sich aus den gemessenen intra-extracellulären Natrium- und Kaliumkonzentrationen ergeben. — Damit weisen die Befunde darauf hin, daß die in vivo gemessene Erniedrigung des Membranpotentials (Depolarisation) an einzelnen Muskelzellen adrenalektomierter Tiere als Folge einer erhöhten Kaliumkonzentration zu verstehen ist, — d.h. die Depolarisation in vivo würde bei Entzug der Nebennierenhormone lediglich durch die veränderten Umgebungsbedingungen und nicht durch Änderungen der Membraneigenschaften herbeigeführt.

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Summary Single muscle cells of the isolated diaphragm of adrenalectomized and control rats were punctured with microelectrodes, and the membrane resting potentials were measured. In 371 cells of 7 adrenalectomized animals we found a mean resting potential of –84.4 (s=± 6.3) mV; in 347 cells of 5 control animals we found a mean resting potential of –85.1 (s=± 6.5) mV. — I. e. there is no significant difference in the resting potentials between adrenalectomized and control rats. The measured potentials (E _m ) agree with the values calculated by the equation ofHodgkin andHorowicz (E _{K + Na}). The calculation bases upon measured intra- and extracellular concentrations of sodium and potassium. These findings suggest that the in vivo decreased resting potentials in adrenalectomized rats are due to the increased extracellular potassium concentration. There are no indications to a change of the total conductivity of the cell membrane for ions.

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Mit Unterstützung der Deutschen Forschungsgemeinschaft.

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Technische Assistenz:S. Winterling.     

Recurrent inhibition from motor axon collaterals of transmission in the Ia inhibitory pathway to motoneurones

1. The effects of impulses in recurrent motor axon collaterals on reflex transmission from different types of primary afferents to motoneurones were investigated in the cat by conditioning of PSPs evoked in motoneurones.

2. IPSPs evoked by volleys in large muscle spindle (Ia) afferents were effectively decreased when preceded by an antidromic stimulation of ventral roots. Some IPSPs from group II muscle afferents and low threshold cutaneous afferents were also slightly depressed, while other PSPs were unaffected.

3. The depression of the IPSPs could be evoked by antidromic volleys, which produced neither conductance changes in the motoneurones nor depolarization of Ia afferent terminals.

4. The effect on the Ia IPSPs is most likely due to post-synaptic inhibition of the Ia inhibitory interneurones, evoked through α-motor axon collaterals and Renshaw cells. The depression of some IPSPs from flexor reflex afferents is explained by a convergence of excitatory effects from these afferents on the Ia inhibitory interneurones.

5. The results indicate a selective recurrent control from motor axon collaterals of the interneurones in the reciprocal Ia inhibitory pathway to motoneurones.

     

In vivo recording of postsynaptic potentials and low threshold spikes in W cells of the cat's lateral geniculate nucleus

Summary We obtained good intracellular recording from 5 W cells in the C-laminae of the cat's lateral geniculate nucleus. The recordings were made from an anesthetized and paralyzed in vivo preparation. We found a consistent pattern for the postsynaptic potentials evoked from activation of the optic chiasm: first was an IPSP followed by an EPSP. This is very different from the pattern seen in X and Y cells, for which an EPSP always appears first and is then followed by an IPSP. We interpret the pattern for W cells as follows. The initial IPSP is disynaptic; this involves retinogeniculate conduction over very fast Y axons and a relay through an interneuron. The EPSP is monosynaptic, reflecting retinogeniculate conduction over very slow W axons. A possible implication for this is that activity over the Y pathway may generally inhibit geniculate W cells before these W cells can be excited by their retinal afferents. Finally, we elicited from each of these W cells voltage-dependent, low threshold spikes, which are very similar to those displayed by X and Y cells. These spikes can interrupt normal retinogeniculate transmission, and they are prevented by maintaining relatively depolarized membrane potentials.     

Messung von Änderungen des Membranwiderstandes markhaltiger Nervenfasern mit der „Saccharose-Trennwand“-Methode

Summary The sucrose-gap method of Stämpfli (1954) has been modified by the arrangement of two sucrose-gaps on both sides of a segment of a bundle of myelinated nerve fibres. This new method is convenient not only for measuring changes of membrane potential but also for examination of membrane resistance and action potential. On the average, 80% of the true changes of membrane potential can be recorded. The action potentials are strictly monophasic, their amplitude being about 80 mV, their duration 1–2 msec. Changes in membrane resistance are determined by recording current-voltage curves under various experimental conditions.

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Mit 3 Textabbildungen

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Mit Unterstützung durch die Deutsche Forschungsgemeinschaft.     

Short latency activation of pyramidal tract cells by Group I afferent volleys in the cat

1. The contralateral bulbar pyramids were explored with low impedance micro-electrodes in cats anaesthetized with chloralose to reveal the effect of Group I afferent volleys (deep radial nerve of the forelimb) on pyramidal tract (Pt) cells.

2. Low rate (0·5/sec) stimulation of Group I afferents produced small responses (5-30 μV) in the bulbar pyramid which could be detected only with response averaging methods. The responses appeared with an initial latency of 7·0-11·2 msec and reached peak amplitude in 15·7 msec (mean latency). The pyramidal tract origin of the potential was demonstrated by its depression at stimulus rates above 1-2 sec and its disappearance at rates above 4/sec.

3. Recordings of neurones in the Group I cortical projection zone of the posterior sigmoid gyrus revealed that several types of cells, including Pt cells, were activated by Group I afferent volleys.

4. Pt cells responding to Group I afferent volleys frequently received convergent actions from low threshold cutaneous nerve volleys.

5. Averaged response recordings from electrodes positioned in the medial portions of the lateral funiculus of the spinal cord at the level of C₂, revealed a response to Group I afferent volleys as early as 7·4 msec which possessed the same characteristics as the relayed response to Group I in the bulbar pyramids. Some Pt cells, activated by Group I volleys orthodromically, could also be antidromically activated by stimulation of the recording site in C₂.

6. It was concluded that group I afferent volleys can influence, after short latencies, Pt and non-Pt cells and that some of these Pt cells gave rise to axons incorporated in the corticospinal tract.

     

Die Schwellenreizstromst?rke einzelner Skeletmuskelzellen des Menschen bei der Niereninsuffizienz

Zusammenfassung Mit Hilfe von Ling-Gerard-Mikroelektroden wurde unter Verwendung einer Brückenschaltung an einzelnen Skeletmuskelzellen von fünf niereninsuffizienten Patienten eine deutliche Erhöhung der Schwellenreizstromstärke um 2,40 × 10^–8 Amp gegenüber der Norm (sechs klinisch gesunde Personen) gemessen, d. h. von 4,35 (s=±2,13) × 10^–8 Amp auf 6,73 (s=±2,50)·10^–8 Amp (P<0,001). Die Befunde sind als Folge eines erniedrigten Membranwiderstandes unter den Bedingungen der Niereninsuffizienz zu verstehen.

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Summary Using Ling-Gerard-microelectrodes in connection with a special bridge circuit the rheobase was determined in single cells of sceletal muscle in situ of 5 patients with renal insufficiency. The rheobase (r) in these patients was 6.73 (s=±2.50)·10^–8 Amp as compared to 4.35(s=±2.13)·10^–8 Amp in 6 normal individuals ( ^r =+2.40·10^–8 Amp;P<0.001). These findings can be explained as a consequence of a decreased membrane resistance caused by the conditions of renal insufficiency.

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Herrn Professor Dr.H. Schwiegk zu seinem 60. Geburtstag gewidmet.

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Mit Unterstützung der Deutschen Forschungsgemeinschaft.     

Cervical effects on abducens motoneurons and their interaction with vestibulo-ocular reflex

Summary The effect of neck afferents on abducens motoneurons and their interaction with the vestibulo-abducens reflex were examined in chloraloseanesthetized or unanesthetized, decerebrate cats. The test reflex elicited in the abducens nerve by stimulation of the contralateral vestibular nerve was inhibited by contralateral and facilitated by ipsilateral cervical dorsal root or neck joint stimulation. These reciprocal effects were obtained by stimulation at the level of C2 and C3, but not from C5 or lower. Contralateral and ipsilateral cervical stimulation induced IPSPs and EPSPs, respectively, in abducens motoneurons. The latencies were 2.8–6.0 msec for the IPSP and 2.8–5.3 msec for the EPSP after stimulation of the dorsal root.The labyrinthine-induced disynaptic IPSP or EPSP was facilitated by conditioning stimulation of the contralateral and ipsilateral cervical dorsal root, respectively. It is thus postulated that the cervico-abducens and vestibuloabducens reflex pathways converge upon common inhibitory or excitatory interneurons in the vestibular nuclie. Labyrinthine- and cervical-induced responses of the presumed interneurons in the vestibular nuclei or those of their axons recorded in the abducens nuclie were consistent with the above view.Lesion experiments in the brain stem indicated that afferent volleys from the neck joint ascend ipsilaterally in the spinal cord, cross to the contralateral side in the brain stem, and eventually project to the vestibular nuclei, thus interacting with the vestibulo-ocular reflex activity.A possible functional role of the cervical effects on the ocular motoneuron was briefly discussed.     

Physikalische Eigenschaften des Australia-SH-Antigens (Au-SH-Antigen)

Zusammenfassung Die Komplementbindungsreaktion weist ein Au-SH-Partikel nach, das sich weder in Dichte, Sedimentation, chromatographischem Verhalten, noch in seiner Morphologie von dem Partikel unterscheidet, das im Immundiffusionstest bestimmt wird. Zwischen beiden serologischen Tests besteht außerdem eine sehr gute Korrelation der Antigentiter. Die Sedimentationskonstante des Au-SH-Antigens beträgt 40 ±7 S, seine Dichte 1.16 g/cm³. Aus beiden physikalischen Konstanten berechnet sich ein mittlerer Durchmesser von 21.2 ±2 m. Dieser Wert entspricht der elektronenoptisch ermittelten Größe des Au-SH-Antigens. Beide Bestimmungsmethoden liefern eine Größenvariation, die sich von 14 bis 27 m erstreckt.

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Physical properties of Australia-SH-antigen

Summary The complement fixation test detects an Australia-SH-antigen particle which physically (density, sedimentation, chromatographic behaviour on DEAE-cellulose) and morphologically is identical to that particle which is detected by immunodiffusion. Between both serological tests there is an excellent correlation of antigen titers. The sedimentation coefficient of Australia-SH-antigen is 40 ±7S, its density in sucrose 1.16 g/cm³. From these both physical constants the average diameter of Australia-SH-antigen can be calculated to 21.2 ±2 m, a value which corresponds to the seize of Australia-SH-antigen estimated by electron microscopy. The seize of the particles varies between 14 and 27 m.

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Prof. Dr. med. R.Haas zum 60. Geburtstag.

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Die Untersuchungen wurden von der Deutschen Forschungsgemeinschaft unterstützt.