Evidence that some long-lasting effects of direct current in the rat spinal cord are activity-independent

The effects of trans-spinal direct current (DC) stimulation (tsDCS) on specific neuronal populations are difficult to elucidate, as it affects a variety of neuronal networks. However, facilitatory and depressive effects on neurons processing information from the skin and from muscles can be evaluated separately when weak (0.2-0.3 μA) DC is applied within restricted areas of the rat spinal cord. The effects of such local DC application were recently demonstrated to persist for at least 1 h, and to include changes in the excitability of afferent fibres and their synaptic actions. However, whether these effects require activation of afferent fibres in spinal neuronal pathways during DC application, i.e. whether they are activity-dependent or activity-independent, remained an open question. The aim of the present study was to address this question by analysing the effects of local DC application on monosynaptic actions of muscle and skin afferents (extracellular field potentials) and afferent fibre excitability. The results revealed that long-lasting post-polarization changes evoked without concomitant activation of afferent fibres replicate changes evoked by stimuli applied during, before and after polarization. The study leads to the conclusion that the reported effects are activity-independent. As this conclusion applies to the local effects of DC application in at least two spinal pathways and to the effects of both cathodal and anodal polarization, it indicates that some of the more widespread effects of trans-spinal and trans-cranial stimulation (both tsDCS and transcranial DC stimulation) may be activity-independent. The results may therefore contribute to the design of more specific DC applications in clinical practice.

On the distribution of information from muscle spindles in the spinal cord; how much does it depend on random factors?

Information forwarded by individual muscle spindles is modulated by the dynamic and static gamma motoneurons in a differentiated way, depending on the coupling between the fusimotor neurons and the various intrafusal muscle fibres. Further modulation of this information at the level of spinal neurons is also differentiated because connections between individual muscle spindles and their spinal target cells are quite variable. This review illustrates this variability with respect to the spinal trajectory of muscle spindle primary afferents and the distribution of their synaptic contacts on motoneurons and other spinal neurons. It also discusses some of the consequences of this variability for the processing of information from proprioceptors.

Presynaptic and postsynaptic effects of local cathodal DC polarization within the spinal cord in anaesthetized animal preparations

KEY POINTS

Trans-spinal DC stimulation affects both postsynaptic neurons and the presynaptic axons providing input to these neurons. In the present study, we show that intraspinally applied cathodal current replicates the effects of trans-spinal direct current stimulation in deeply anaesthetized animals and affects spinal neurons both during the actual current application and during a post-polarization period. Presynaptic effects of local cathodal polarization were expressed in an increase in the excitability of skin afferents (in the dorsal horn) and group Ia afferents (in motor nuclei), both during and at least 30 min after DC application. However, although the postsynaptic facilitation (i.e. more effective) activation of motoneurons by stimuli applied in a motor nucleus was very potent during local DC application, it was only negligible once DC was discontinued. The results suggest that the prolonged effects of cathodal polarization are primarily associated with changes in synaptic transmission.

ABSTRACT

The present study aimed to compare presynaptic and postsynaptic actions of direct current polarization in the spinal cord, focusing on DC effects on primary afferents and motoneurons. To reduce the directly affected spinal cord region, a weak polarizing direct current (0.1-0.3 μA) was applied locally in deeply anaesthetized cats and rats; within the hindlimb motor nuclei in the caudal lumbar segments, or in the dorsal horn within the terminal projection area of low threshold skin afferents. Changes in the excitability of primary afferents activated by intraspinal stimuli (20-50 μA) were estimated using increases or decreases in compound action potentials recorded from the dorsal roots or peripheral nerves as their measure. Changes in the postsynaptic actions of the afferents were assessed from intracellularly recorded monosynaptic EPSPs in hindlimb motoneurons and monosynaptic extracellular field potentials (evoked by group Ia afferents in motor nuclei, or by low threshold cutaneous afferents in the dorsal horn). The excitability of motoneurons activated by intraspinal stimuli was assessed using intracellular records or motoneuronal discharges recorded from a ventral root or a muscle nerve. Cathodal polarization was found to affect motoneurons and afferents providing input to them to a different extent. The excitability of both was markedly increased during DC application, although post-polarization facilitation was found to involve presynaptic afferents and some of their postsynaptic actions, but only negligibly motoneurons themselves. Taken together, these results indicate that long-lasting post-polarization facilitation of spinal activity induced by locally applied cathodal current primarily reflects the facilitation of synaptic transmission.

Presynaptic actions of transcranial and local direct current stimulation in the red nucleus

The main aim of the present study was to examine to what extent long-lasting subcortical actions of transcranial direct current stimulation (tDCS) may be related to its presynaptic actions. This was investigated in the red nucleus, where tDCS was recently demonstrated to facilitate transmission between interpositorubral and rubrospinal neurons. Changes in the excitability of preterminal axonal branches of interpositorubral neurons close to rubrospinal neurons were investigated during and after tDCS (0.2 mA) applied over the sensorimotor cortical area in deeply anaesthetized rats and cats. As a measure of the excitability, we used the probability of antidromic activation of individual interpositorubral neurons by electrical stimuli applied in the red nucleus. Our second aim was to compare effects of weak (≤1 μA) direct current applied within the red nucleus with effects of tDCS to allow the use of local depolarization in a further analysis of mechanisms of tDCS instead of widespread and more difficult to control depolarization evoked by distant electrodes. Local cathodal polarization was found to replicate all effects of cathodal tDCS hitherto demonstrated in the rat, including long-lasting facilitation of trans-synaptically evoked descending volleys and trisynaptically evoked EMG responses in neck muscles. It also replicated all effects of anodal tDCS in the cat. In both species, it increased the excitability of preterminal axonal branches of interpositorubral neurons up to 1 h post-tDCS. Local anodal polarization evoked opposite effects. We thus show that presynaptic actions of polarizing direct current may contribute to both immediate and prolonged effects of tDCS.

Facilitation of ipsilateral actions of corticospinal tract neurons on feline motoneurons by transcranial direct current stimulation

Ipsilateral actions of pyramidal tract (PT) neurons are weak but may, if strengthened, compensate for deficient crossed PT actions following brain damage. The purpose of the present study was to examine whether transcranial direct current stimulation (tDCS) can strengthen ipsilateral PT (iPT) actions; in particular, those relayed by reticulospinal neurons co-excited by axon collaterals of fibres descending in the iPT and contralateral PT (coPT) and of reticulospinal neurons descending in the medial longitudinal fascicle (MLF). The effects of tDCS were assessed in acute experiments on deeply anaesthetized cats by comparing postsynaptic potentials evoked in hindlimb motoneurons and discharges recorded from their axons in a ventral root, before, during and after tDCS. tDCS was consistently found to facilitate joint actions of the iPT and coPT, especially when they were stimulated together with the MLF. Both excitatory postsynaptic potentials and inhibitory postsynaptic potentials evoked in motoneurons and the ensuing ventral root discharges were facilitated, even though the facilitatory effects of tDCS were not sufficient for activation of motoneurons by iPT neurons alone. Facilitation outlasted single tDCS periods by at least a few minutes, and the effects evoked by repeated tDCS by up to 2 h. The results of this study thus indicate that tDCS may increase the contribution of iPT actions to the recovery of motor functions after injuries to coPT neurons, and thereby assist rehabilitation, provided that corticoreticular and reticulospinal connections are preserved.

Surface profilometry with binary axicon-vortex and lens-vortex optical elements

We report on the interesting effect observed with the diffractive binary element, which matches the property of an axicon and vortex lens. Binary phase coding simplifies the manufacturing process and gives additional advantages for metrology purposes. Under laser beam illumination, our element produces two waves: converging and diverging. Both waves carry a single optical vortex. We show that this special diffractive element can be used to set up a simple surface profilometer.

The proteasome in health and disease

The giant proteolytic factory called the proteasome came a long way from a biochemical curio to a major regulator of cellular physiology and a renowned drug target within the ubiquitin proteasome pathway (UPP). Thanks to availability of highly specific inhibitors of the proteasome, in less than twenty years it was possible to identify major transcription factors, cyclins, and products of oncogenes as crucial substrates for the UPP. Nine years passed since the FDA speedily approved bortezomib, the inhibitor of proteasome, for treatment of multiple myeloma. One year after its approval, the field was honored by awarding the Nobel Prize to Hershko, Ciechanover and Rose for introducing the concept of controlled proteolysis of ubiquitin-tagged substrates, with proteasome as the intracellular recycling facility. Taking into consideration the universal involvement of the proteasome in the life of all cells in human body, it comes to no surprise that the enzyme is deeply implicated in etiology, progression, diagnosis or cure of multiple diseases. Below we discuss some aspects of the involvement: from direct causative links to changes in proteasome properties that correlate with pathological conditions. We start with diseases collectively known as cancer, and with immune system-related pathologies. Here, the proteasome inhibitors are either already used in clinics, or undergo advanced preclinical screening. Then, we will continue with cardiovascular disorders, followed by aging. Changes of the proteasome make-up during aging may be a priming factor for neurodegenerative diseases, described last. We discuss the potential for proteasome regulation: inhibition, activation or specificity modulation, to successfully enter the clinical setting.

Subcortical effects of transcranial direct current stimulation in the rat

Transcranial direct current stimulation (tDCS) affects neurons at both cortical and subcortical levels. The subcortical effects involve several descending motor systems but appeared to be relatively weak, as only small increases in the amplitude of subcortically initiated descending volleys and a minute shortening of latencies of these volleys were found. The aim of the present study was therefore to evaluate the consequences of facilitation of these volleys on the ensuing muscle activation. The experiments were carried out on deeply anaesthetized rats without neuromuscular blockade. Effects of tDCS were tested on EMG potentials recorded from neck muscles evoked by weak (20-60 μA) single, double or triple stimuli applied in the medial longitudinal fascicle (MLF) or in the red nucleus (RN). Short latencies of these potentials were compatible with monosynaptic or disynaptic actions of reticulospinal and disynaptic or trisynaptic actions of rubrospinal neurons on neck motoneurons. Despite only weak effects on indirect descending volleys, the EMG responses from both the MLF and the RN were potently facilitated by cathodal tDCS and depressed by anodal tDCS. Both the facilitation and the depression developed relatively rapidly (within the first minute) but both outlasted tDCS and were present for up to 1 h after tDCS. The study thus demonstrates long-lasting effects of tDCS on subcortical neurons in the rat, albeit evoked by an opposite polarity of tDCS to that found to be effective on subcortical neurons in the cat investigated in the preceding study, or for cortical neurons in the humans.

[Potential exposure to silver nanoparticles during spraying preparation for air-conditioning cleaning]

BACKGROUND

Unique properties of engineered nanomaterials (ENMs) and products made of them have contributed to a rapid progress in the production and application of ENMs in different branches of industry and in factories with different production scale. Bearing in mind that nano-objects (nanoplates, nanofibres, nanoparticles), emitted during ENM production and application, can cause many diseases, even those not yet recognized, extensive studies have been carried all over the world to assess the extent of exposure to nano-objects at workstations and related health effects in workers employed in ENM manufacture and application processes.

MATERIAL AND METHODS

The study of potential exposure to silver nanoparticles contained in the preparation for air-conditioning cleaning (Nano Silver from Amtra Sp. z o.o.) involved the determination of concentrations and size distribution of particles, using different devices, allowing for tracing changes in a wide range of dimensions, from nano-size (10 nm) to micrometer-size (10 pm), of the particles which are usually inhaled by humans.

RESULTS AND CONCLUSIONS

The results of the study shows that even during a short-term spraying of Nano Silver preparation (for 10 s) at the distance of 52 cm from the place of preparation spraying--particles of 10 nm-10 microm can be emitted into in the air. During a three-fold preparation spraying in similar conditions differences in concentration increase were observed, but in each case the particles remained in the air for a relatively long time.

Evidence for long-lasting subcortical facilitation by transcranial direct current stimulation in the cat

The main aim of the study was to examine the effects of transcranial polarization on neurons in two descending motor systems, rubro- and reticulospinal. Anodal DC current was applied through an electrode in contact with the skull over the contralateral sensori-motor cortex, against an electrode placed between the skull and the ipsilateral temporal muscles in deeply anaesthetized cats. Its effects were estimated from changes in descending volleys evoked by electrical stimuli applied in the red nucleus (RN), medial longitudinal fascicle (MLF; to reticulospinal fibres) and the pyramidal tract (PT; to corticospinal or corticoreticular fibres). The descending volleys were recorded from the surface of the spinal cord at a cervical level. Rubrospinal neurones were activated either directly or indirectly, via interpositorubral fibres. Reticulospinal neurons were likewise activated directly and indirectly, via other reticulospinal or corticospinal fibres. Transcranial polarization facilitated transsynaptic activation of both rubrospinal and reticulospinal neurons, shortening the latency of the indirect descending volleys and/or increasing them, Direct activation of descending axons was much less affected. The facilitation of all subcortical neurons examined was potentiated by repeated applications of transcranial direct current stimulation (tDCS) and outlasted the polarization by at least 1-2 h, replicating tDCS effects on indirect activation of cortical neurons. The results indicate that the beneficial effects of tDCS on motor performance in humans may be due to more efficient activation of not only cortical but also subcortical neuronal systems. Combined actions of tDCS on cortical and subcortical neurones might thus further improve recovery of motor functions during rehabilitation after central injuries. 249/250.

Interactions between spinal interneurons and ventral spinocerebellar tract neurons

Recent evidence indicates that ventral spinocerebellar tract (VSCT) neurons do not merely receive information provided by spinal interneurons but may also modulate the activity of these interneurons. Hence, interactions between them may be mutual. However, while it is well established that spinal interneurons may provide both excitatory and inhibitory input to ascending tract neurons, the functional consequences of the almost exclusively inhibitory input from premotor interneurons to subpopulations of VSCT neurons were only recently addressed. These are discussed in the first part of this review. The second part of the review summarizes evidence that some VSCT neurons may operate both as projection neurons and as spinal interneurons and play a role in spinal circuitry. It outlines the evidence that initial axon collaterals of VSCT neurons target premotor inhibitory interneurons in disynaptic reflex pathways from tendon organs and muscle spindles (group Ia, Ib and/or II muscle afferents) to motoneurons. By activating these interneurons VSCT neurons may evoke disynaptic IPSPs in motoneurons and thus facilitate inhibitory actions of contralateral muscle afferents on motoneurons. In this way they may contribute to the coordination between neuronal networks on both sides of the spinal cord in advance of modulatory actions evoked via the cerebellar control systems.

A survey of spinal collateral actions of feline ventral spinocerebellar tract neurons

The aim of this study was to identify spinal target cells of spinocerebellar neurons, in particular the ventral spinocerebellar tract (VSCT) neurons, giving off axon collaterals terminating within the lumbosacral enlargement. Axons of spinocerebellar neurons were stimulated within the cerebellum while searching for most direct synaptic actions on intracellularly recorded hindlimb motoneurons and interneurons. In motoneurons the dominating effects were inhibitory [inhibitory postsynaptic potentials (IPSPs) in 67% and excitatory postsynaptic potentials (EPSPs) in 17% of motoneurons]. Latencies of most IPSPs indicated that they were evoked disynaptically and mutual facilitation between these IPSPs and disynaptic IPSPs evoked by group Ia afferents from antagonist muscles and group Ib and II afferents from synergists indicated that they were relayed by premotor interneurons in reflex pathways from muscle afferents. Monosynaptic EPSPs from the cerebellum were accordingly found in Ia inhibitory interneurons and intermediate zone interneurons with input from group I and II afferents but only oligosynaptic EPSPs in motoneurons. Monosynaptic EPSPs following cerebellar stimulation were also found in some VSCT neurons, indicating coupling between various spinocerebellar neurons. The results are in keeping with the previously demonstrated projections of VSCT neurons to the contralateral ventral horn, showing that VSCT neurons might contribute to motor control at a spinal level. They might thus play a role in modulating spinal activity in advance of any control exerted via the cerebellar loop.

Pressure as a denaturing agent in studies of single-point mutants of an amyloidogenic protein human cystatin c

Recently, we presented a convenient method combining a deuterium-hydrogen exchange and electrospray mass spectrometry for studying high-pressure denaturation of proteins (Stefanowicz et al., Biosci Rep 2009; 30:91-99). Here, we present results of pressure-induced denaturation studies of an amyloidogenic protein-the wild-type human cystatin C (hCC) and its single-point mutants, in which Val57 residue from the hinge region was substituted by Asn, Asp or Pro, respectively. The place of mutation and the substituting residues were chosen mainly on a basis of theoretical calculations. Observation of H/D isotopic exchange proceeding during pressure induced unfolding and subsequent refolding allowed us to detect differences in the proteins stability and folding dynamics. On the basis of the obtained results we can conclude that proline residue at the hinge region makes cystatin C structure more flexible and dynamic, what probably facilitates the dimerization process of this hCC variant. Polar asparagine does not influence stability of hCC conformation significantly, whereas charged aspartic acid in 57 position makes the protein structure slightly more prone to unfolding. Our experiments also point out pressure denaturation as a valuable supplementary method in denaturation studies of mutated proteins.

Excitatory inputs to four types of spinocerebellar tract neurons in the cat and the rat thoraco-lumbar spinal cord

The cerebellum receives information from the hindlimbs through several populations of spinocerebellar tract neurons. Although the role of these neurons has been established in electrophysiological experiments, the relative contribution of afferent fibres and central neurons to their excitatory input has only been estimated approximately so far. Taking advantage of differences in the immunohistochemistry of glutamatergic terminals of peripheral afferents and of central neurons (with vesicular glutamate transporters VGLUT1 or VGLUT2, respectively), we compared sources of excitatory input to four populations of spinocerebellar neurons in the thoraco-lumbar spinal cord: dorsal spinocerebellar tract neurons located in Clarke's column (ccDSCT) and in the dorsal horn (dhDSCT) and ventral spinocerebellar tract (VSCT) neurons including spinal border (SB) neurons. This was done on 22 electrophysiologically identified intracellularly labelled neurons in cats and on 80 neurons labelled by retrograde transport of cholera toxin b subunit injected into the cerebellum of rats. In both species distribution of antibodies against VGLUT1 and VGLUT2 on SB neurons (which have dominating inhibitory input from limb muscles), revealed very few VGLUT1 contacts and remarkably high numbers of VGLUT2 contacts. In VSCT neurons with excitatory afferent input, the number of VGLUT1 contacts was relatively high although VGLUT2 contacts likewise dominated, while the proportions of VGLUT1 and VGLUT2 immunoreactive terminals were the reverse on the two populations of DSCT neurons. These findings provide morphological evidence that SB neurons principally receive excitatory inputs from central neurons and provide the cerebellum with information regarding central neuronal activity.

Crystallization and preliminary X-ray diffraction analysis of Val57 mutants of the amyloidogenic protein human cystatin C

Human cystatin C (hCC) is a low-molecular-mass protein (120 amino-acid residues, 13 343 Da) found in all nucleated cells. Its main physiological role is regulation of the activity of cysteine proteases. Biologically active hCC is a monomeric protein, but all crystallization efforts have resulted in a dimeric domain-swapped structure. Recently, two monomeric structures were reported for cystatin C variants. In one of them stabilization was achieved by abolishing the possibility of domain swapping by the introduction of an additional disulfide bridge connecting the two protein domains (Cys47-Cys69). In the second structure, reported by this group, the monomeric hCC fold was preserved by stabilization of the conformationally constrained loop (L1) by a single-amino-acid substitution (V57N). To further assess the influence of changes in the sequence and properties of loop L1 on the dimerization propensity of cystatin C, two additional hCC mutants were obtained: one with a residue favoured in β-turns (V57D) and another with proline (V57P), a residue that is known to be a structural element that can rigidify but also broaden turns. Here, the expression, purification and crystallization of V57D and V57P variants of recombinant human cystatin C are described. Crystals were grown by the vapour-diffusion method. Several diffraction data sets were collected using a synchrotron source at the Advanced Photon Source, Argonne National Laboratory, Chicago, USA.

Do spinocerebellar neurones forward information on spinal actions of neurones in the feline red nucleus?

We recently demonstrated that feline ventral spinocerebellar tract (VSCT) neurones monitor descending commands for voluntary movements initiated by pyramidal tract (PT) neurones as well as locomotor movements relayed by reticulospinal (RS) neurones. The aim of the present study was to examine whether VSCT neurones likewise monitor descending commands from the red nucleus (RN). Extracellular records from the spinal border (SB) subpopulation of VSCT neurons revealed that a third (31%) of SB neurones may be discharged by trains of stimuli applied in the RN. Moreover, when RN stimuli failed to discharge SB neurones they facilitated activation of some of these neurones by RS and/or PT neurones, while activation of other SB neurones was depressed. We propose that the facilitation and depression of actions of RS neurones by RN neurones might serve to reflect a higher or lower excitability of motoneurones and therefore a likely higher or lower efficacy of the RS descending commands, prompting the cerebellum to adjust the activation of reticulospinal neurones. Activation of SB neurones by RN stimuli alone would also allow monitoring and adjusting the RN descending commands. Intracellular records from SB neurones revealed both monosynaptic and disynaptic EPSPs and disynaptic IPSPs evoked by RN stimuli. The disynaptic actions remained following transection of axons of reticulospinal neurones within the medullary longitudinal fascicle (MLF) and were therefore taken to be relayed primarily by spinal neurones, in contrast to EPSPs and IPSPs evoked by PT stimuli found to be relayed by reticulospinal rather than spinal neurones.

Processing information related to centrally initiated locomotor and voluntary movements by feline spinocerebellar neurones

Feed-back information on centrally initiated movements is processed at both supraspinal and spinal levels and is forwarded by a variety of neurones. The aim of the present study was to examine how descending commands relayed by reticulospinal neurones are monitored by a population of spinocerebellar tract neurones. Our main question was whether a spinal border (SB) subpopulation of ventral spinocerebellar tract (VSCT) neurones monitor actions of reticulospinal neurones with input from the mesencephalic locomotor region (MLR) as well as from pyramidal tract (PT) neurones. In the majority of intracellularly recorded SB neurons, stimuli applied in the MLR and in the medullary pyramids evoked EPSPs in parallel with EPSPs evoked by stimulation of axons of reticulospinal neurones in the medial longitudinal fascicle (MLF). In extracellularly recorded neurones short trains of stimuli applied in the ipsilateral and contralateral pyramids potently facilitated discharges evoked from the MLF, as well as EPSPs recorded intracellularly. In both cases the facilitation involved the disynaptic but not the monosynaptic actions. These results indicate that reticulospinal neurones activating SB neurones (or more generally VSCT neurones) are co-excited by axon-collaterals of other reticulospinal neurones and by fibres stimulated within the MLR and PTs. The study leads to the conclusion that these spinocerebellar neurones monitor descending commands for centrally initiated voluntary as well as locomotor movements relayed by reticulospinal neurones. Thereby they may provide the cerebellum with feed-back information on the likely outcome of these commands and any corrections needed to avoid errors in the issuing movements.

A structured observational method to assess dermal exposure to manufactured nanoparticles DREAM as an initial assessment tool

Preliminary results of inventories of exposure scenarios for nanomaterials have indicated possible dermal exposure. Within the NANOSH project focused on occupational safety and health aspects of nanotechnology a shortened version of the observational DeRmal Exposure AssessMent (DREAM) method was used as an initial method to assess dermal exposure. A total of 45 tasks (such as bagging, dumping, and cleaning) involving different manufactured nanoparticles (MNPs) such as carbon nanotubes, fumed silica, and cerium oxide, were observed in industrial and research facilities. In 39 tasks potential dermal exposure (that is, exposure of the skin and clothing) was likely to occur. Exposure resulted from different routes, including direct contact with MNPs as well as the deposition or transfer of MNPs. The survey showed it is both feasible and useful to assess the potential dermal exposure using shortened DREAM questionnaires.

Do premotor interneurons act in parallel on spinal motoneurons and on dorsal horn spinocerebellar and spinocervical tract neurons in the cat?

It has previously been established that ventral spinocerebellar tract (VSCT) neurons and dorsal spinocerebellar tract neurons located in Clarke's column (CC DSCT neurons) forward information on actions of premotor interneurons in reflex pathways from muscle afferents on α-motoneurons. Whether DSCT neurons located in the dorsal horn (dh DSCT neurons) and spinocervical tract (SCT) neurons are involved in forwarding similar feedback information has not yet been investigated. The aim of the present study was therefore to examine the input from premotor interneurons to these neurons. Electrical stimuli were applied within major hindlimb motor nuclei to activate axon-collaterals of interneurons projecting to these nuclei, and intracellular records were obtained from dh DSCT and SCT neurons. Direct actions of the stimulated interneurons were differentiated from indirect actions by latencies of postsynaptic potentials evoked by intraspinal stimuli and by the absence or presence of temporal facilitation. Direct actions of premotor interneurons were found in a smaller proportion of dh DSCT than of CC DSCT neurons. However, they were evoked by both excitatory and inhibitory interneurons, whereas only inhibitory premotor interneurons were previously found to affect CC DSCT neurons [as indicated by monosynaptic excitatory postsynaptic potentials (EPSPs) and inhibitory postsynaptic potentials (IPSPs) in dh DSCT and only IPSPs in CC DSCT neurons]. No effects of premotor interneurons were found in SCT neurons, since monosynaptic EPSPs or IPSPs were only evoked in them by stimuli applied outside motor nuclei. The study thus reveals a considerable differentiation of feedback information provided by different populations of ascending tract neurons.