| 1. |
- Jankowska, Elzbieta, et al.
(författare)
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A relay for input from group II muscle afferents in sacral segments of the cat spinal cord.
- 1993
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Ingår i: The Journal of Physiology. - : Wiley. - 0022-3751 .- 1469-7793. ; 465, s. 561-580
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Tidskriftsartikel (refereegranskat)abstract
- 1. A neuronal relay for input from group II afferents of hindlimb muscle nerves has been found in the previously little explored sacral segments of the cat spinal cord. 2. Electrical stimulation of group II muscle afferents of a number of nerves evoked negative potentials on the surface (cord dorsum potentials) and population postsynaptic potentials (field potentials) within the sacral segments. The largest potentials were evoked by stimulation of the posterior biceps‐semitendinosus and triceps surae nerves which evoke much smaller potentials in other segments. Group II afferents of other nerves, notably those which have their main relay within the middle lumbar segments, were much less effective. 3. The sites at which cord dorsum and field potentials evoked by group II muscle afferents were recorded varied in relation to the external topography of the L7‐S2 spinal segments but were consistent in their location relative to the pudendal motor nucleus (Onuf's nucleus). Potentials evoked by group II afferents of the posterior biceps and semitendinosus nerves peaked at a level corresponding to the rostral half of Onuf's nucleus and potentials evoked by afferents of the gastrocnemius nerves peaked just rostral to this nucleus. The largest field potentials (of 0.5‐1.0 mV) were recorded within the dorsal horn. Field potentials in the intermediate zone were much smaller (< 0.3 mV) and were seen less frequently. 4. Evidence was obtained that the dorsal horn field potentials are to a great extent evoked monosynaptically by the fast conducting fraction of group II muscle afferents: (i) they were evoked at short latencies (2.4‐2.7 ms from the stimulus; 1.3‐1.7 ms from group I components of afferent volleys and 0.5‐0.7 ms from group II components of these volleys), (ii) the conduction times of impulses in the fastest conducting fraction of group II afferents, between the sacral segments (where these impulses were induced by intraspinal stimuli) and the peripheral nerves, were only about 0.5 ms shorter than the latencies of field potentials recorded at the site of intraspinal stimulation and evoked by stimulation of the same peripheral nerves and, (iii) the field potentials followed repetitive stimuli without temporal facilitation. 5. Negative cord dorsum and field potentials were also evoked by small stretches of the semitendinosus and triceps surae muscles. Although they were smaller than potentials evoked by electrical stimulation of sensory fibres and appeared at longer latencies, their presence is consistent with a contribution of muscle spindle afferents to the actions of group II muscle afferents within the sacral segments.(ABSTRACT TRUNCATED AT 400 WORDS) © 1993 The Physiological Society
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| 2. |
- Jankowska, Elzbieta, et al.
(författare)
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Gating of transmission to motoneurones by stimuli applied in the locus coeruleus and raphe nuclei of the cat.
- 1993
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Ingår i: The Journal of Physiology. - : Wiley. - 0022-3751 .- 1469-7793. ; 461, s. 705-722
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Tidskriftsartikel (refereegranskat)abstract
- 1. Neuronal systems activated by stimulation in the region of the locus coeruleus/subcoeruleus (LC/SC) and raphe nuclei have previously been shown to depress transmission from group II muscle afferents in regions of the midlumbar spinal segments in which premotor interneurones are located. The aim of the present investigation was to determine the extent to which such depression is paralleled by depression of the reflex actions of group II afferents on motoneurones. 2. The effects of short trains of conditioning electrical stimuli applied within the LC/SC and raphe nuclei were examined on postsynaptic potentials (PSPs) evoked by group I and group II muscle afferents in hindlimb motoneurones. The effects were examined over a wide range of conditioning‐test intervals but particular emphasis was placed on the effects produced at long intervals (> 100 ms) since such effects are more likely to be mediated by the descending noradrenergic and serotonergic neurones of the LC/SC and raphe nuclei which are of slow conduction velocity. In addition, conditioning stimuli alone evoked PSPs in motoneurones (with latencies of 7‐15 ms and a duration of 50‐80 ms) and effects evoked at short conditioning‐test intervals might therefore have been secondary to changes in motoneurone membrane properties. 3. At conditioning‐test intervals between 100 and 350 ms synaptic actions of group II origin were strongly and consistently depressed. Both EPSPs and IPSPs were affected, two‐thirds of those tested being reduced in amplitude by 50% or more. A similar depression was exerted on PSPs evoked from the quadriceps and deep peroneal nerves mediated predominantly by interneurones located in the midlumbar segments and on PSPs evoked from the hamstring and triceps surae nerves mediated by interneurones located in more caudal segments. It is thus concluded that neuronal systems activated by stimuli applied in the LC/SC and raphe nuclei are capable of gating transmission in all those interneuronal pathways which mediate the reflex actions of group II afferents on motoneurones in anaesthetized animals. © 1993 The Physiological Society
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| 3. |
- Jankowska, Elzbieta, et al.
(författare)
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Interneurones in pathways from group II muscle afferents in sacral segments of the feline spinal cord.
- 1994
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Ingår i: The Journal of Physiology. - : Wiley. - 0022-3751 .- 1469-7793. ; 475, s. 455-468
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Tidskriftsartikel (refereegranskat)abstract
- 1. Properties of dorsal horn interneurones that process information from group II muscle afferents in the sacral segments of the spinal cord have been investigated in the cat using both intracellular and extracellular recording. 2. The interneurones were excited by group II muscle afferents and cutaneous afferents but not by group I muscle afferents. They were most effectively excited by group II afferents of the posterior biceps, semitendinosus, triceps surae and quadriceps muscle nerves and by cutaneous afferents running in the cutaneous femoris, pudendal and sural nerves. The earliest synaptic actions were evoked monosynaptically and were very tightly locked to the stimuli. 3. EPSPs evoked monosynaptically by group II muscle afferents and cutaneous afferents of the most effective nerves were often cut short by disynaptic IPSPs. As a consequence of this negative feedback the EPSPs gave rise to single or double spike potentials and only a minority of interneurones responded with repetitive discharges. However, the neurones that did respond repetitively did so at a very high frequency of discharges (0.8‐1.2 ms intervals between the first 2‐3 spikes). 4. Sacral dorsal horn group II interneurones do not appear to act directly upon motoneurones because: (i) these interneurones are located outside the area within which last order interneurones have previously been found and (ii) the latencies of PSPs evoked in motoneurones by stimulation of the posterior biceps and semitendinosus, cutaneous femoris and pudendal nerves (i.e. the main nerves providing input to sacral interneurones) are compatible with a tri‐ but not with a disynaptic coupling. Spatial facilitation of EPSPs and IPSPs following synchronous stimulation of group II and cutaneous afferents of these nerves shows, however, that sacral interneurones may induce excitation or inhibition of motoneurones via other interneurones. 5. Comparison of the properties of group II interneurones in the sacral segments with those of previously studied group II interneurones in the midlumbar segments leads to the conclusion that these two populations of neurones are specialized for the processing of information from different muscles and skin areas. In addition, equivalents of only one of the two subpopulations of midlumbar interneurones have been found at the level of the pudendal nucleus: neurones with input from group II but not from group I muscle afferents. Neurones integrating information from group I and II muscle afferents and in direct contact with motoneurones thus seem to be scarce in the sacral segments.(ABSTRACT TRUNCATED AT 400 WORDS) © 1994 The Physiological Society
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| 4. |
- Jankowska, Elzbieta, et al.
(författare)
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Morphology of interneurones in pathways from group II muscle afferents in sacral segments of the cat spinal cord.
- 1993
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Ingår i: The Journal of comparative neurology. - : Wiley. - 0021-9967. ; 337:3, s. 518-28
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Tidskriftsartikel (refereegranskat)abstract
- The morphology of 12 sacral interneurones with peripheral input from group II muscle afferents was analyzed after intracellular injection of horseradish peroxidase (HRP). The neurones were located in Rexed's laminae III-V overlying the pudendal (Onuf's) motor nucleus. The interneurones had medium sized elongated somata and dendrites projecting radially. All of the interneurones were funicular neurones and fell into two categories depending on whether their axons ran within the dorsal part of the lateral funiculus (DLF; n = 7) or within the ventral funiculus, or the ventral part of the lateral funiculus (VF or VLF; n = 4). The latter were located more rostrally. Within the DLF similar proportions of stem axons and secondary axonal branches descended and ascended. Within the VF and VLF all of the axons ascended. Collaterals of axons running in the DLF arborized primarily within the dorsal horn and the intermediate zone; none were found to approach the motor nuclei. In contrast, collaterals of axons running in the VF/VLF arborized in both the intermediate zone and the ventral horn and passed close to the motor nuclei. We conclude that sacral interneurones with group II input are morphologically nonhomogenous and that only those located most rostrally might have direct actions upon motoneurones. Both the axonal projections and the input (from group II but not from group I muscle afferents and from skin afferents) of sacral interneurones indicate that they are homologous to dorsal horn group II interneurones in the midlumbar segments. They appear, however, to form part of more local neuronal networks than their midlumbar counterparts.
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| 5. |
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| 6. |
- Riddell, J S, et al.
(författare)
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Ascending tract neurones processing information from group II muscle afferents in sacral segments of the feline spinal cord.
- 1994
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Ingår i: The Journal of physiology. - 0022-3751. ; 475:3, s. 469-81
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Tidskriftsartikel (refereegranskat)abstract
- 1. Ascending tract neurones located in the dorsal horn of sacral segments of the spinal cord have been investigated by extracellular and intracellular recording in the anaesthetized cat. The aim was to determine whether information from group II afferents that terminate within the sacral segments is conveyed to supraspinal structures and which types of neurones are involved. 2. A considerable proportion of ascending tract neurones found in the dorsal horn in the same segments as the pudendal (Onuf's) motor nucleus were excited by group II muscle afferents. The great majority (93%) of these neurones had axons ascending in ipsilateral funiculi. Spinocervical tract neurones constituted the largest proportion (82%) of such neurones, while very few spinocerebellar tract and propriospinal neurones and no postsynaptic dorsal column neurones were found among them. 3. In addition to activation by group II muscle afferents all of the neurones were strongly excited by cutaneous afferents. The most potent excitation was evoked by afferents of the posterior biceps-semitendinosus and gastrocnemius muscle nerves and by afferents of the cutaneous femoris, sural and pudendal nerves. The latencies of intracellularly recorded excitatory potentials were indicative of a high incidence of monosynaptic coupling between the afferents and ascending tract neurones. 4. The highly effective monosynaptic excitation of spinocervical tract neurones in the sacral segments by group II afferents is in contrast to the weak disynaptically mediated actions of group II afferents on such neurones in the L6-L7 segments but comparable to the actions of group II afferents on ascending tract neurones in the midlumbar segments. 5. Both the patterns of peripheral input and the latencies of synaptic actions in ascending tract neurones were similar to those in interneurones at the same locations (accompanying report). Similar information is therefore likely to be processed by both categories of neurones. 6. The role of sacral spinocervical tract neurones as a system for transmitting information from group II muscle afferents to supraspinal centres and the potential contribution of this system to the perception of limb position are discussed.
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| 7. |
- Riddell, J. S., et al.
(författare)
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Depolarization of group II muscle afferents by stimuli applied in the locus coeruleus and raphe nuclei of the cat.
- 1993
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Ingår i: The Journal of Physiology. - : Wiley. - 0022-3751 .- 1469-7793. ; 461, s. 723-741
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Tidskriftsartikel (refereegranskat)abstract
- 1. Electrical stimuli applied in the locus coeruleus/subcoeruleus (LC/SC) and raphe nuclei produce a profound depression of transmission in reflex pathways from group II muscle afferents. The present experiments were performed to determine whether presynaptic inhibitory mechanisms contribute to these effects. 2. Changes in the excitability of afferent terminals to electrical stimuli have been used as an indication of primary afferent depolarization (PAD) produced by conditioning stimuli applied within the LC/SC and raphe nuclei and, for comparison, in the nucleus ruber. Group II afferents originating from ankle flexor muscles and terminating in the midlumbar segments were used for testing. 3. Clear changes in excitability were observed in fourteen of nineteen group II fibres in which the effects of conditioning stimuli applied in the LC/SC were tested and in twelve of seventeen fibres in which the effects of stimuli applied within the raphe nuclei were tested. By comparison, only one of the twelve fibres tested with conditioning stimuli applied to the nucleus ruber was found to be influenced. These effects matched those of the same conditioning stimuli on field potentials evoked by group II afferents at the location at which the terminals of group II fibres were stimulated. 4. Stimuli applied in the LC/SC and in the raphe nuclei both produced a mean decrease in threshold stimulus current of 19%. These effects are comparable to those produced by the most effective volleys in peripheral afferent which, in the same fibres, produced a mean decrease in threshold stimulus current of 24%. 5. In all cases (twelve) in which the effects of stimuli applied in the LC/SC and raphe nuclei were tested on the same group II fibre, either both or neither were found to be effective. This strengthens previous indications that some populations of neurones might be activated by stimuli applied in each of these regions of the brain. 6. In contrast to group II afferents, group Ia afferents investigated in the same experiments were only exceptionally affected. Of seven fibres tested with stimuli applied in the LC/SC, six with stimuli applied in the raphe nuclei and seven with stimuli applied in the nucleus ruber, only one fibre showed any clear change in threshold and this was a single fibre which was similarly affected by stimuli in all three sites. 7. It is concluded that presynaptic inhibitory mechanisms contribute to the depression of transmission in spinal reflex pathways from group II muscle afferents produced by stimulation in the LC/SC and raphe nuclei. © 1993 The Physiological Society
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