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E Jankowska

Publications and source records attributed to E Jankowska.

At least 55 records · Page 3Linked to original sources
PubMed1998

Modulation of responses of feline gamma-motoneurones by noradrenaline, tizanidine and clonidine.

1. Effects of noradrenaline (NA) and the alpha2 agonists tizanidine and clonidine were tested on extracellularly recorded responses of gamma-motoneurones in deeply anaesthetized cats. Two types of responses were used; firstly, short latency phasic responses evoked by electrical stimulation of group II afferents in a muscle nerve and, secondly, tonic background discharges. 2. Responses evoked by group II muscle afferents were depressed when NA and tizanidine were applied ionophoretically close to a gamma-motoneurone and when clonidine was applied systemically. The number of spike potentials evoked by stimulation of these afferents decreased and their latencies increased. Responses evoked by flexor or extensor afferents in gamma-motoneurones innervating flexors or extensors were similarly depressed. 3. Tonic discharges were inconsistently and/or insignificantly affected by locally applied NA and tizanidine but were depressed by systemically applied clonidine. 4. Control tests indicate specific effects of NA and tizanidine application since similarly ionophoresed H+ ions did not change responses of gamma-motoneurones to stimulation of group II afferents, or only weakly enhanced their background discharges. Furthermore, serotonin ejected from a solution with a similar pH facilitated rather than depressed responses of gamma-motoneurones. 5. The results indicate that some antispastic effects of clonidine and tizanidine may be due to the depression of group II-evoked responses of gamma-motoneurones, resulting in weaker responses of muscle spindles to muscle stretches.

Adrenergic alpha-2 Receptor Agonists↗
PubMed1998

A leu-enkephalin depresses transmission from muscle and skin non-nociceptors to first-order feline spinal neurones.

1. The effects of an opioid (D-Ser-Leu-enkephalin-Thr; DSLET) were tested on synaptic actions of non-nociceptive afferents: group I and II muscle afferents and low-threshold skin afferents. They were tested on population EPSPs (field potentials) evoked in the dorsal horn and the intermediate zone of mid-lumbar segments, and on monosynaptically evoked responses of single interneurones at the same location. DSLET was applied locally (ionophoretically) at locations at which the field potentials were maximal and close to the selected neurones. 2. DSLET potently depressed transmission from group II muscle afferents and from low-threshold skin afferents. Transmission to neurones located in the dorsal horn or in the intermediate zone was depressed to a similar extent. The depression was readily antagonized by naloxone. Transmission from group Ia or Ib muscle afferents to neurones located in the intermediate zone was not affected, or was facilitated by DSLET. 3. The results show that DSLET has similar depressive actions on spinal neurones to monoamines, but its actions are more widespread. Like monoamines it affects transmission from nociceptors and group II muscle afferents, but in addition it gates transmission from low-threshold cutaneous afferents. Furthermore its effects do not appear to be restricted to interneurones at particular locations since it depressed responses of dorsal horn interneurones (gated by serotonin) as well as intermediate zone interneurones (gated by noradrenaline).

Analgesics↗
PubMed1998

Indications for coupling between feline spinocervical tract neurones and midlumbar interneurones.

The possibility of collateral segmental actions of spinocervical tract (SCT) neurones upon interneurones with input from cutaneous and group II muscle afferents was investigated in deeply anaesthetized cats. To this end, intracellular and/or extracellular recordings were made from 35 dorsal horn and 15 intermediate zone interneurones in midlumbar segments of the spinal cord and effects of stimulation of the ipsilateral dorso-lateral funiculus (DLF) at C3 and C1 levels, i.e. below and above the lateral cervical nucleus where axons of SCT cells terminate, were compared. The stimuli applied at the C3 segment were within the range of stimuli (50-100 microA) required for antidromic activation of SCT neurones in the same experiment. Those applied at the C segment (200-500 microA) were at least 3 times stronger than C3 stimuli. Under the same experimental conditions, long ascending and descending tract neurones (dorsal spino-cerebellar and rubro-spinal tract neurones) with axons in the DLF were activated at similar thresholds from the C and C3 segments. Intracellular recordings were made from 29 interneurones of which 19 (65%) were dorsal horn and 10 (35%) were intermediate zone interneurones. Excitatory postsynaptic potentials (EPSPs) evoked by single stimuli applied at the C3 segment, but not the C segment, were found in 14 (48%) of those interneurones; their latencies (3.0-5.7 ms) and frequency following with only minimal temporal facilitation were as required for potentials being evoked monosynaptically by the fastest conducting SCT neurones. Extracellular recordings were made from 30 interneurones (24 dorsal horn and 6 intermediate zone interneurones), and in these neurones spike potentials induced from the C3, but not from the C segment, were evoked only by short trains of stimuli. However, their latencies from the first effective stimulus (4.3-5.4 ms) were compatible with mono- or oligosynaptically mediated collateral actions of SCT neurones. They were found in 10 (33%) of the 30 investigated interneurones. Similar effects of C3 stimuli were found in similar proportions of dorsal horn interneurones and intermediate zone interneurones. Indications were also found for synaptic actions evoked by C3 stimuli that could not be attributed to direct collateral actions of SCT neurones. In some intracellularly recorded dorsal horn interneurones, short-latency EPSPs were evoked from the C3 segment by the 2nd or 3rd stimulus in the train, but not by single stimuli. In other dorsal horn and intermediate zone interneurones, inhibitory postsynaptic potentials (IPSPs) were evoked from the C3 segment at minimal latencies (2.7-3.2 ms), which might be too short to allow their mediation via SCT neurones. We conclude that SCT neurones might be used to forward information from muscle group II and cutaneous afferents not only to neurones in the lateral cervical nucleus and via them to thalamus and cerebral cortex but also to interneurones in spinal reflex pathways. Thereby reflex actions evoked from group II and cutaneous afferents might be co-ordinated with responses mediated by supraspinal neurones. We conclude also that dorsal horn and intermediate zone mid-lumbar interneurones might contribute to the previously reported di-and poly-synaptic excitation or inhibition of postsynaptic dorsal column (PSDC), spinothalamic tract (STT) and spinomesencephalic tract (SMT) neurones by collateral actions of SCT cells. Thereby these interneurones might contribute to the co-ordination of responses mediated by various populations of supraspinal neurones.

Animals↗
PubMed1997

A confocal and electron microscopic study of contacts between 5-HT fibres and feline dorsal horn interneurons in pathways from muscle afferents.

Morphological substrates of actions of serotonin upon dorsal horn interneurons with input from group II muscle afferents were investigated by using two experimental approaches. Twelve interneurons were intracellularly labelled with rhodamine-dextran, and serotoninergic fibres were identified by immunofluorescence. Appositions between the serotoninergic axons and these interneurons were examined with a dual-channel confocal microscope. A further four interneurons were intracellularly labelled with horseradish peroxidase, and serotoninergic axons were identified by immunocytochemistry; these neurons were prepared for combined light and electron microscopy. Confocal microscopy revealed serotoninergic varicosities in apposition to both cell bodies and dendrites. Similar total numbers of appositions were found on the soma, and on dendrites within 100 microm from the soma, on the most completely labelled neurons. The number of appositions on 100-microm segments of dendrites decreased with increasing distances from the soma (from 14.6 within 100 microm, to 3.8 and 2.4 at 100-300 microm, and more than 300 microm distances, respectively). Electron microscopic analysis of two neurons revealed that few of the apparent contacts on cell bodies were synaptic, but, in contrast, many varicosities apposed to proximal dendrites formed synapses. The evidence suggests that serotonin may have more powerful synaptic effects upon the dendrites of this class of dorsal horn interneurons than on their cell bodies.

Afferent Pathways↗
PubMed1997

Synaptic connections of dorsal horn group II spinal interneurons: synapses formed with the interneurons and by their axon collaterals.

Five dorsal horn interneurons with monosynaptic input from group II primary afferent fibres were physiologically characterized and intracellularly labelled with horseradish peroxidase. The cells were prepared for combined light and electron microscopy, and synaptic arrangements formed by axon collaterals of interneurons and synapses formed with their dendrites and somata were examined with the electron microscope. Immunogold reactions for gamma-aminobutyric acid, glycine and glutamate were performed to determine if these synapses were excitatory or inhibitory. Axon collaterals in lamina VI formed synapses with somata and dendrites of other neurons, and collaterals of one cell also formed axoaxonic synapses. It was concluded that one cell from the sample was inhibitory, whereas the remainder were probably excitatory. Dendrites and cell bodies of interneurons were contacted by several types of synaptic bouton. The first type of bouton displayed immunoreactivity for glutamate, the second type contained both gamma-aminobutyric acid and glycine, the third type contained glycine alone, and the fourth type contained gamma-aminobutyric acid alone. Some large glutamatergic boutons were postsynaptic to other boutons. Presynaptic boutons at these axoaxonic synapses always contained gamma-aminobutyric acid but a minority also contained glycine. The results of this study demonstrate the heterogeneity of dorsal horn group II interneurons and provide evidence that they include inhibitory and probably also excitatory neurons. Boutons originating from several chemically different classes of neuron are responsible for postsynaptic inhibition of these interneurons, and the presence of axoaxonic synapses indicates that their excitatory input is also controlled presynaptically.

Animals↗
PubMed1997

Modulation of responses of four types of feline ascending tract neurons by serotonin and noradrenaline.

Modulation of responses of four types of ascending tract cells by noradrenaline and serotonin was compared in order to investigate how information forwarded by these cells may be gated by monoaminergic tract neurons. Spinocervical tract, postsynaptic dorsal column and dorsal spinocerebellar tract neurons located in Clarke's column and in the dorsal horn were identified by their axonal projections. Noradrenaline and serotonin were applied ionophoretically close to a selected neuron, and their effects were tested on extracellularly recorded responses of this neuron to electrical stimulation of low-threshold skin afferents and group II muscle spindle afferents. The modulatory actions of noradrenaline and serotonin were estimated from changes in the number of responses evoked by 30 successive stimuli, the minimal latencies of these responses, and their firing frequency. All four populations of ascending tract neurons investigated were modulated by serotonin and noradrenaline, but not in the same way. The responses were most often depressed by noradrenaline and facilitated by serotonin, but in some types of neuron they were affected in the same direction. Transmission from low-threshold skin and group II muscle afferents changed in the same direction in some types of neuron but in the opposite direction in other types. The results indicate that transfer of information from skin and group II muscle afferents to supraspinal centres may be gated by descending monoaminergic pathways in a highly differentiated manner, and is adjusted to the requirements of various behavioural situations.

Animals↗
PubMed1996

How effective is integration of information from muscle afferents in spinal pathways?

Integration of information forwarded by group I and group II muscle afferents to premotor interneurones was estimated from spatial facilitation in oligosynaptic (most likely disynaptic) reflex pathways from these afferents. Indications for mutual facilitation of synaptic actions of group I and group II afferents have been found on both inhibitory and excitatory premotor interneurones but were easier to demonstrate in the inhibitory pathways. However, the facilitation appeared weak under our experimental conditions and depended critically upon the intensity and timing of the stimuli used to activate muscle afferents.

Afferent Pathways↗
PubMed1996

Antispastic effects of L-dopa.

Antispastic effects of the noradrenaline and dopamine precursor l-3,4-dihydroxyphelanine (L-dopa) were investigated in 11 subjects in which exaggerated stretch reflexes developed after spinal cord injuries. The effects were evaluated from changes in the electromyographic (EMG) response of the quadriceps muscle during tendon jerks evoked by standardized taps over the patellar tendon, in clonus and in resistance to passive movements of the limb. After administration of L-dopa, EMG responses occurring 30-150 ms after the tendon tap decreased to about 50% of control, and clinical tests revealed a marked decrease in the resistance to muscle stretches and in the degree of clonus. The effects were maximal within about 1 h. The depressive actions of L-dopa are interpreted as being exerted primarily at the spinal level, since they were evoked in paraplegics and tetraplegics. The results support the previous hypothesis that group II muscle afferents contribute to.the exaggerated stretch reflex in spastic patients because L-dopa depresses transmission from group II but not from group I muscle afferents. They also indicate the possibility of using L-dopa in the treatment of spastic patients.

Adolescent↗
PubMed1996

Synaptic relationships between serotonin-immunoreactive axons and dorsal horn spinocerebellar tract cells in the cat spinal cord.

Dorsal horn spinocerebellar tract cells were identified according to electrophysiological criteria in adult cats and labelled intracellularly with horseradish peroxidase. Sections containing labelled neurons were processed to reveal serotonin immunoreactivity and examined with light and electron microscopy. Numerous contacts were observed on cell bodies, and on proximal and intermediate parts of dendrites. Electron microscopic examination of contacts revealed that synaptic junctions were usually present at the region of apposition. It is concluded that serotonin has a postsynaptic action on dorsal horn spinocerebellar tract cells and that this action is mediated through conventional synapses.

Animals↗
PubMed1996

Morphometric ultrastructural evaluation of satellite cells in musculus gastrocnemius and musculus latissimus dorsi anterior of rats subjected to 7 day hypokinesia.

The investigations were undertaken to evaluate morphometrically the satellite cells (SC) of two muscles: the slow, musclus latissimus dorsi and the fast, musculus gastrocnemius from rats kept in hypokinetic conditions for seven days. The changes in both muscle were of similar character, they concerned a decrease in the Golgi apparatus, rough endoplasmic reticulum fractions and the number of ribosomes, and an increase in the relative volume of heterochromatin content. These findings seem to indicate a reduced activity of the SC. Differences were also demonstrated between the satellite cells in both examined muscles in the control group. They also suggest that the SC are not a homogeneous population as regards parameters evaluated in the present study.

Animals↗
PubMed1995

Organization of neuronal systems mediating presynaptic inhibition of group II muscle afferents in the cat.

1. The organization of neuronal systems mediating presynaptic control of transmission from group II muscle afferent fibres has been investigated by comparing the sources of presynaptic inhibition of fibres terminating in different segments of the spinal cord: fibres of the semitendinosus and lateral gastrocnemius muscle nerves terminating in the sacral segments and of the tibialis anterior and extensor digitorum longus muscle nerves terminating in the midlumbar segments. 2. Two measures of presynaptic inhibition were used: depolarization of the terminals of group II fibres (detected as changes in the excitability of single fibres to electrical stimuli) and a decrease in the effectiveness of their synaptic actions (detected as a decrease in the amplitude of monosynaptic field potentials evoked by group II muscle afferents). 3. Group II muscle afferents strongly depolarized all of the group II afferent fibres, while group I muscle afferents contributed to the depolarization of only a few. The majority of fibres were as effectively depolarized by cutaneous afferents as by the most effective muscle afferents. However, the effectiveness with which afferents of different nerves depolarized group II muscle afferent fibres in the sacral and midlumbar segments differed. The most effective afferents were those of nerves that provide the main input to dorsal horn interneurones in the same region of the spinal cord. The sources of depolarization of flexor and extensor fibres terminating in the same (sacral) segments were very similar. 4. The amplitudes of field potentials evoked by group II afferents were depressed by the same types of afferent as produced depolarization of group II afferent fibres. There was also a strong correlation between the effectiveness with which afferents of a given nerve induced depolarization of single fibres and depression of field potentials in the same segments. Since group II field potentials were depressed to a greater extent (by up to 90%) than group I field potentials (by no more than 20%) concurrently recorded in the intermediate zone of midlumbar segments, it appears that transmission from group II muscle afferents may be more strongly affected by presynaptic inhibition than that from group I muscle afferents. 5. The results suggest that the interneuronal systems responsible for the presynaptic control of transmission from group II muscle afferents have topographically restricted actions and an organization appropriate to a system of negative feedback control.

Afferent Pathways↗
PubMed1995

Interneurones mediating presynaptic inhibition of group II muscle afferents in the cat spinal cord.

1. To investigate whether dorsal horn interneurones with input from group II muscle afferents induce depolarization of sensory fibres, simultaneous recordings were made from single interneurones in the sacral segments and from sacral dorsal root filaments using the spike-triggered averaging technique. 2. The spike potentials of eighteen out of thirty-eight interneurones tested were followed by dorsal root potentials (DRPs). The DRPs occurred at latencies of 2 and 6-8 ms. Interneurones evoking DRPs at latencies of up to 2 ms are considered likely to be last-order interneurones in pathways of presynaptic inhibition, while those inducing DRPs at longer latencies are considered likely to be first-order interneurones. The former were activated by peripheral afferents with somewhat longer latencies than the latter. However, all interneurones were co-activated by group II muscle and cutaneous afferents, indicating that the depolarization of group II muscle afferents, which these afferents induce, may be mediated by the same interneurones. 3. DRPs evoked by electrical stimulation of peripheral nerves were recorded from both sacral and midlumbar dorsal root filaments. The amplitudes of these DRPs were closely related to the potency with which group II afferents of various nerves activate dorsal horn interneurones in the sacral and midlumbar segments and group II afferents contributed to them more effectively than group I afferents. The second stimulus in a train was more effective than the first, while a third stimulus had little additional effect, indicating that the interneurones involved are relatively easily activated. 4. Intraspinal stimuli applied within the dorsal horn, at the sites where the largest field potentials of group II origin were recorded, evoked distinct DRPs. However, the location of the first- and last-order interneurones in pathways of primary afferent depolarization (PAD) could not be differentiated by this approach because the same stimuli induced positive potentials, which masked the onset of DRPs and precluded localization of the sites from which DRPs might be evoked monosynaptically.

Afferent Pathways↗
PubMed1995

Depression of transmission from group II muscle afferents by electrical stimulation of the cuneiform nucleus in the cat.

The effects of short trains of electrical stimuli applied within the cuneiform nucleus and the subcuneiform region were examined on transmission from group I and group II muscle afferents to first-order spinal neurons. Variations in the effectiveness of transmission from these afferents were assessed from changes in the sizes of the monosynaptic component of extracellular field potentials evoked following stimulation of muscle nerves. Field potentials evoked from group II muscle afferents in the dorsal horn of the midlumbar and sacral segments and in the intermediate zone of the midlumbar segments were reduced when the test stimuli applied to peripheral nerves were preceded by conditioning stimulation of the cuneiform nucleus or the subcuneiform region. The depression occurred at conditioning-testing intervals of 20-400 ms, being maximal at intervals of 32-72 ms for dorsal horn potentials and 40-100 ms for intermediate zone potentials. At the shortest intervals, both group II and group I field potentials in the intermediate zone were depressed. Conditioning stimulation of the cuneiform nucleus depressed group II field potentials nearly as effectively as conditioning stimulation of the coerulear or raphe nuclei. We propose that the nonselective depression of transmission from group I and II afferents at short intervals is due to the activation of reticulospinal pathways by cells or fibers stimulated within the cuneiform area. We also propose that the selective depression of transmission from group II afferents at long intervals is mediated at least partly by monoaminergic pathways, in view of the similarity of the effects of conditioning stimulation of the cuneiform nucleus and of the brainstem monoaminergic nuclei and by directly applied monoamines (Bras et al. 1990). In addition, it might be caused by primary afferent depolarization mediated by non-monoaminergic fibers (Riddell et al. 1992).

Afferent Pathways↗
PubMed1995

Contacts between serotoninergic fibres and dorsal horn spinocerebellar tract neurons in the cat and rat: a confocal microscopic study.

Contacts between serotoninergic nerve fibres and dorsal horn dorsal spinocerebellar tract neurons were analysed in order to investigate the morphological basis of actions of serotonin upon dorsal spinocerebellar tract neurons. In a series of experiments dorsal spinocerebellar tract neurons were labelled with intracellularly injected rhodamine-dextran in the cat. The neurons were monosynaptically excited by group II muscle afferents and cutaneous afferents and were identified by antidromic activation following stimuli applied in the cerebellum. In the second series of experiments dorsal spinocerebellar tract neurons were labelled by retrograde transport of Fluorogold injected into the cerebellum in the rat. In both series, serotoninergic fibres were labelled by using a specific anti-serotonin antiserum and were revealed by immunofluorescence. Appositions between the serotoninergic fibres and the cells were inspected with a dual channel confocal microscope. The merged images obtained with the two channels of the microscope were viewed in single optical planes 2 microns apart and in rotated three-dimensional reconstructions. Serotoninergic nerve fibres were found in apposition to cell bodies of all feline dorsal spinocerebellar tract neurons (n = 7) and of 75% of rat dorsal spinocerebellar tract neurons (n = 90). The numbers of putative contacts on cell bodies varied between less than 100 and nearly 300 (mean 160) in the cat and between about five and 30 in the rat. Contacts with dendrites of feline neurons were seen on 96% of 72 dendrites within 300 microns from soma and on 91% of 23 dendrites at distances of 300-500 microns. The number of such contacts varied from less than five to 150 on a single dendrite within these ranges of distances. Their total number within 100 microns from the soma was comparable or exceeded the number of contacts on the soma.

Animals↗
PubMed1995

Effects of serotonin on dorsal horn dorsal spinocerebellar tract neurons.

Effects of ionophoretic application of serotonin and of one of its agonists were tested on responses of dorsal horn dorsal spinocerebellar tract neurons evoked by electrical stimulation of peripheral nerves. Both drugs depressed monosynaptically evoked actions of group II muscle afferents; they decreased the number and/or increased the latency of spike potentials evoked by these afferents. In contrast, synaptic actions of low-threshold cutaneous afferents (mono- or oligosynaptic) were facilitated in the majority of the neurons, as judged by decrease in the latency of spike potentials evoked by stimulation of a cutaneous nerve and/or an increase in the number of these potentials. It is proposed that facilitatory actions assist in maintaining tonic discharges of dorsal spinocerebellar tract neurons in some movements and that the selective control of group II input is used to correlate activity of spinal and supraspinal neurons. Both actions may be subserved by tight contacts between serotoninergic nerve fibres and dorsal spinocerebellar tract neurons, which have been revealed in a parallel study.

8-Hydroxy-2-(di-n-propylamino)tetralin↗