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Biomedical subjects

E Jankowska

Publications and source records attributed to E Jankowska.

At least 127 records · Page 7Linked to original sources
PubMed1983

Shared reflex pathways from Ib tendon organ afferents and Ia muscle spindle afferents in the cat.

The possibility was investigated that group Ia muscle spindle afferents and group Ib tendon organ afferents influence spinal motoneurones via shared neuronal pathways. Mutual facilitation of actions of these afferents at a premotoneuronal level has been taken as evidence that they use the same interneurones to evoke post-synaptic potentials (p.s.p.s) in motoneurones. Inhibitory p.s.p.s (i.p.s.p.s) or excitatory p.s.p.s (e.p.s.p.s) were evoked in motoneurones by selective activation of group Ia afferents or group Ib afferents. P.s.p.s following stimulation of both Ia and Ib afferents were then compared with the arithmetic sum of p.s.p.s evoked by each of them separately. When the former were larger the difference was used as a measure of synaptic actions mediated by interneurones co-excited by Ia and Ib afferents. Both excitatory and inhibitory pathways to motoneurones have been found to be shared by Ia and Ib afferents, although the proportion of interneurones actually used in common by these afferents could not be established. The latencies of post-synaptic actions mediated by such interneurones indicated that they were evoked disynaptically or trisynaptically. The study leads to two main conclusions: that group Ia muscle spindle afferents, and in consequence also fusimotor systems, may modulate the reflex action of tendon organs, and that the two groups of afferents are a source of information in a common feed-back system.

Action Potentials↗
PubMed1983

Shared reflex pathways of group I afferents of different cat hind-limb muscles.

The convergence of group I muscle afferents of different muscle origin onto interneurones in spinal reflex pathways has been investigated using the technique of spatial facilitation of the transmission from afferents to motoneurones. The investigated pathways are those of non-reciprocal inhibition and of oligosynaptic excitation of motoneurones. Extensive convergence has been found of group I afferents from muscles operating at the same and different joints onto the interneurones interposed in both excitatory and inhibitory, disynaptic and trisynaptic pathways to motoneurones. Convergence has been found between muscle spindle Ia and/or tendon organ Ib afferents from different muscles, thereby extending observations on convergence of these subgroups of group I afferents from the same muscles. The results show that group I afferents of different muscles influence motoneurones via shared neuronal pathways and that transmission from these afferents is influenced by afferents originating in other muscles. The afferent information forwarded to individual motoneurones is therefore the ensemble picture of the length and tension of many muscles.

Action Potentials↗
PubMed1983

Inhibition of dorsal spinocerebellar tract cells by interneurones in upper and lower lumbar segments in the cat.

The topographical distribution of interneurones mediating disynaptic inhibition of dorsal spinocerebellar tract (d.s.c.t.) cells from group I muscle afferents in the cat was investigated using both physiological and morphological techniques. Lesions of either the dorsal funiculi or of the lateral and ventral funiculi were made between L4 and L5 segments in two groups of cats. I.p.s.p.s. evoked from group I afferents were seen after both these lesions, showing that the i.p.s.p.s were evoked by interneurones located more caudally as well as by interneurones in the same segments as Clarke's column. Distribution of the caudally located interneurones in the lower lumbar segments was investigated after marking these interneurones with horseradish peroxidase retrogradely transported from Clarke's column. The horseradish peroxidase was injected along L3-L4 segments of Clarke's column in two cats with transected dorsal funiculi. The marked cells were found in L5, L6, L7 and S1 segments, with a highest density in L6 and L7. They were seen in laminae V, VI and VII. A search was made for interneurones which could be antidromically invaded following stimuli applied in Clarke's column and were monosynaptically excited by group I afferents. Such interneurones were found at locations corresponding to laminae V-VI of Rexed. The latencies of antidromic and orthodromic responses were within ranges allowing them to mediate disynaptic inhibition of d.s.c.t. cells.

Animals↗
PubMed1983

The same interneurones mediate inhibition of dorsal spinocerebellar tract cells and lumbar motoneurones in the cat.

The aim of the study was to investigate whether inhibition of dorsal spinocerebellar tract (d.s.c.t.) cells evoked from group I afferents is mediated by the same interneurones which mediate the non-reciprocal inhibition of hind-limb motoneurones. The origin of inhibition of d.s.c.t. cells from group I afferents was compared in intact preparations, after lesions of the dorsal funiculi (when it could only be mediated by lower lumbar interneurones) and after lesions of the lateral and ventral funiculi (when it would be expected to be evoked by upper lumbar interneurones). In all three preparations extensors were the most common source of inhibition, as in motoneurones. Lower lumbar interneurones inhibiting d.s.c.t. cells were found to be co-excited by group I (Ia and/or Ib) and cutaneous and joint afferents, and by rubrospinal tract fibres, as are interneurones mediating inhibition of motoneurones. Co-excitation by group I and rubrospinal fibres was also found for upper lumbar interneurones. I.p.s.p.s were evoked in hind-limb motoneurones from within Clarke's column in cats with the dorsal funiculi cut between L4 and L5 segments; they were evoked at thresholds as low as 2 microA, i.e. by stimuli with very local actions. The latencies of these i.p.s.p.s were short enough to allow them to be evoked monosynaptically via axonal branches of the same interneurones which projected to Clarke's column. Correspondingly, i.p.s.p.s were evoked in d.s.c.t. cells from within motor nuclei in L7 segments; they were evoked at similarly low thresholds and with similar latencies. In confirmation of previous reports i.p.s.p.s of Ia origin evoked in d.s.c.t. cells were not found to be depressed by Renshaw cells, which excludes their mediation by interneurones responsible for Ia reciprocal inhibition. The study leads to the conclusion that the inhibition of d.s.c.t. cells from group I afferents is, at least in part, collateral to the non-reciprocal inhibition of lumbar motoneurones.

Animals↗
PubMed1983

Post-synaptic potentials in a population of motoneurones following activity of single interneurones in the cat.

The technique of recording post-synaptic potentials from a population of motoneurones, by recording from ventral roots perfused with isotonic sucrose, has been applied to investigate the action of single last-order interneurones; the target motoneurones were in either caudal L7 or S1 segments. Using spike-triggered averaging, the inhibitory action of 70% of previously identified last-order interneurones (Renshaw cells and lamina VII Ia inhibitory interneurones) has been detected. Previous observations had suggested that interneurones mediating disynaptic non-reciprocal inhibition from group I muscle afferents should be characterized by (i) location in laminae V-VI, (ii) monosynaptic group I input and (iii) ascending collateral axonal projection to upper lumbar segments. 65% of interneurones with these characteristics were found to inhibit motoneurones. In addition, spike-triggered averaging from this group of laminae V-VI interneurones sometimes revealed a depolarizing potential which preceded the inhibitory potential evoked by the interneurone. The depolarizing potential is interpreted as being due to the action of some presynaptic fibres which branch to innervate both the investigated interneurones and motoneurones.

Animals↗
PubMed1983

Inhibitory interactions between interneurones in reflex pathways from group Ia and group Ib afferents in the cat.

A hypothesis has been verified that laminae V-VI interneurones which mediate non-reciprocal inhibition of motoneurones from group I muscle afferents have collateral actions on other laminae V-VI interneurones. Stimulation within the areas of projection of these inhibitory interneurones in motor nuclei and in Clarke's column would be expected to give rise to monosynaptic i.p.s.p.s in interneurones with disynaptic i.p.s.p.s from group I afferents if the hypothesis were correct. Intracellular records were made from eighty-five laminae V-VI interneurones with input from group Ia muscle spindle and/or group Ib tendon organ afferents. Weak intraspinal stimuli applied in motor nuclei in L7 and S1 segments, or in the lateral funiculus just caudal to Clarke's column in L4, were found to evoke monosynaptic i.p.s.p.s in seventy-two interneurones. These i.p.s.p.s were systematically correlated with disynaptic inhibition from group Ia or Ib afferents but not from other fibres. Such monosynaptic i.p.s.p.s evoked by intraspinal stimuli were seen in forty-two interneurones which themselves projected to the level of Clarke's column and therefore (on the basis of previous evidence) should mediate inhibition of motoneurones. For seven of these interneurones it was also shown directly that they projected to motor nuclei. The inhibition of such interneurones demonstrates mutual interactions between those interneurones which are interposed in inhibitory pathways from group I afferents. Only indirect indications have been obtained for inhibition of interneurones in the excitatory pathways.

Animals↗
PubMed1982

Effects of 4-aminopyridine on synaptic transmission in the cat spinal cord.

An analysis was made of effects of 0.1-1.0 mg/kg 4-aminopyridine (4-AP) i.v. on excitatory and inhibitory spinal reflex pathways in lightly anaesthetized or decerebrated cats. The effects appeared within the first minutes of the injection, reached maximum after about 10-15 min and remained stable during at least several hours. 4-AP enhanced the following synaptic actions on motoneurones: monosynaptic excitation from Ia afferents and descending tracts, disynaptic and polysynaptic excitation from group Ib, group II, cutaneous and high threshold muscle afferents, disynaptic inhibition from Ia and Ib afferents and recurrent and polysynaptic inhibition from different afferents. 4-AP also increased primary afferent depolarization and excitation of ascending tract cells by peripheral stimuli. In the case of the disynaptic inhibitory pathways it has been shown that 4-AP may enhance the excitation of the interposed interneurones but it also increases the action of these interneurones on the motoneurones; monosynaptic inhibition evoked in motoneurones by electrical stimulation of the axons of the inhibitory interneurones was used as a test response in these experiments. No indications were found of direct effects of 4-AP on excitability of afferent fibres or motoneurones to electrical stimuli. No systematic changes were either found in the membrane potential of motoneurones or in the duration of action potentials of these neurones or primary afferents. It is therefore concluded that small doses of 4-AP enhance synaptic transmission in the spinal cord by an action at a presynaptic level.

4-Aminopyridine↗
PubMed1981

Integration in descending motor pathways controlling the forelimb in the cat. 7. Effects from the reticular formation on C3-C4 propriospinal neurones.

Effects of stimulation in the medullary reticular formation (RF) on C3-C4 propriospinal neurones (PNs) were investigated in two series of experiments: (1) indirectly by analyzing how propriospinal transmission to forelimb motoneurones is modified by reticular stimuli; (2) directly by intracellular recording from C3-C4 neurones, which were identified as propriospinal by their antidromic activation from the C6 segment. Propriospinally mediated disynaptic EPSPs evoked in motoneurones from the pyramid (Pyr) and the red nucleus (NR) were effectively facilitated by conditioning stimulation in the RF with a time course of facilitation indicating monosynaptic linkage to the PNs. Propriospinally mediated trisynaptic IPSPs were facilitated less regularly and sometimes instead depressed by conditioning stimulation in the RF. The depression is at least partly due to inhibition of the first order PNs. Recording from C3-C4 PNs revealed that many of them were excited or inhibited by single stimuli in the RF. The brief latency of the EPSPs evoked in these neurones shows monosynaptic linkage from fast reticulospinal fibres. Some IPSPs were similarly monosynaptically evoked from fast fibres and observations are presented suggesting that longer latency IPSPs are monosynaptically mediated by slower fibres. Facilitation of propriospinal transmission to motoneurones as well as the EPSPs and IPSPs in PNs were evoked from a region within or close to the nucleus reticularis gigantocellularis. Convergence of monosynaptic EPSPs from Pyr, NR, tectum, and RF was common in C3-C4 PNs. Linear summation of the EPSPs from RF with those evoked from cortico-, rubro-, or tectospinal tracts shows that the former are not due to stimulation of collaterals which the latter tracts may have in RF. Mediation of the EPSPs and IPSPs by descending, rather than by antidromically activated ascending fibres, was indicated by temporal facilitation produced by RF stimuli, subliminal for evoking monosynaptic PSPs in the PNs. Stimulation of the labyrinth did not evoke disynaptic PSPs in any of the PNs investigated. It is concluded that the C3-C4 PNs projecting to forelimb motoneurones can be excited not only from the cortico-, rubro-, and tectospinal tracts (Illert et at. 1977, 1978) but also by reticulospinal fibres.

Animals↗
PubMed1981

Common interneurones in reflex pathways from group 1a and 1b afferents of knee flexors and extensors in the cat.

1. Input from group I afferents of knee flexors and extensors to interneurones in Rexed's laminae V-VI in the cat spinal cord was analysed by use of intracellular recording and electrical stimulation of the nerves to differentiate between group Ia and Ib synaptic actions. The aim was to find out if these interneurones may mediate synaptic actions of both group Ia and Ib afferents. 2. 28% of the forty-nine neurones analysed were excited by both group Ia and group Ib afferents; 32% were inhibited by both and 35% were excited by the one and inhibited by the other. Taking into account all of these actions, input from both subgroups of group I afferents was found in nearly 60% of neurones. Most were also excited and/or inhibited by group I afferents of ankle and toe extensors. 3. Selective (excitatory and/or inhibitory) input from Ia afferents was found in 18% and from Ib afferents in 22% of the neurones. 4. Excitation was evoked from Ia afferents of either knee flexors or extensors but not from both. In several of the neurones Ia i.p.s.p.s were, however, evoked from both posterior biceps-semitendinosus and quadriceps. 5. Intracellular staining with horseradish peroxidase revealed axonal projections of laminae V-VI interneurones to motor nuclei as well as to the intermediate zone, ipsilateral as well as contralateral. No correlation was found between patterns of input from group I afferents and axonal projections, and interneurones co-excited by Ia and Ib afferents were among these with different axonal projections.

Afferent Pathways↗
PubMed1981

Common interneurones in reflex pathways from group 1a and 1b afferents of ankle extensors in the cat.

1. Input from group I afferents of ankle and toe extensors, other muscles, skin nerves and descending tracts to interneurones of Rexed's laminae V-VI in the cat spinal cord was analysed using intracellular recording from these interneurones. Adequate stimuli (muscle stretches) were used to activate selectively group Ia muscle spindle afferents of triceps surae and plantaris while other fibre systems were excited electrically. 2. Ia and Ib afferents of ankle and toe extensors were found to co-excite, co-inhibit or exert opposite synaptic actions in 41, 33, and 50% of the analysed interneurones, respectively. Taking into account both excitatory and inhibitory input from these two groups of afferents, 64% of the interneurones appeared to be used in common in reflex pathways from muscle spindles and tendon organs of ankle and toe extensors. 3. Selective input from Ib afferents of triceps surae and plantaris (excitation and/or inhibition) was found in 36% of the interneurones; there was evidence for a similarly selective input from Ia afferents. 4. A great majority (over 90%) of the interneurones excited by group I afferents were also inhibited by group I afferents, from either the same or other muscles. 5. Both monosynaptic and disynaptic e.p.s.p.s from Ia and/or Ib afferents from other muscles and from fibres in the ipsilateral funiculi were found in a great proportion of the same interneurones, together with disynaptic e.p.s.p.s from low threshold cutaneous afferents. 6. Intracellular staining with horseradish peroxidase revealed four different patterns of axonal projections of the analysed interneurones: (i) projections to motor nuclei and the intermediate region, (ii and III) projections only to the intermediate region, locally or combined with projections to different rostro-caudal levels, and (iv) projections to the opposite side of the spinal cord. 7. A large proportion of interneurones projecting to motor nuclei displayed input from both Ia and Ib afferents although such an input was a feature of interneurones with other projections as well. No systematic differences in the input from group I afferents were found for interneurones with different axonal projections. In contrast disynaptic e.p.s.p.s of cutaneous origin and monosynaptic e.p.s.p.s upon stimulation of ipsilateral spinal tracts appeared predominantly in interneurones projecting to motor nuclei.

Afferent Pathways↗
PubMed1981

Pattern of 'non-reciprocal' inhibition of motoneurones by impulses in group Ia muscle spindle afferents in the cat.

1. Inhibitory post-synaptic potentials (i.p.s.p.s) evoked by adequate stimulation of group Ia muscle spindle afferents of triceps surae and plantaris and by near-threshold electrical stimulation of quadriceps and hamstring nerves were recorded in a number of motoneurone species. The aim of the study was to compare the pattern of non-reciprocal Ia inhibitory actions on hind-limb motoneurones with the pattern of inhibition evoked from group Ib tendon organ afferents.2. In all the motoneurone species analysed in which i.p.s.p.s were evoked by electrical stimulation maximal for both group Ia and Ib afferents of triceps surae and plantaris, they were also evoked when these muscles were stretched and the amplitude of the stretch (10-35 mum) was below threshold for Ib afferents; 70-100% of motoneurones with Ib i.p.s.p.s showed stretch-evoked i.p.s.p.s. The stretch-evoked i.p.s.p.s appeared with latencies compatible with disynaptic and trisynaptic linkage. Since these latencies were too short to allow their mediation by group II afferents the i.p.s.p.s are attributed to a selective action of Ia afferents. The i.p.s.p.s did not appear after the nerves to triceps surae and plantaris had been cut.3. Electrical stimulation of quadriceps and hamstring nerves which was near threshold for Ia afferents and well below threshold for either the Ib component of the incoming volley or group II afferents, similarly evoked non-reciprocal i.p.s.p.s. They were found in those motoneurones in which inhibition was evoked by stimulation maximal for group I afferents. Such Ia i.p.s.p.s were evoked both in homonymous motoneurones and in motoneurones of four other hind-limb muscles. Their latencies corresponded to di- and trisynaptic coupling.4. In some motoneurones of the pretibial flexors (anterior tibial, extensor digitorum longus and peroneus longus), disynaptic i.p.s.p.s evoked from triceps surae and/or plantaris which were depressed by a conditioning ventral root stimulation (i.e. Ia reciprocal i.p.s.p.s) were followed by trisynaptic i.p.s.p.s which were not depressed in this way (Ia ;non-reciprocal' i.p.s.p.s). It thus appears that the same motoneurones may be inhibited by impulses in group Ia afferents via different spinal pathways.5. The study leads to the conclusion that the non-reciprocal inhibition from group Ia muscle spindle afferents operates in parallel with the inhibition from group Ib tendon organ afferents in all motoneurone species tested.

Animals↗
PubMed1981

Oligosynaptic excitation of motoneurones by impulses in group Ia muscle spindle afferents in the cat.

1. Intracellular recording from hind-limb motoneurones was used to investigate whether di- and trisynaptic (oligosynaptic) excitatory post-synaptic potentials (e.p.s.p.s) are evoked from group Ia muscle spindle afferents in those motoneurones in which such potentials are evoked from Ib tendon organ afferents or entire group I afferents. Ia afferents of triceps surae and plantaris were activated either selectively by single brief stretches of these muscles, or together with Ib afferents by electrical stimuli applied to the nerves.2. Muscle stretches below threshold for Ib afferents (10-35 mum) evoked e.p.s.p.s which appeared with latencies compatible with disynaptic and trisynaptic coupling between the afferents and the motoneurones. The latencies of a majority of these e.p.s.p.s were too short to allow their mediation by group II afferents, if any were activated by the applied stretches. They were also too short to be compatible with effects attributable to dorsal root reflexes. These e.p.s.p.s are thus attributed to oligosynaptic actions of Ia afferents.3. Stretch-evoked di- and trisynaptic Ia e.p.s.p.s were found in 83% of motoneurones in which e.p.s.p.s were evoked by stimuli which activated both Ia and Ib afferents; in five motoneurone species they were found in more than 90%. These observations lead to the conclusion that group Ia muscle spindle afferents evoke not only inhibitory but also excitatory actions in parallel with group Ib tendon organ afferents.4. The distribution of Ia oligosynaptic stretch-evoked excitation from ankle and toe extensor muscles was compared with the distribution of Ia non-reciprocal inhibition as described by Jankowska, McCrea & Mackel (1981b). Excitation pre-dominated in posterior biceps-semitendinosus motoneurones and inhibition in other species of motoneurones investigated, except those of intrinsic foot muscles (tibial motoneurones); similar proportions of the latter showed excitation and inhibition.5. Occurrence of oligosynaptic e.p.s.p.s as well as inhibitory post-synaptic potentials (i.p.s.p.s) of Ia origin in some motoneurone species, and in particular in individual motoneurones, is indicative of a number of reflex pathways between group I afferents and these motoneurones. Furthermore, the disappearance of some of the e.p.s.p.s evoked by near-threshold electrical stimulation following stronger stimuli indicates interactions between various functional groups of interneurones mediating group I actions.

Animals↗
PubMed1980

Crosses and uncrossed synaptic actions on motoneurones of back muscles in the cat.

Intracellular recording from motoneurones of back muscles was used to analyze their synaptic input. The sample included motoneurones located in Th13--L2 spinal segments, identified by their antidromic invasion following stimulation of medial, intermediate and lateral branches of the dorsal rami. The motoneurones were monosynaptically excited from lowest threshold ipsilateral afferents and from ipsilateral descending spinal tracts. Polysynaptic EPSPs and/or IPSPs were evoked in them from higher threshold ipsilateral and contralateral afferents and from descending spinal tracts, and recurrent inhibition was evoked from ipsilateral motor axon collaterals. There was no evidence of crossed disynaptic inhibition from group I afferents, or crossed recurrent inhibition of these neurones. Supplementary records from another group of neurones in Th13--L2 segments, unidentified but likely to innervate other back or abdominal muscles, showed monosynaptic and polysynaptic PSPs of the same origin, and in addition disynaptic IPSPs and disynaptic EPSPs from contralateral ventral roots. The crossed IPSPs had features of the crossed recurrent IPSPs, while the crossed EPSPs appeared to be more likely evoked by some afferents passing via the ventral roots. Generally, the input to the investigated neurones showed greatest similarities to the input to motoneurones of neck muscles and differed from that reported for tail motoneurones.

Afferent Pathways↗