INTERINSTITUTE LABORATORY OF NEUROMUSCULAR
PLASTICITY
(Nencki Institute of
Experimental Biology and
and Biomedical Engineering)
|
Head:
Urszula SŁAWIŃSKA, Ph.D., D.Sc., Prof. Emeritus Teresa GÓRSKA, Ph.D., D.Sc., Staff:
Henryk MAJCZYŃSKI, Ph.D.,
Barbara CHOJNICKA, M.Sc. and
staff employed by the Anna CABAJ, M.Sc., Katarzyna MALESZAK, M.Sc. |
Our research is devoted to the investigation of the plasticity processes
in the neuromuscular system in rats and the neural control of locomotion.
Particularly the research involves the investigation of functional aspects of
muscle recovery after central and peripheral nervous system injury in young as
well as adult rats. Moreover, changes in the locomotor
function after spinal lesions of different extent and supraspinal
structures and the recovery of locomotor function in
rats are investigated. The main interest is given to search for the new
rehabilitation techniques that can stimulate the neuromuscular plasticity
mechanisms responsible for restitution of muscle function (i.e. intra spinal
neural transplantation, pharmacological treatment, intensive training and
rehabilitation) after various nervous system injuries.
To present examples of our research,
the results of several investigations carried out on adult and young rats to
study plasticity of neuromuscular system in matured and immatured
animals will be described.
In developing rats we demonstrated that neural circuitry in the spinal cord, although present,
is not yet fully developed in neonatal animals (Exp. Neurology 2002). This was shown in experiments performed on
developing rats (7-9 days old). In rat pups the hindlimb
postural function is immature and the animals do not lift their pelvis off the
ground. However exogenous L-DOPA administration (150 mg/kg) results in a marked
increase in postural activity of extensor muscles and episodes of locomotion
characterized by rhythmic reciprocal bursts of EMG activity in flexor and
extensor muscles. Nevertheless, quantitative analysis of EMG burst
characteristics indicated that the pattern of L-DOPA induced locomotion in immature
rats resembles only in some respects that observed in adults during spontaneous
locomotion. These results suggest that although the spinal neuronal circuits
that generate locomotor movements are already present
during the first week of life, but they are not yet fully functionally
developed.
Our next set of experiments show that this immaturity
might be crucial to observe functional readjustment of transposed extensor
muscle into the bed of antagonistic flexor muscle (J. Neuroscience 2002). In animals operated as young, the pattern
of transposed muscle activity recorded during locomotion was rearranged in line
with new functional demands after transposition, although the
“innate” soleus activity was still
preserved. In contrast to the extensor-like activity of normal soleus, the transposed muscle was activated during the
extension as well as the flexion of an ankle joint. In adult rats such surgery
resulted in rearranged activity of transposed soleus
muscle only in a few animals. We postulated that the immaturity of the nervous
system at the moment of surgery might be crucial for this readjustment.
In
the other set of experiments carried out on adult rats we demonstrated that after total spinal cord transection
the transplantation of embryonic neurons containing serotonin into the spinal
cord below the level of injury is able to influence its residual circuitry and
improve the recovery of motor function of hindlimbs (Exp Brain Res
2000). In our study the grafting of embryonic neural tissue of raphe nuclei region was used in the hope that the grafted serotonergic cells will integrate with the host neuronal
circuitry, establish appropriate connections and release the lacking serotonin
directly into the spinal cord below the total transection.
Our results provided evidence that the graft enhanced the recovery of hindlimb locomotor functions
after complete spinal cord transection. Moreover our results demonstrated that transplantation of serotonergic cells was effective even if carried out a long
time after spinal cord injury when the neuronal circuitry below the lesion was
already reorganized and changes in the effectors, i.e. motoneurons
and muscles, were well advanced.
Fig. 1. Locomotor-like hind limb movements induced by tail pinching
in paraplegic rats 3 months after spinal cord transection:
(A) paraplegic control rat, (B) paraplegic rat 2 months after intra spinal
grafting of embryonic serotoninergic cells
Selected publications:
1. Górska T., Zmysłowski W., Majczyński H. 1999. Overground
locomotion in intact rats: interlimb coordination,
support patterns and support phases duration. Acta Neurobiol. Exp., 59: 131-144
2. Sławińska
U., Majczyński H., Djavadian
R. 2000. Recovery of hindlimb motor function after spinal cord transection is enhanced by grafts of the embryonic raphe nuclei. Exp. Brain Res., 132: 27-38.
3.
Reserch in cooperation with
4. Tyč F.,
5. Navarrete R.,
Research in cooperation with
6. Jankowska E,
7. Hammar I.,Chojnicka
B., Jankowska E. 2002. Modulation
of responses of feline ventral spinocerebellar tract
neurons by monoamines. J. Comp. Neurol., 443:
298-309
8. Hammar
I, Sławińska U., Jankowska
E. 2002. A
comparison of post-activation depression of synaptic actions evoked by
different afferents at different locations in the feline spinal cord. Exp. Brain Res., 145:
126-129.
9. Jankowska
E., Sławińska U., Hammar
I. 2002. Differential
presynaptic inhibition in the dorsal horn and
intermediate zone of feline spinal cord. J. Physiol.
542 (1): 287-299.
10. Jankowska E., Sławińska U., Hammar I.
2002. On organization of a
neuronal network in pathways from group II muscle afferents in feline lumbar
spinal segments
J. Physiol. 542 (1): 301-314.