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1
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Bilateral projection of neurones of the C6 segment to S1 and S2 segments of the spinal cord in the cat

100%
Krutki P.
Acta Neurobiologiae Experimentalis
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1997
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vol. 57
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issue 1
1-9
EN
Sacral projections of neurones located in the C6 segment of the spinal cord were electrophysiologically investigated in alpha- chloralose anaesthetized cats. The cell bodies were found mainly in lamina VIII and in the ventromedial part of lamina VII of the C6 segment. At the thoracic level their axons descended in lateral funiculi, mostly on both sides and only exceptionally contra or ipsilaterally. However, bilateral projection to sacral segments was less frequent (25 neurones). It is concluded that axons terminate at different levels on both sides of the spinal cord and only part of them project bilaterally to S1/S2 segments. Conduction velocities calculated for all the axons varied from 38 to 80 m/s and were significantly slower for their distal parts. Therefore it is suggested that descending axons send collaterals at various spinal levels. The presented data indicate the importance of these neurones for interlimb coordination.
2
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Electrophysiological investigation of spino-olivary projections originating from sacral segments of the cat spinal cord

63%
Mrowczynski W., Krutki P.
Acta Neurobiologiae Experimentalis
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2001
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vol. 61
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issue 4
319-324
EN
Ascending projections of sacral spinal cord neurones (S1-S2) to the dorsal accessory olivary nucleus (DAO) were electrophysiologically investigated in 3 adult cats under deep -chloralose anaesthesia. Antidromic action potentials were recorded extracellularly from 19 cells following stimulation of their axons in both the contralateral dorsal accessory olivary nucleus (coDAO) and the contralateral lateral funiculus at the level of lower thoracic segments (Th13). Two groups of neurones were identified in the gray matter of S1-S2 segments: one distributed in the medial part of Rexed?s laminae VI and VII (n=5), the other located in the ventromedial part of lamina VIII (n=14). Axonal conduction velocities of neurones investigated were comprised in the range 32-55 m/s. A significant decrease of conduction velocity was observed in each case when distal and proximal parts of the axon were compared. Our research confirmed anatomical data concerning spino-olivary neurones originating from sacral segments. However, we suggest that axons of this pathway give off collaterals to other spinal or supraspinal centres.
3
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Afferent input from distal forelimb nerves to branching spinoreticular-spinocerebellar neurones in the cat

63%
Krutki P., Mrowczynski W.
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EN
Patterns of afferent connections from receptors of the distal forelimb were investigated in neurones located in C6-C7 segments of the spinal cord with branching axons projecting to the lateral reticular nucleus and the cerebellum. Experiments were made on five adult cats under alpha-chloralose anaesthesia. After antidromic identification, EPSPs and IPSPs were recorded from 22 neurones following stimulation of deep radial, superficial radial, median and ulnar nerves. Both excitatory and inhibitory effects were found in the majority of the cells, however, in 2 cases no synaptic actions were recorded. EPSPs were evoked from group I or II muscle, or cutaneous afferents ? mostly monosynaptically. IPSPs from muscle, cutaneous or flexor reflex afferents were mostly polysynaptic. Seven various types of convergence were established in the cells investigated. Significance of parallel transmission of integrated information from various receptors of the distal forelimb to the reticular formation and cerebellum is discussed.
4
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Projections of laminae IV-VI neurones located in the S2 segment of the spinal cord to the C6 segment and the cerebellum in the cat

51%
Mrowczynski K., Grottel K., Krutki P.
Acta Neurobiologiae Experimentalis
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1998
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vol. 58
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issue 2
103-111
EN
Ascending projections of neurones of the second sacral segment (S2) of the spinal cord to the sixth cervical segment (C6) and to the cerebellum were electrophysiologically investigated in eight adult cats under alpha-chloralose anaesthesia. Antidromic potentials recorded from 44 neurones following stimulation of their axons in the grey matter of the C6 segment as well as in the contralateral restiform body (coRB) showed evidence of both supraspinal and propriospinal projections. About one third of neurones (15) ascended to the cerebellum through the coRB and gave off collaterals to the C6 segment, while the rest (29) terminated exclusively at the level of the C6 segment. The cell bodies were found mainly in central parts of Rexed's laminae IV, V and VI while axons ran in lateral funiculi. Axonal conduction velocities measured between S2 and C6 segments were in the range of 42-78 m/s. A decrease of conduction velocity above the Th13 and C6 segments was found in most axons suggesting that they give some collaterals at spinal as well as supraspinal levels.
5
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Double stimulation modulates afterhyperpolarization phase following action potentials evoked in rat motoneurones

51%
Mrowczynski W., Krutki P., Celichowski J.
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EN
The influence of a pair of stimuli running in time sequence between 5-10 ms (a doublet) on the basic parameters of antidromic action potentials was studied in rat motoneurones. Electrophysiological experiments were based on stimulation of axons in the sciatic nerve and intracellular recording of antidromic action potentials from individual motoneurones located in L4-L5 segments of the spinal cord. The following parameters were analyzed after application of a single stimulus and a doublet: amplitude and duration of the antidromic spike, amplitude, total duration, time to minimum, half-decay time of the afterhyperpolarization (AHP). It was demonstrated that application of a pair of stimuli resulted in: (1) a prolongation of action potentials, (2) a prolongation of the total duration and half-decay time of the AHP, (3) a decline of the time to minimum of the AHP, (4) an increase of the AHP amplitude of the spike evoked by the second stimulus. Significant differences in AHP parameters were found either in fast or slow motoneurones. We suppose that doublet-evoked changes in the AHP amplitude and duration are linked to intrinsic properties of individual motoneurones and may lead to the prolongation of the time interval to subsequent motoneuronal discharges during voluntary activity.
6
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Branching neurones in the cervical spinal cord with axons that reach sacral segments and the lateral reticular nucleus. An electrophysiological study in the cat

51%
Krutki P., Grottel K., Mrowczynski W.
Acta Neurobiologiae Experimentalis
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1999
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vol. 59
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issue 4
279-285
EN
Branching neurones in the cervical enlargement of the spinal cord were electrophysiologically studied in alpha-chloralose anaesthetized cats with the method of antidromic activation of axons. Stimulating electrodes were placed bilaterally at levels of lower thoracic and sacral segments and in the lateral reticular nucleus (LRN), ipsilaterally to the recording sites in C6/C7 segments. Thirty-nine out of a total one hundred neurones could be classified as bidirectional neurones with both descending and ascending collaterals. In the remaining cases only long descending projections to spinal segments were found. Comparison of conduction velocities measured in descending branches revealed no significant differences between individual neurones. On the other hand, descending collaterals of double direction neurones conducted impulses considerably faster than their axonal branches ascending to LRN. Our results suggest that parallel transmission of information to various, spinal or supraspinal centres of the nervous system is more common than reported before.
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